diff options
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/Kconfig | 241 | ||||
| -rw-r--r-- | kernel/rcu/Kconfig.debug | 82 | ||||
| -rw-r--r-- | kernel/rcu/Makefile | 14 | ||||
| -rw-r--r-- | kernel/rcu/rcu.h | 551 | ||||
| -rw-r--r-- | kernel/rcu/rcu_segcblist.c | 428 | ||||
| -rw-r--r-- | kernel/rcu/rcu_segcblist.h | 138 | ||||
| -rw-r--r-- | kernel/rcu/rcuperf.c | 761 | ||||
| -rw-r--r-- | kernel/rcu/rcutorture.c | 2141 | ||||
| -rw-r--r-- | kernel/rcu/srcutiny.c | 206 | ||||
| -rw-r--r-- | kernel/rcu/srcutree.c | 1312 | ||||
| -rw-r--r-- | kernel/rcu/sync.c | 240 | ||||
| -rw-r--r-- | kernel/rcu/tiny.c | 239 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 4187 | ||||
| -rw-r--r-- | kernel/rcu/tree.h | 500 | ||||
| -rw-r--r-- | kernel/rcu/tree_exp.h | 811 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 2693 | ||||
| -rw-r--r-- | kernel/rcu/update.c | 977 |
17 files changed, 15521 insertions, 0 deletions
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig new file mode 100644 index 000000000..9210379c0 --- /dev/null +++ b/kernel/rcu/Kconfig @@ -0,0 +1,241 @@ +# +# RCU-related configuration options +# + +menu "RCU Subsystem" + +config TREE_RCU + bool + default y if !PREEMPT && SMP + help + This option selects the RCU implementation that is + designed for very large SMP system with hundreds or + thousands of CPUs. It also scales down nicely to + smaller systems. + +config PREEMPT_RCU + bool + default y if PREEMPT + help + This option selects the RCU implementation that is + designed for very large SMP systems with hundreds or + thousands of CPUs, but for which real-time response + is also required. It also scales down nicely to + smaller systems. + + Select this option if you are unsure. + +config TINY_RCU + bool + default y if !PREEMPT && !SMP + help + This option selects the RCU implementation that is + designed for UP systems from which real-time response + is not required. This option greatly reduces the + memory footprint of RCU. + +config RCU_EXPERT + bool "Make expert-level adjustments to RCU configuration" + default n + help + This option needs to be enabled if you wish to make + expert-level adjustments to RCU configuration. By default, + no such adjustments can be made, which has the often-beneficial + side-effect of preventing "make oldconfig" from asking you all + sorts of detailed questions about how you would like numerous + obscure RCU options to be set up. + + Say Y if you need to make expert-level adjustments to RCU. + + Say N if you are unsure. + +config SRCU + bool + help + This option selects the sleepable version of RCU. This version + permits arbitrary sleeping or blocking within RCU read-side critical + sections. + +config TINY_SRCU + bool + default y if SRCU && TINY_RCU + help + This option selects the single-CPU non-preemptible version of SRCU. + +config TREE_SRCU + bool + default y if SRCU && !TINY_RCU + help + This option selects the full-fledged version of SRCU. + +config TASKS_RCU + def_bool PREEMPT + select SRCU + help + This option enables a task-based RCU implementation that uses + only voluntary context switch (not preemption!), idle, and + user-mode execution as quiescent states. + +config RCU_STALL_COMMON + def_bool ( TREE_RCU || PREEMPT_RCU ) + help + This option enables RCU CPU stall code that is common between + the TINY and TREE variants of RCU. The purpose is to allow + the tiny variants to disable RCU CPU stall warnings, while + making these warnings mandatory for the tree variants. + +config RCU_NEED_SEGCBLIST + def_bool ( TREE_RCU || PREEMPT_RCU || TREE_SRCU ) + +config CONTEXT_TRACKING + bool + +config CONTEXT_TRACKING_FORCE + bool "Force context tracking" + depends on CONTEXT_TRACKING + default y if !NO_HZ_FULL + help + The major pre-requirement for full dynticks to work is to + support the context tracking subsystem. But there are also + other dependencies to provide in order to make the full + dynticks working. + + This option stands for testing when an arch implements the + context tracking backend but doesn't yet fullfill all the + requirements to make the full dynticks feature working. + Without the full dynticks, there is no way to test the support + for context tracking and the subsystems that rely on it: RCU + userspace extended quiescent state and tickless cputime + accounting. This option copes with the absence of the full + dynticks subsystem by forcing the context tracking on all + CPUs in the system. + + Say Y only if you're working on the development of an + architecture backend for the context tracking. + + Say N otherwise, this option brings an overhead that you + don't want in production. + + +config RCU_FANOUT + int "Tree-based hierarchical RCU fanout value" + range 2 64 if 64BIT + range 2 32 if !64BIT + depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT + default 64 if 64BIT + default 32 if !64BIT + help + This option controls the fanout of hierarchical implementations + of RCU, allowing RCU to work efficiently on machines with + large numbers of CPUs. This value must be at least the fourth + root of NR_CPUS, which allows NR_CPUS to be insanely large. + The default value of RCU_FANOUT should be used for production + systems, but if you are stress-testing the RCU implementation + itself, small RCU_FANOUT values allow you to test large-system + code paths on small(er) systems. + + Select a specific number if testing RCU itself. + Take the default if unsure. + +config RCU_FANOUT_LEAF + int "Tree-based hierarchical RCU leaf-level fanout value" + range 2 64 if 64BIT + range 2 32 if !64BIT + depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT + default 16 + help + This option controls the leaf-level fanout of hierarchical + implementations of RCU, and allows trading off cache misses + against lock contention. Systems that synchronize their + scheduling-clock interrupts for energy-efficiency reasons will + want the default because the smaller leaf-level fanout keeps + lock contention levels acceptably low. Very large systems + (hundreds or thousands of CPUs) will instead want to set this + value to the maximum value possible in order to reduce the + number of cache misses incurred during RCU's grace-period + initialization. These systems tend to run CPU-bound, and thus + are not helped by synchronized interrupts, and thus tend to + skew them, which reduces lock contention enough that large + leaf-level fanouts work well. That said, setting leaf-level + fanout to a large number will likely cause problematic + lock contention on the leaf-level rcu_node structures unless + you boot with the skew_tick kernel parameter. + + Select a specific number if testing RCU itself. + + Select the maximum permissible value for large systems, but + please understand that you may also need to set the skew_tick + kernel boot parameter to avoid contention on the rcu_node + structure's locks. + + Take the default if unsure. + +config RCU_FAST_NO_HZ + bool "Accelerate last non-dyntick-idle CPU's grace periods" + depends on NO_HZ_COMMON && SMP && RCU_EXPERT + default n + help + This option permits CPUs to enter dynticks-idle state even if + they have RCU callbacks queued, and prevents RCU from waking + these CPUs up more than roughly once every four jiffies (by + default, you can adjust this using the rcutree.rcu_idle_gp_delay + parameter), thus improving energy efficiency. On the other + hand, this option increases the duration of RCU grace periods, + for example, slowing down synchronize_rcu(). + + Say Y if energy efficiency is critically important, and you + don't care about increased grace-period durations. + + Say N if you are unsure. + +config RCU_BOOST + bool "Enable RCU priority boosting" + depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT + default n + help + This option boosts the priority of preempted RCU readers that + block the current preemptible RCU grace period for too long. + This option also prevents heavy loads from blocking RCU + callback invocation for all flavors of RCU. + + Say Y here if you are working with real-time apps or heavy loads + Say N here if you are unsure. + +config RCU_BOOST_DELAY + int "Milliseconds to delay boosting after RCU grace-period start" + range 0 3000 + depends on RCU_BOOST + default 500 + help + This option specifies the time to wait after the beginning of + a given grace period before priority-boosting preempted RCU + readers blocking that grace period. Note that any RCU reader + blocking an expedited RCU grace period is boosted immediately. + + Accept the default if unsure. + +config RCU_NOCB_CPU + bool "Offload RCU callback processing from boot-selected CPUs" + depends on TREE_RCU || PREEMPT_RCU + depends on RCU_EXPERT || NO_HZ_FULL + default n + help + Use this option to reduce OS jitter for aggressive HPC or + real-time workloads. It can also be used to offload RCU + callback invocation to energy-efficient CPUs in battery-powered + asymmetric multiprocessors. + + This option offloads callback invocation from the set of + CPUs specified at boot time by the rcu_nocbs parameter. + For each such CPU, a kthread ("rcuox/N") will be created to + invoke callbacks, where the "N" is the CPU being offloaded, + and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and + "s" for RCU-sched. Nothing prevents this kthread from running + on the specified CPUs, but (1) the kthreads may be preempted + between each callback, and (2) affinity or cgroups can be used + to force the kthreads to run on whatever set of CPUs is desired. + + Say Y here if you want to help to debug reduced OS jitter. + Say N here if you are unsure. + +endmenu # "RCU Subsystem" diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug new file mode 100644 index 000000000..0ec7d1d33 --- /dev/null +++ b/kernel/rcu/Kconfig.debug @@ -0,0 +1,82 @@ +# +# RCU-related debugging configuration options +# + +menu "RCU Debugging" + +config PROVE_RCU + def_bool PROVE_LOCKING + +config TORTURE_TEST + tristate + default n + +config RCU_PERF_TEST + tristate "performance tests for RCU" + depends on DEBUG_KERNEL + select TORTURE_TEST + select SRCU + select TASKS_RCU + default n + help + This option provides a kernel module that runs performance + tests on the RCU infrastructure. The kernel module may be built + after the fact on the running kernel to be tested, if desired. + + Say Y here if you want RCU performance tests to be built into + the kernel. + Say M if you want the RCU performance tests to build as a module. + Say N if you are unsure. + +config RCU_TORTURE_TEST + tristate "torture tests for RCU" + depends on DEBUG_KERNEL + select TORTURE_TEST + select SRCU + select TASKS_RCU + default n + help + This option provides a kernel module that runs torture tests + on the RCU infrastructure. The kernel module may be built + after the fact on the running kernel to be tested, if desired. + + Say Y here if you want RCU torture tests to be built into + the kernel. + Say M if you want the RCU torture tests to build as a module. + Say N if you are unsure. + +config RCU_CPU_STALL_TIMEOUT + int "RCU CPU stall timeout in seconds" + depends on RCU_STALL_COMMON + range 3 300 + default 21 + help + If a given RCU grace period extends more than the specified + number of seconds, a CPU stall warning is printed. If the + RCU grace period persists, additional CPU stall warnings are + printed at more widely spaced intervals. + +config RCU_TRACE + bool "Enable tracing for RCU" + depends on DEBUG_KERNEL + default y if TREE_RCU + select TRACE_CLOCK + help + This option enables additional tracepoints for ftrace-style + event tracing. + + Say Y here if you want to enable RCU tracing + Say N if you are unsure. + +config RCU_EQS_DEBUG + bool "Provide debugging asserts for adding NO_HZ support to an arch" + depends on DEBUG_KERNEL + help + This option provides consistency checks in RCU's handling of + NO_HZ. These checks have proven quite helpful in detecting + bugs in arch-specific NO_HZ code. + + Say N here if you need ultimate kernel/user switch latencies + Say Y if you are unsure + +endmenu # "RCU Debugging" diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile new file mode 100644 index 000000000..020e8b6a6 --- /dev/null +++ b/kernel/rcu/Makefile @@ -0,0 +1,14 @@ +# SPDX-License-Identifier: GPL-2.0 +# Any varying coverage in these files is non-deterministic +# and is generally not a function of system call inputs. +KCOV_INSTRUMENT := n + +obj-y += update.o sync.o +obj-$(CONFIG_TREE_SRCU) += srcutree.o +obj-$(CONFIG_TINY_SRCU) += srcutiny.o +obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o +obj-$(CONFIG_RCU_PERF_TEST) += rcuperf.o +obj-$(CONFIG_TREE_RCU) += tree.o +obj-$(CONFIG_PREEMPT_RCU) += tree.o +obj-$(CONFIG_TINY_RCU) += tiny.o +obj-$(CONFIG_RCU_NEED_SEGCBLIST) += rcu_segcblist.o diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h new file mode 100644 index 000000000..4d04683c3 --- /dev/null +++ b/kernel/rcu/rcu.h @@ -0,0 +1,551 @@ +/* + * Read-Copy Update definitions shared among RCU implementations. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2011 + * + * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + +#ifndef __LINUX_RCU_H +#define __LINUX_RCU_H + +#include <trace/events/rcu.h> +#ifdef CONFIG_RCU_TRACE +#define RCU_TRACE(stmt) stmt +#else /* #ifdef CONFIG_RCU_TRACE */ +#define RCU_TRACE(stmt) +#endif /* #else #ifdef CONFIG_RCU_TRACE */ + +/* Offset to allow for unmatched rcu_irq_{enter,exit}(). */ +#define DYNTICK_IRQ_NONIDLE ((LONG_MAX / 2) + 1) + + +/* + * Grace-period counter management. + */ + +#define RCU_SEQ_CTR_SHIFT 2 +#define RCU_SEQ_STATE_MASK ((1 << RCU_SEQ_CTR_SHIFT) - 1) + +/* + * Return the counter portion of a sequence number previously returned + * by rcu_seq_snap() or rcu_seq_current(). + */ +static inline unsigned long rcu_seq_ctr(unsigned long s) +{ + return s >> RCU_SEQ_CTR_SHIFT; +} + +/* + * Return the state portion of a sequence number previously returned + * by rcu_seq_snap() or rcu_seq_current(). + */ +static inline int rcu_seq_state(unsigned long s) +{ + return s & RCU_SEQ_STATE_MASK; +} + +/* + * Set the state portion of the pointed-to sequence number. + * The caller is responsible for preventing conflicting updates. + */ +static inline void rcu_seq_set_state(unsigned long *sp, int newstate) +{ + WARN_ON_ONCE(newstate & ~RCU_SEQ_STATE_MASK); + WRITE_ONCE(*sp, (*sp & ~RCU_SEQ_STATE_MASK) + newstate); +} + +/* Adjust sequence number for start of update-side operation. */ +static inline void rcu_seq_start(unsigned long *sp) +{ + WRITE_ONCE(*sp, *sp + 1); + smp_mb(); /* Ensure update-side operation after counter increment. */ + WARN_ON_ONCE(rcu_seq_state(*sp) != 1); +} + +/* Compute the end-of-grace-period value for the specified sequence number. */ +static inline unsigned long rcu_seq_endval(unsigned long *sp) +{ + return (*sp | RCU_SEQ_STATE_MASK) + 1; +} + +/* Adjust sequence number for end of update-side operation. */ +static inline void rcu_seq_end(unsigned long *sp) +{ + smp_mb(); /* Ensure update-side operation before counter increment. */ + WARN_ON_ONCE(!rcu_seq_state(*sp)); + WRITE_ONCE(*sp, rcu_seq_endval(sp)); +} + +/* + * rcu_seq_snap - Take a snapshot of the update side's sequence number. + * + * This function returns the earliest value of the grace-period sequence number + * that will indicate that a full grace period has elapsed since the current + * time. Once the grace-period sequence number has reached this value, it will + * be safe to invoke all callbacks that have been registered prior to the + * current time. This value is the current grace-period number plus two to the + * power of the number of low-order bits reserved for state, then rounded up to + * the next value in which the state bits are all zero. + */ +static inline unsigned long rcu_seq_snap(unsigned long *sp) +{ + unsigned long s; + + s = (READ_ONCE(*sp) + 2 * RCU_SEQ_STATE_MASK + 1) & ~RCU_SEQ_STATE_MASK; + smp_mb(); /* Above access must not bleed into critical section. */ + return s; +} + +/* Return the current value the update side's sequence number, no ordering. */ +static inline unsigned long rcu_seq_current(unsigned long *sp) +{ + return READ_ONCE(*sp); +} + +/* + * Given a snapshot from rcu_seq_snap(), determine whether or not the + * corresponding update-side operation has started. + */ +static inline bool rcu_seq_started(unsigned long *sp, unsigned long s) +{ + return ULONG_CMP_LT((s - 1) & ~RCU_SEQ_STATE_MASK, READ_ONCE(*sp)); +} + +/* + * Given a snapshot from rcu_seq_snap(), determine whether or not a + * full update-side operation has occurred. + */ +static inline bool rcu_seq_done(unsigned long *sp, unsigned long s) +{ + return ULONG_CMP_GE(READ_ONCE(*sp), s); +} + +/* + * Has a grace period completed since the time the old gp_seq was collected? + */ +static inline bool rcu_seq_completed_gp(unsigned long old, unsigned long new) +{ + return ULONG_CMP_LT(old, new & ~RCU_SEQ_STATE_MASK); +} + +/* + * Has a grace period started since the time the old gp_seq was collected? + */ +static inline bool rcu_seq_new_gp(unsigned long old, unsigned long new) +{ + return ULONG_CMP_LT((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK, + new); +} + +/* + * Roughly how many full grace periods have elapsed between the collection + * of the two specified grace periods? + */ +static inline unsigned long rcu_seq_diff(unsigned long new, unsigned long old) +{ + unsigned long rnd_diff; + + if (old == new) + return 0; + /* + * Compute the number of grace periods (still shifted up), plus + * one if either of new and old is not an exact grace period. + */ + rnd_diff = (new & ~RCU_SEQ_STATE_MASK) - + ((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK) + + ((new & RCU_SEQ_STATE_MASK) || (old & RCU_SEQ_STATE_MASK)); + if (ULONG_CMP_GE(RCU_SEQ_STATE_MASK, rnd_diff)) + return 1; /* Definitely no grace period has elapsed. */ + return ((rnd_diff - RCU_SEQ_STATE_MASK - 1) >> RCU_SEQ_CTR_SHIFT) + 2; +} + +/* + * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally + * by call_rcu() and rcu callback execution, and are therefore not part of the + * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors. + */ + +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD +# define STATE_RCU_HEAD_READY 0 +# define STATE_RCU_HEAD_QUEUED 1 + +extern struct debug_obj_descr rcuhead_debug_descr; + +static inline int debug_rcu_head_queue(struct rcu_head *head) +{ + int r1; + + r1 = debug_object_activate(head, &rcuhead_debug_descr); + debug_object_active_state(head, &rcuhead_debug_descr, + STATE_RCU_HEAD_READY, + STATE_RCU_HEAD_QUEUED); + return r1; +} + +static inline void debug_rcu_head_unqueue(struct rcu_head *head) +{ + debug_object_active_state(head, &rcuhead_debug_descr, + STATE_RCU_HEAD_QUEUED, + STATE_RCU_HEAD_READY); + debug_object_deactivate(head, &rcuhead_debug_descr); +} +#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ +static inline int debug_rcu_head_queue(struct rcu_head *head) +{ + return 0; +} + +static inline void debug_rcu_head_unqueue(struct rcu_head *head) +{ +} +#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ + +void kfree(const void *); + +/* + * Reclaim the specified callback, either by invoking it (non-lazy case) + * or freeing it directly (lazy case). Return true if lazy, false otherwise. + */ +static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head) +{ + unsigned long offset = (unsigned long)head->func; + + rcu_lock_acquire(&rcu_callback_map); + if (__is_kfree_rcu_offset(offset)) { + RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);) + kfree((void *)head - offset); + rcu_lock_release(&rcu_callback_map); + return true; + } else { + RCU_TRACE(trace_rcu_invoke_callback(rn, head);) + head->func(head); + rcu_lock_release(&rcu_callback_map); + return false; + } +} + +#ifdef CONFIG_RCU_STALL_COMMON + +extern int rcu_cpu_stall_suppress; +int rcu_jiffies_till_stall_check(void); + +#define rcu_ftrace_dump_stall_suppress() \ +do { \ + if (!rcu_cpu_stall_suppress) \ + rcu_cpu_stall_suppress = 3; \ +} while (0) + +#define rcu_ftrace_dump_stall_unsuppress() \ +do { \ + if (rcu_cpu_stall_suppress == 3) \ + rcu_cpu_stall_suppress = 0; \ +} while (0) + +#else /* #endif #ifdef CONFIG_RCU_STALL_COMMON */ +#define rcu_ftrace_dump_stall_suppress() +#define rcu_ftrace_dump_stall_unsuppress() +#endif /* #ifdef CONFIG_RCU_STALL_COMMON */ + +/* + * Strings used in tracepoints need to be exported via the + * tracing system such that tools like perf and trace-cmd can + * translate the string address pointers to actual text. + */ +#define TPS(x) tracepoint_string(x) + +/* + * Dump the ftrace buffer, but only one time per callsite per boot. + */ +#define rcu_ftrace_dump(oops_dump_mode) \ +do { \ + static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \ + \ + if (!atomic_read(&___rfd_beenhere) && \ + !atomic_xchg(&___rfd_beenhere, 1)) { \ + tracing_off(); \ + rcu_ftrace_dump_stall_suppress(); \ + ftrace_dump(oops_dump_mode); \ + rcu_ftrace_dump_stall_unsuppress(); \ + } \ +} while (0) + +void rcu_early_boot_tests(void); +void rcu_test_sync_prims(void); + +/* + * This function really isn't for public consumption, but RCU is special in + * that context switches can allow the state machine to make progress. + */ +extern void resched_cpu(int cpu); + +#if defined(SRCU) || !defined(TINY_RCU) + +#include <linux/rcu_node_tree.h> + +extern int rcu_num_lvls; +extern int num_rcu_lvl[]; +extern int rcu_num_nodes; +static bool rcu_fanout_exact; +static int rcu_fanout_leaf; + +/* + * Compute the per-level fanout, either using the exact fanout specified + * or balancing the tree, depending on the rcu_fanout_exact boot parameter. + */ +static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) +{ + int i; + + if (rcu_fanout_exact) { + levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf; + for (i = rcu_num_lvls - 2; i >= 0; i--) + levelspread[i] = RCU_FANOUT; + } else { + int ccur; + int cprv; + + cprv = nr_cpu_ids; + for (i = rcu_num_lvls - 1; i >= 0; i--) { + ccur = levelcnt[i]; + levelspread[i] = (cprv + ccur - 1) / ccur; + cprv = ccur; + } + } +} + +/* Returns first leaf rcu_node of the specified RCU flavor. */ +#define rcu_first_leaf_node(rsp) ((rsp)->level[rcu_num_lvls - 1]) + +/* Is this rcu_node a leaf? */ +#define rcu_is_leaf_node(rnp) ((rnp)->level == rcu_num_lvls - 1) + +/* Is this rcu_node the last leaf? */ +#define rcu_is_last_leaf_node(rsp, rnp) ((rnp) == &(rsp)->node[rcu_num_nodes - 1]) + +/* + * Do a full breadth-first scan of the rcu_node structures for the + * specified rcu_state structure. + */ +#define rcu_for_each_node_breadth_first(rsp, rnp) \ + for ((rnp) = &(rsp)->node[0]; \ + (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) + +/* + * Do a breadth-first scan of the non-leaf rcu_node structures for the + * specified rcu_state structure. Note that if there is a singleton + * rcu_node tree with but one rcu_node structure, this loop is a no-op. + */ +#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \ + for ((rnp) = &(rsp)->node[0]; !rcu_is_leaf_node(rsp, rnp); (rnp)++) + +/* + * Scan the leaves of the rcu_node hierarchy for the specified rcu_state + * structure. Note that if there is a singleton rcu_node tree with but + * one rcu_node structure, this loop -will- visit the rcu_node structure. + * It is still a leaf node, even if it is also the root node. + */ +#define rcu_for_each_leaf_node(rsp, rnp) \ + for ((rnp) = rcu_first_leaf_node(rsp); \ + (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) + +/* + * Iterate over all possible CPUs in a leaf RCU node. + */ +#define for_each_leaf_node_possible_cpu(rnp, cpu) \ + for ((cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \ + (cpu) <= rnp->grphi; \ + (cpu) = cpumask_next((cpu), cpu_possible_mask)) + +/* + * Iterate over all CPUs in a leaf RCU node's specified mask. + */ +#define rcu_find_next_bit(rnp, cpu, mask) \ + ((rnp)->grplo + find_next_bit(&(mask), BITS_PER_LONG, (cpu))) +#define for_each_leaf_node_cpu_mask(rnp, cpu, mask) \ + for ((cpu) = rcu_find_next_bit((rnp), 0, (mask)); \ + (cpu) <= rnp->grphi; \ + (cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask))) + +/* + * Wrappers for the rcu_node::lock acquire and release. + * + * Because the rcu_nodes form a tree, the tree traversal locking will observe + * different lock values, this in turn means that an UNLOCK of one level + * followed by a LOCK of another level does not imply a full memory barrier; + * and most importantly transitivity is lost. + * + * In order to restore full ordering between tree levels, augment the regular + * lock acquire functions with smp_mb__after_unlock_lock(). + * + * As ->lock of struct rcu_node is a __private field, therefore one should use + * these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock. + */ +#define raw_spin_lock_rcu_node(p) \ +do { \ + raw_spin_lock(&ACCESS_PRIVATE(p, lock)); \ + smp_mb__after_unlock_lock(); \ +} while (0) + +#define raw_spin_unlock_rcu_node(p) raw_spin_unlock(&ACCESS_PRIVATE(p, lock)) + +#define raw_spin_lock_irq_rcu_node(p) \ +do { \ + raw_spin_lock_irq(&ACCESS_PRIVATE(p, lock)); \ + smp_mb__after_unlock_lock(); \ +} while (0) + +#define raw_spin_unlock_irq_rcu_node(p) \ + raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock)) + +#define raw_spin_lock_irqsave_rcu_node(p, flags) \ +do { \ + raw_spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \ + smp_mb__after_unlock_lock(); \ +} while (0) + +#define raw_spin_unlock_irqrestore_rcu_node(p, flags) \ + raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags) + +#define raw_spin_trylock_rcu_node(p) \ +({ \ + bool ___locked = raw_spin_trylock(&ACCESS_PRIVATE(p, lock)); \ + \ + if (___locked) \ + smp_mb__after_unlock_lock(); \ + ___locked; \ +}) + +#define raw_lockdep_assert_held_rcu_node(p) \ + lockdep_assert_held(&ACCESS_PRIVATE(p, lock)) + +#endif /* #if defined(SRCU) || !defined(TINY_RCU) */ + +#ifdef CONFIG_TINY_RCU +/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */ +static inline bool rcu_gp_is_normal(void) { return true; } +static inline bool rcu_gp_is_expedited(void) { return false; } +static inline void rcu_expedite_gp(void) { } +static inline void rcu_unexpedite_gp(void) { } +static inline void rcu_request_urgent_qs_task(struct task_struct *t) { } +#else /* #ifdef CONFIG_TINY_RCU */ +bool rcu_gp_is_normal(void); /* Internal RCU use. */ +bool rcu_gp_is_expedited(void); /* Internal RCU use. */ +void rcu_expedite_gp(void); +void rcu_unexpedite_gp(void); +void rcupdate_announce_bootup_oddness(void); +void rcu_request_urgent_qs_task(struct task_struct *t); +#endif /* #else #ifdef CONFIG_TINY_RCU */ + +#define RCU_SCHEDULER_INACTIVE 0 +#define RCU_SCHEDULER_INIT 1 +#define RCU_SCHEDULER_RUNNING 2 + +enum rcutorture_type { + RCU_FLAVOR, + RCU_BH_FLAVOR, + RCU_SCHED_FLAVOR, + RCU_TASKS_FLAVOR, + SRCU_FLAVOR, + INVALID_RCU_FLAVOR +}; + +#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) +void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, + unsigned long *gp_seq); +void rcutorture_record_progress(unsigned long vernum); +void do_trace_rcu_torture_read(const char *rcutorturename, + struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, + unsigned long c); +#else +static inline void rcutorture_get_gp_data(enum rcutorture_type test_type, + int *flags, unsigned long *gp_seq) +{ + *flags = 0; + *gp_seq = 0; +} +static inline void rcutorture_record_progress(unsigned long vernum) { } +#ifdef CONFIG_RCU_TRACE +void do_trace_rcu_torture_read(const char *rcutorturename, + struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, + unsigned long c); +#else +#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ + do { } while (0) +#endif +#endif + +#ifdef CONFIG_TINY_SRCU + +static inline void srcutorture_get_gp_data(enum rcutorture_type test_type, + struct srcu_struct *sp, int *flags, + unsigned long *gp_seq) +{ + if (test_type != SRCU_FLAVOR) + return; + *flags = 0; + *gp_seq = sp->srcu_idx; +} + +#elif defined(CONFIG_TREE_SRCU) + +void srcutorture_get_gp_data(enum rcutorture_type test_type, + struct srcu_struct *sp, int *flags, + unsigned long *gp_seq); + +#endif + +#ifdef CONFIG_TINY_RCU +static inline unsigned long rcu_get_gp_seq(void) { return 0; } +static inline unsigned long rcu_bh_get_gp_seq(void) { return 0; } +static inline unsigned long rcu_sched_get_gp_seq(void) { return 0; } +static inline unsigned long rcu_exp_batches_completed(void) { return 0; } +static inline unsigned long rcu_exp_batches_completed_sched(void) { return 0; } +static inline unsigned long +srcu_batches_completed(struct srcu_struct *sp) { return 0; } +static inline void rcu_force_quiescent_state(void) { } +static inline void rcu_bh_force_quiescent_state(void) { } +static inline void rcu_sched_force_quiescent_state(void) { } +static inline void show_rcu_gp_kthreads(void) { } +static inline int rcu_get_gp_kthreads_prio(void) { return 0; } +#else /* #ifdef CONFIG_TINY_RCU */ +unsigned long rcu_get_gp_seq(void); +unsigned long rcu_bh_get_gp_seq(void); +unsigned long rcu_sched_get_gp_seq(void); +unsigned long rcu_exp_batches_completed(void); +unsigned long rcu_exp_batches_completed_sched(void); +unsigned long srcu_batches_completed(struct srcu_struct *sp); +void show_rcu_gp_kthreads(void); +int rcu_get_gp_kthreads_prio(void); +void rcu_force_quiescent_state(void); +void rcu_bh_force_quiescent_state(void); +void rcu_sched_force_quiescent_state(void); +extern struct workqueue_struct *rcu_gp_wq; +extern struct workqueue_struct *rcu_par_gp_wq; +#endif /* #else #ifdef CONFIG_TINY_RCU */ + +#ifdef CONFIG_RCU_NOCB_CPU +bool rcu_is_nocb_cpu(int cpu); +#else +static inline bool rcu_is_nocb_cpu(int cpu) { return false; } +#endif + +#endif /* __LINUX_RCU_H */ diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c new file mode 100644 index 000000000..5aff271ad --- /dev/null +++ b/kernel/rcu/rcu_segcblist.c @@ -0,0 +1,428 @@ +/* + * RCU segmented callback lists, function definitions + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2017 + * + * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/interrupt.h> +#include <linux/rcupdate.h> + +#include "rcu_segcblist.h" + +/* Initialize simple callback list. */ +void rcu_cblist_init(struct rcu_cblist *rclp) +{ + rclp->head = NULL; + rclp->tail = &rclp->head; + rclp->len = 0; + rclp->len_lazy = 0; +} + +/* + * Dequeue the oldest rcu_head structure from the specified callback + * list. This function assumes that the callback is non-lazy, but + * the caller can later invoke rcu_cblist_dequeued_lazy() if it + * finds otherwise (and if it cares about laziness). This allows + * different users to have different ways of determining laziness. + */ +struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp) +{ + struct rcu_head *rhp; + + rhp = rclp->head; + if (!rhp) + return NULL; + rclp->len--; + rclp->head = rhp->next; + if (!rclp->head) + rclp->tail = &rclp->head; + return rhp; +} + +/* + * Initialize an rcu_segcblist structure. + */ +void rcu_segcblist_init(struct rcu_segcblist *rsclp) +{ + int i; + + BUILD_BUG_ON(RCU_NEXT_TAIL + 1 != ARRAY_SIZE(rsclp->gp_seq)); + BUILD_BUG_ON(ARRAY_SIZE(rsclp->tails) != ARRAY_SIZE(rsclp->gp_seq)); + rsclp->head = NULL; + for (i = 0; i < RCU_CBLIST_NSEGS; i++) + rsclp->tails[i] = &rsclp->head; + rsclp->len = 0; + rsclp->len_lazy = 0; +} + +/* + * Disable the specified rcu_segcblist structure, so that callbacks can + * no longer be posted to it. This structure must be empty. + */ +void rcu_segcblist_disable(struct rcu_segcblist *rsclp) +{ + WARN_ON_ONCE(!rcu_segcblist_empty(rsclp)); + WARN_ON_ONCE(rcu_segcblist_n_cbs(rsclp)); + WARN_ON_ONCE(rcu_segcblist_n_lazy_cbs(rsclp)); + rsclp->tails[RCU_NEXT_TAIL] = NULL; +} + +/* + * Does the specified rcu_segcblist structure contain callbacks that + * are ready to be invoked? + */ +bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp) +{ + return rcu_segcblist_is_enabled(rsclp) && + &rsclp->head != rsclp->tails[RCU_DONE_TAIL]; +} + +/* + * Does the specified rcu_segcblist structure contain callbacks that + * are still pending, that is, not yet ready to be invoked? + */ +bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp) +{ + return rcu_segcblist_is_enabled(rsclp) && + !rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL); +} + +/* + * Return a pointer to the first callback in the specified rcu_segcblist + * structure. This is useful for diagnostics. + */ +struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp) +{ + if (rcu_segcblist_is_enabled(rsclp)) + return rsclp->head; + return NULL; +} + +/* + * Return a pointer to the first pending callback in the specified + * rcu_segcblist structure. This is useful just after posting a given + * callback -- if that callback is the first pending callback, then + * you cannot rely on someone else having already started up the required + * grace period. + */ +struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp) +{ + if (rcu_segcblist_is_enabled(rsclp)) + return *rsclp->tails[RCU_DONE_TAIL]; + return NULL; +} + +/* + * Enqueue the specified callback onto the specified rcu_segcblist + * structure, updating accounting as needed. Note that the ->len + * field may be accessed locklessly, hence the WRITE_ONCE(). + * The ->len field is used by rcu_barrier() and friends to determine + * if it must post a callback on this structure, and it is OK + * for rcu_barrier() to sometimes post callbacks needlessly, but + * absolutely not OK for it to ever miss posting a callback. + */ +void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp, + struct rcu_head *rhp, bool lazy) +{ + WRITE_ONCE(rsclp->len, rsclp->len + 1); /* ->len sampled locklessly. */ + if (lazy) + rsclp->len_lazy++; + smp_mb(); /* Ensure counts are updated before callback is enqueued. */ + rhp->next = NULL; + *rsclp->tails[RCU_NEXT_TAIL] = rhp; + rsclp->tails[RCU_NEXT_TAIL] = &rhp->next; +} + +/* + * Entrain the specified callback onto the specified rcu_segcblist at + * the end of the last non-empty segment. If the entire rcu_segcblist + * is empty, make no change, but return false. + * + * This is intended for use by rcu_barrier()-like primitives, -not- + * for normal grace-period use. IMPORTANT: The callback you enqueue + * will wait for all prior callbacks, NOT necessarily for a grace + * period. You have been warned. + */ +bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp, + struct rcu_head *rhp, bool lazy) +{ + int i; + + if (rcu_segcblist_n_cbs(rsclp) == 0) + return false; + WRITE_ONCE(rsclp->len, rsclp->len + 1); + if (lazy) + rsclp->len_lazy++; + smp_mb(); /* Ensure counts are updated before callback is entrained. */ + rhp->next = NULL; + for (i = RCU_NEXT_TAIL; i > RCU_DONE_TAIL; i--) + if (rsclp->tails[i] != rsclp->tails[i - 1]) + break; + *rsclp->tails[i] = rhp; + for (; i <= RCU_NEXT_TAIL; i++) + rsclp->tails[i] = &rhp->next; + return true; +} + +/* + * Extract only the counts from the specified rcu_segcblist structure, + * and place them in the specified rcu_cblist structure. This function + * supports both callback orphaning and invocation, hence the separation + * of counts and callbacks. (Callbacks ready for invocation must be + * orphaned and adopted separately from pending callbacks, but counts + * apply to all callbacks. Locking must be used to make sure that + * both orphaned-callbacks lists are consistent.) + */ +void rcu_segcblist_extract_count(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp) +{ + rclp->len_lazy += rsclp->len_lazy; + rclp->len += rsclp->len; + rsclp->len_lazy = 0; + WRITE_ONCE(rsclp->len, 0); /* ->len sampled locklessly. */ +} + +/* + * Extract only those callbacks ready to be invoked from the specified + * rcu_segcblist structure and place them in the specified rcu_cblist + * structure. + */ +void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp) +{ + int i; + + if (!rcu_segcblist_ready_cbs(rsclp)) + return; /* Nothing to do. */ + *rclp->tail = rsclp->head; + rsclp->head = *rsclp->tails[RCU_DONE_TAIL]; + *rsclp->tails[RCU_DONE_TAIL] = NULL; + rclp->tail = rsclp->tails[RCU_DONE_TAIL]; + for (i = RCU_CBLIST_NSEGS - 1; i >= RCU_DONE_TAIL; i--) + if (rsclp->tails[i] == rsclp->tails[RCU_DONE_TAIL]) + rsclp->tails[i] = &rsclp->head; +} + +/* + * Extract only those callbacks still pending (not yet ready to be + * invoked) from the specified rcu_segcblist structure and place them in + * the specified rcu_cblist structure. Note that this loses information + * about any callbacks that might have been partway done waiting for + * their grace period. Too bad! They will have to start over. + */ +void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp) +{ + int i; + + if (!rcu_segcblist_pend_cbs(rsclp)) + return; /* Nothing to do. */ + *rclp->tail = *rsclp->tails[RCU_DONE_TAIL]; + rclp->tail = rsclp->tails[RCU_NEXT_TAIL]; + *rsclp->tails[RCU_DONE_TAIL] = NULL; + for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++) + rsclp->tails[i] = rsclp->tails[RCU_DONE_TAIL]; +} + +/* + * Insert counts from the specified rcu_cblist structure in the + * specified rcu_segcblist structure. + */ +void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp) +{ + rsclp->len_lazy += rclp->len_lazy; + /* ->len sampled locklessly. */ + WRITE_ONCE(rsclp->len, rsclp->len + rclp->len); + rclp->len_lazy = 0; + rclp->len = 0; +} + +/* + * Move callbacks from the specified rcu_cblist to the beginning of the + * done-callbacks segment of the specified rcu_segcblist. + */ +void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp) +{ + int i; + + if (!rclp->head) + return; /* No callbacks to move. */ + *rclp->tail = rsclp->head; + rsclp->head = rclp->head; + for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++) + if (&rsclp->head == rsclp->tails[i]) + rsclp->tails[i] = rclp->tail; + else + break; + rclp->head = NULL; + rclp->tail = &rclp->head; +} + +/* + * Move callbacks from the specified rcu_cblist to the end of the + * new-callbacks segment of the specified rcu_segcblist. + */ +void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp) +{ + if (!rclp->head) + return; /* Nothing to do. */ + *rsclp->tails[RCU_NEXT_TAIL] = rclp->head; + rsclp->tails[RCU_NEXT_TAIL] = rclp->tail; + rclp->head = NULL; + rclp->tail = &rclp->head; +} + +/* + * Advance the callbacks in the specified rcu_segcblist structure based + * on the current value passed in for the grace-period counter. + */ +void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq) +{ + int i, j; + + WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp)); + if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL)) + return; + + /* + * Find all callbacks whose ->gp_seq numbers indicate that they + * are ready to invoke, and put them into the RCU_DONE_TAIL segment. + */ + for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) { + if (ULONG_CMP_LT(seq, rsclp->gp_seq[i])) + break; + rsclp->tails[RCU_DONE_TAIL] = rsclp->tails[i]; + } + + /* If no callbacks moved, nothing more need be done. */ + if (i == RCU_WAIT_TAIL) + return; + + /* Clean up tail pointers that might have been misordered above. */ + for (j = RCU_WAIT_TAIL; j < i; j++) + rsclp->tails[j] = rsclp->tails[RCU_DONE_TAIL]; + + /* + * Callbacks moved, so clean up the misordered ->tails[] pointers + * that now point into the middle of the list of ready-to-invoke + * callbacks. The overall effect is to copy down the later pointers + * into the gap that was created by the now-ready segments. + */ + for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) { + if (rsclp->tails[j] == rsclp->tails[RCU_NEXT_TAIL]) + break; /* No more callbacks. */ + rsclp->tails[j] = rsclp->tails[i]; + rsclp->gp_seq[j] = rsclp->gp_seq[i]; + } +} + +/* + * "Accelerate" callbacks based on more-accurate grace-period information. + * The reason for this is that RCU does not synchronize the beginnings and + * ends of grace periods, and that callbacks are posted locally. This in + * turn means that the callbacks must be labelled conservatively early + * on, as getting exact information would degrade both performance and + * scalability. When more accurate grace-period information becomes + * available, previously posted callbacks can be "accelerated", marking + * them to complete at the end of the earlier grace period. + * + * This function operates on an rcu_segcblist structure, and also the + * grace-period sequence number seq at which new callbacks would become + * ready to invoke. Returns true if there are callbacks that won't be + * ready to invoke until seq, false otherwise. + */ +bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq) +{ + int i; + + WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp)); + if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL)) + return false; + + /* + * Find the segment preceding the oldest segment of callbacks + * whose ->gp_seq[] completion is at or after that passed in via + * "seq", skipping any empty segments. This oldest segment, along + * with any later segments, can be merged in with any newly arrived + * callbacks in the RCU_NEXT_TAIL segment, and assigned "seq" + * as their ->gp_seq[] grace-period completion sequence number. + */ + for (i = RCU_NEXT_READY_TAIL; i > RCU_DONE_TAIL; i--) + if (rsclp->tails[i] != rsclp->tails[i - 1] && + ULONG_CMP_LT(rsclp->gp_seq[i], seq)) + break; + + /* + * If all the segments contain callbacks that correspond to + * earlier grace-period sequence numbers than "seq", leave. + * Assuming that the rcu_segcblist structure has enough + * segments in its arrays, this can only happen if some of + * the non-done segments contain callbacks that really are + * ready to invoke. This situation will get straightened + * out by the next call to rcu_segcblist_advance(). + * + * Also advance to the oldest segment of callbacks whose + * ->gp_seq[] completion is at or after that passed in via "seq", + * skipping any empty segments. + */ + if (++i >= RCU_NEXT_TAIL) + return false; + + /* + * Merge all later callbacks, including newly arrived callbacks, + * into the segment located by the for-loop above. Assign "seq" + * as the ->gp_seq[] value in order to correctly handle the case + * where there were no pending callbacks in the rcu_segcblist + * structure other than in the RCU_NEXT_TAIL segment. + */ + for (; i < RCU_NEXT_TAIL; i++) { + rsclp->tails[i] = rsclp->tails[RCU_NEXT_TAIL]; + rsclp->gp_seq[i] = seq; + } + return true; +} + +/* + * Merge the source rcu_segcblist structure into the destination + * rcu_segcblist structure, then initialize the source. Any pending + * callbacks from the source get to start over. It is best to + * advance and accelerate both the destination and the source + * before merging. + */ +void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp, + struct rcu_segcblist *src_rsclp) +{ + struct rcu_cblist donecbs; + struct rcu_cblist pendcbs; + + rcu_cblist_init(&donecbs); + rcu_cblist_init(&pendcbs); + rcu_segcblist_extract_count(src_rsclp, &donecbs); + rcu_segcblist_extract_done_cbs(src_rsclp, &donecbs); + rcu_segcblist_extract_pend_cbs(src_rsclp, &pendcbs); + rcu_segcblist_insert_count(dst_rsclp, &donecbs); + rcu_segcblist_insert_done_cbs(dst_rsclp, &donecbs); + rcu_segcblist_insert_pend_cbs(dst_rsclp, &pendcbs); + rcu_segcblist_init(src_rsclp); +} diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h new file mode 100644 index 000000000..948470cef --- /dev/null +++ b/kernel/rcu/rcu_segcblist.h @@ -0,0 +1,138 @@ +/* + * RCU segmented callback lists, internal-to-rcu header file + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2017 + * + * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + +#include <linux/rcu_segcblist.h> + +/* + * Account for the fact that a previously dequeued callback turned out + * to be marked as lazy. + */ +static inline void rcu_cblist_dequeued_lazy(struct rcu_cblist *rclp) +{ + rclp->len_lazy--; +} + +void rcu_cblist_init(struct rcu_cblist *rclp); +struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp); + +/* + * Is the specified rcu_segcblist structure empty? + * + * But careful! The fact that the ->head field is NULL does not + * necessarily imply that there are no callbacks associated with + * this structure. When callbacks are being invoked, they are + * removed as a group. If callback invocation must be preempted, + * the remaining callbacks will be added back to the list. Either + * way, the counts are updated later. + * + * So it is often the case that rcu_segcblist_n_cbs() should be used + * instead. + */ +static inline bool rcu_segcblist_empty(struct rcu_segcblist *rsclp) +{ + return !rsclp->head; +} + +/* Return number of callbacks in segmented callback list. */ +static inline long rcu_segcblist_n_cbs(struct rcu_segcblist *rsclp) +{ + return READ_ONCE(rsclp->len); +} + +/* Return number of lazy callbacks in segmented callback list. */ +static inline long rcu_segcblist_n_lazy_cbs(struct rcu_segcblist *rsclp) +{ + return rsclp->len_lazy; +} + +/* Return number of lazy callbacks in segmented callback list. */ +static inline long rcu_segcblist_n_nonlazy_cbs(struct rcu_segcblist *rsclp) +{ + return rsclp->len - rsclp->len_lazy; +} + +/* + * Is the specified rcu_segcblist enabled, for example, not corresponding + * to an offline or callback-offloaded CPU? + */ +static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp) +{ + return !!rsclp->tails[RCU_NEXT_TAIL]; +} + +/* + * Are all segments following the specified segment of the specified + * rcu_segcblist structure empty of callbacks? (The specified + * segment might well contain callbacks.) + */ +static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg) +{ + return !*rsclp->tails[seg]; +} + +/* + * Interim function to return rcu_segcblist head pointer. Longer term, the + * rcu_segcblist will be used more pervasively, removing the need for this + * function. + */ +static inline struct rcu_head *rcu_segcblist_head(struct rcu_segcblist *rsclp) +{ + return rsclp->head; +} + +/* + * Interim function to return rcu_segcblist head pointer. Longer term, the + * rcu_segcblist will be used more pervasively, removing the need for this + * function. + */ +static inline struct rcu_head **rcu_segcblist_tail(struct rcu_segcblist *rsclp) +{ + WARN_ON_ONCE(rcu_segcblist_empty(rsclp)); + return rsclp->tails[RCU_NEXT_TAIL]; +} + +void rcu_segcblist_init(struct rcu_segcblist *rsclp); +void rcu_segcblist_disable(struct rcu_segcblist *rsclp); +bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp); +bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp); +struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp); +struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp); +void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp, + struct rcu_head *rhp, bool lazy); +bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp, + struct rcu_head *rhp, bool lazy); +void rcu_segcblist_extract_count(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp); +void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp); +void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp); +void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp); +void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp); +void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp, + struct rcu_cblist *rclp); +void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq); +bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq); +void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp, + struct rcu_segcblist *src_rsclp); diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c new file mode 100644 index 000000000..19249b86f --- /dev/null +++ b/kernel/rcu/rcuperf.c @@ -0,0 +1,761 @@ +/* + * Read-Copy Update module-based performance-test facility + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright (C) IBM Corporation, 2015 + * + * Authors: Paul E. McKenney <paulmck@us.ibm.com> + */ + +#define pr_fmt(fmt) fmt + +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/module.h> +#include <linux/kthread.h> +#include <linux/err.h> +#include <linux/spinlock.h> +#include <linux/smp.h> +#include <linux/rcupdate.h> +#include <linux/interrupt.h> +#include <linux/sched.h> +#include <uapi/linux/sched/types.h> +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/completion.h> +#include <linux/moduleparam.h> +#include <linux/percpu.h> +#include <linux/notifier.h> +#include <linux/reboot.h> +#include <linux/freezer.h> +#include <linux/cpu.h> +#include <linux/delay.h> +#include <linux/stat.h> +#include <linux/srcu.h> +#include <linux/slab.h> +#include <asm/byteorder.h> +#include <linux/torture.h> +#include <linux/vmalloc.h> + +#include "rcu.h" + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>"); + +#define PERF_FLAG "-perf:" +#define PERFOUT_STRING(s) \ + pr_alert("%s" PERF_FLAG " %s\n", perf_type, s) +#define VERBOSE_PERFOUT_STRING(s) \ + do { if (verbose) pr_alert("%s" PERF_FLAG " %s\n", perf_type, s); } while (0) +#define VERBOSE_PERFOUT_ERRSTRING(s) \ + do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0) + +/* + * The intended use cases for the nreaders and nwriters module parameters + * are as follows: + * + * 1. Specify only the nr_cpus kernel boot parameter. This will + * set both nreaders and nwriters to the value specified by + * nr_cpus for a mixed reader/writer test. + * + * 2. Specify the nr_cpus kernel boot parameter, but set + * rcuperf.nreaders to zero. This will set nwriters to the + * value specified by nr_cpus for an update-only test. + * + * 3. Specify the nr_cpus kernel boot parameter, but set + * rcuperf.nwriters to zero. This will set nreaders to the + * value specified by nr_cpus for a read-only test. + * + * Various other use cases may of course be specified. + */ + +torture_param(bool, gp_async, false, "Use asynchronous GP wait primitives"); +torture_param(int, gp_async_max, 1000, "Max # outstanding waits per reader"); +torture_param(bool, gp_exp, false, "Use expedited GP wait primitives"); +torture_param(int, holdoff, 10, "Holdoff time before test start (s)"); +torture_param(int, nreaders, -1, "Number of RCU reader threads"); +torture_param(int, nwriters, -1, "Number of RCU updater threads"); +torture_param(bool, shutdown, !IS_ENABLED(MODULE), + "Shutdown at end of performance tests."); +torture_param(int, verbose, 1, "Enable verbose debugging printk()s"); +torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable"); + +static char *perf_type = "rcu"; +module_param(perf_type, charp, 0444); +MODULE_PARM_DESC(perf_type, "Type of RCU to performance-test (rcu, rcu_bh, ...)"); + +static int nrealreaders; +static int nrealwriters; +static struct task_struct **writer_tasks; +static struct task_struct **reader_tasks; +static struct task_struct *shutdown_task; + +static u64 **writer_durations; +static int *writer_n_durations; +static atomic_t n_rcu_perf_reader_started; +static atomic_t n_rcu_perf_writer_started; +static atomic_t n_rcu_perf_writer_finished; +static wait_queue_head_t shutdown_wq; +static u64 t_rcu_perf_writer_started; +static u64 t_rcu_perf_writer_finished; +static unsigned long b_rcu_perf_writer_started; +static unsigned long b_rcu_perf_writer_finished; +static DEFINE_PER_CPU(atomic_t, n_async_inflight); + +static int rcu_perf_writer_state; +#define RTWS_INIT 0 +#define RTWS_ASYNC 1 +#define RTWS_BARRIER 2 +#define RTWS_EXP_SYNC 3 +#define RTWS_SYNC 4 +#define RTWS_IDLE 5 +#define RTWS_STOPPING 6 + +#define MAX_MEAS 10000 +#define MIN_MEAS 100 + +/* + * Operations vector for selecting different types of tests. + */ + +struct rcu_perf_ops { + int ptype; + void (*init)(void); + void (*cleanup)(void); + int (*readlock)(void); + void (*readunlock)(int idx); + unsigned long (*get_gp_seq)(void); + unsigned long (*gp_diff)(unsigned long new, unsigned long old); + unsigned long (*exp_completed)(void); + void (*async)(struct rcu_head *head, rcu_callback_t func); + void (*gp_barrier)(void); + void (*sync)(void); + void (*exp_sync)(void); + const char *name; +}; + +static struct rcu_perf_ops *cur_ops; + +/* + * Definitions for rcu perf testing. + */ + +static int rcu_perf_read_lock(void) __acquires(RCU) +{ + rcu_read_lock(); + return 0; +} + +static void rcu_perf_read_unlock(int idx) __releases(RCU) +{ + rcu_read_unlock(); +} + +static unsigned long __maybe_unused rcu_no_completed(void) +{ + return 0; +} + +static void rcu_sync_perf_init(void) +{ +} + +static struct rcu_perf_ops rcu_ops = { + .ptype = RCU_FLAVOR, + .init = rcu_sync_perf_init, + .readlock = rcu_perf_read_lock, + .readunlock = rcu_perf_read_unlock, + .get_gp_seq = rcu_get_gp_seq, + .gp_diff = rcu_seq_diff, + .exp_completed = rcu_exp_batches_completed, + .async = call_rcu, + .gp_barrier = rcu_barrier, + .sync = synchronize_rcu, + .exp_sync = synchronize_rcu_expedited, + .name = "rcu" +}; + +/* + * Definitions for rcu_bh perf testing. + */ + +static int rcu_bh_perf_read_lock(void) __acquires(RCU_BH) +{ + rcu_read_lock_bh(); + return 0; +} + +static void rcu_bh_perf_read_unlock(int idx) __releases(RCU_BH) +{ + rcu_read_unlock_bh(); +} + +static struct rcu_perf_ops rcu_bh_ops = { + .ptype = RCU_BH_FLAVOR, + .init = rcu_sync_perf_init, + .readlock = rcu_bh_perf_read_lock, + .readunlock = rcu_bh_perf_read_unlock, + .get_gp_seq = rcu_bh_get_gp_seq, + .gp_diff = rcu_seq_diff, + .exp_completed = rcu_exp_batches_completed_sched, + .async = call_rcu_bh, + .gp_barrier = rcu_barrier_bh, + .sync = synchronize_rcu_bh, + .exp_sync = synchronize_rcu_bh_expedited, + .name = "rcu_bh" +}; + +/* + * Definitions for srcu perf testing. + */ + +DEFINE_STATIC_SRCU(srcu_ctl_perf); +static struct srcu_struct *srcu_ctlp = &srcu_ctl_perf; + +static int srcu_perf_read_lock(void) __acquires(srcu_ctlp) +{ + return srcu_read_lock(srcu_ctlp); +} + +static void srcu_perf_read_unlock(int idx) __releases(srcu_ctlp) +{ + srcu_read_unlock(srcu_ctlp, idx); +} + +static unsigned long srcu_perf_completed(void) +{ + return srcu_batches_completed(srcu_ctlp); +} + +static void srcu_call_rcu(struct rcu_head *head, rcu_callback_t func) +{ + call_srcu(srcu_ctlp, head, func); +} + +static void srcu_rcu_barrier(void) +{ + srcu_barrier(srcu_ctlp); +} + +static void srcu_perf_synchronize(void) +{ + synchronize_srcu(srcu_ctlp); +} + +static void srcu_perf_synchronize_expedited(void) +{ + synchronize_srcu_expedited(srcu_ctlp); +} + +static struct rcu_perf_ops srcu_ops = { + .ptype = SRCU_FLAVOR, + .init = rcu_sync_perf_init, + .readlock = srcu_perf_read_lock, + .readunlock = srcu_perf_read_unlock, + .get_gp_seq = srcu_perf_completed, + .gp_diff = rcu_seq_diff, + .exp_completed = srcu_perf_completed, + .async = srcu_call_rcu, + .gp_barrier = srcu_rcu_barrier, + .sync = srcu_perf_synchronize, + .exp_sync = srcu_perf_synchronize_expedited, + .name = "srcu" +}; + +static struct srcu_struct srcud; + +static void srcu_sync_perf_init(void) +{ + srcu_ctlp = &srcud; + init_srcu_struct(srcu_ctlp); +} + +static void srcu_sync_perf_cleanup(void) +{ + cleanup_srcu_struct(srcu_ctlp); +} + +static struct rcu_perf_ops srcud_ops = { + .ptype = SRCU_FLAVOR, + .init = srcu_sync_perf_init, + .cleanup = srcu_sync_perf_cleanup, + .readlock = srcu_perf_read_lock, + .readunlock = srcu_perf_read_unlock, + .get_gp_seq = srcu_perf_completed, + .gp_diff = rcu_seq_diff, + .exp_completed = srcu_perf_completed, + .async = srcu_call_rcu, + .gp_barrier = srcu_rcu_barrier, + .sync = srcu_perf_synchronize, + .exp_sync = srcu_perf_synchronize_expedited, + .name = "srcud" +}; + +/* + * Definitions for sched perf testing. + */ + +static int sched_perf_read_lock(void) +{ + preempt_disable(); + return 0; +} + +static void sched_perf_read_unlock(int idx) +{ + preempt_enable(); +} + +static struct rcu_perf_ops sched_ops = { + .ptype = RCU_SCHED_FLAVOR, + .init = rcu_sync_perf_init, + .readlock = sched_perf_read_lock, + .readunlock = sched_perf_read_unlock, + .get_gp_seq = rcu_sched_get_gp_seq, + .gp_diff = rcu_seq_diff, + .exp_completed = rcu_exp_batches_completed_sched, + .async = call_rcu_sched, + .gp_barrier = rcu_barrier_sched, + .sync = synchronize_sched, + .exp_sync = synchronize_sched_expedited, + .name = "sched" +}; + +/* + * Definitions for RCU-tasks perf testing. + */ + +static int tasks_perf_read_lock(void) +{ + return 0; +} + +static void tasks_perf_read_unlock(int idx) +{ +} + +static struct rcu_perf_ops tasks_ops = { + .ptype = RCU_TASKS_FLAVOR, + .init = rcu_sync_perf_init, + .readlock = tasks_perf_read_lock, + .readunlock = tasks_perf_read_unlock, + .get_gp_seq = rcu_no_completed, + .gp_diff = rcu_seq_diff, + .async = call_rcu_tasks, + .gp_barrier = rcu_barrier_tasks, + .sync = synchronize_rcu_tasks, + .exp_sync = synchronize_rcu_tasks, + .name = "tasks" +}; + +static unsigned long rcuperf_seq_diff(unsigned long new, unsigned long old) +{ + if (!cur_ops->gp_diff) + return new - old; + return cur_ops->gp_diff(new, old); +} + +/* + * If performance tests complete, wait for shutdown to commence. + */ +static void rcu_perf_wait_shutdown(void) +{ + cond_resched_tasks_rcu_qs(); + if (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters) + return; + while (!torture_must_stop()) + schedule_timeout_uninterruptible(1); +} + +/* + * RCU perf reader kthread. Repeatedly does empty RCU read-side + * critical section, minimizing update-side interference. + */ +static int +rcu_perf_reader(void *arg) +{ + unsigned long flags; + int idx; + long me = (long)arg; + + VERBOSE_PERFOUT_STRING("rcu_perf_reader task started"); + set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids)); + set_user_nice(current, MAX_NICE); + atomic_inc(&n_rcu_perf_reader_started); + + do { + local_irq_save(flags); + idx = cur_ops->readlock(); + cur_ops->readunlock(idx); + local_irq_restore(flags); + rcu_perf_wait_shutdown(); + } while (!torture_must_stop()); + torture_kthread_stopping("rcu_perf_reader"); + return 0; +} + +/* + * Callback function for asynchronous grace periods from rcu_perf_writer(). + */ +static void rcu_perf_async_cb(struct rcu_head *rhp) +{ + atomic_dec(this_cpu_ptr(&n_async_inflight)); + kfree(rhp); +} + +/* + * RCU perf writer kthread. Repeatedly does a grace period. + */ +static int +rcu_perf_writer(void *arg) +{ + int i = 0; + int i_max; + long me = (long)arg; + struct rcu_head *rhp = NULL; + struct sched_param sp; + bool started = false, done = false, alldone = false; + u64 t; + u64 *wdp; + u64 *wdpp = writer_durations[me]; + + VERBOSE_PERFOUT_STRING("rcu_perf_writer task started"); + WARN_ON(!wdpp); + set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids)); + sp.sched_priority = 1; + sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); + + if (holdoff) + schedule_timeout_uninterruptible(holdoff * HZ); + + t = ktime_get_mono_fast_ns(); + if (atomic_inc_return(&n_rcu_perf_writer_started) >= nrealwriters) { + t_rcu_perf_writer_started = t; + if (gp_exp) { + b_rcu_perf_writer_started = + cur_ops->exp_completed() / 2; + } else { + b_rcu_perf_writer_started = cur_ops->get_gp_seq(); + } + } + + do { + if (writer_holdoff) + udelay(writer_holdoff); + wdp = &wdpp[i]; + *wdp = ktime_get_mono_fast_ns(); + if (gp_async) { +retry: + if (!rhp) + rhp = kmalloc(sizeof(*rhp), GFP_KERNEL); + if (rhp && atomic_read(this_cpu_ptr(&n_async_inflight)) < gp_async_max) { + rcu_perf_writer_state = RTWS_ASYNC; + atomic_inc(this_cpu_ptr(&n_async_inflight)); + cur_ops->async(rhp, rcu_perf_async_cb); + rhp = NULL; + } else if (!kthread_should_stop()) { + rcu_perf_writer_state = RTWS_BARRIER; + cur_ops->gp_barrier(); + goto retry; + } else { + kfree(rhp); /* Because we are stopping. */ + } + } else if (gp_exp) { + rcu_perf_writer_state = RTWS_EXP_SYNC; + cur_ops->exp_sync(); + } else { + rcu_perf_writer_state = RTWS_SYNC; + cur_ops->sync(); + } + rcu_perf_writer_state = RTWS_IDLE; + t = ktime_get_mono_fast_ns(); + *wdp = t - *wdp; + i_max = i; + if (!started && + atomic_read(&n_rcu_perf_writer_started) >= nrealwriters) + started = true; + if (!done && i >= MIN_MEAS) { + done = true; + sp.sched_priority = 0; + sched_setscheduler_nocheck(current, + SCHED_NORMAL, &sp); + pr_alert("%s%s rcu_perf_writer %ld has %d measurements\n", + perf_type, PERF_FLAG, me, MIN_MEAS); + if (atomic_inc_return(&n_rcu_perf_writer_finished) >= + nrealwriters) { + schedule_timeout_interruptible(10); + rcu_ftrace_dump(DUMP_ALL); + PERFOUT_STRING("Test complete"); + t_rcu_perf_writer_finished = t; + if (gp_exp) { + b_rcu_perf_writer_finished = + cur_ops->exp_completed() / 2; + } else { + b_rcu_perf_writer_finished = + cur_ops->get_gp_seq(); + } + if (shutdown) { + smp_mb(); /* Assign before wake. */ + wake_up(&shutdown_wq); + } + } + } + if (done && !alldone && + atomic_read(&n_rcu_perf_writer_finished) >= nrealwriters) + alldone = true; + if (started && !alldone && i < MAX_MEAS - 1) + i++; + rcu_perf_wait_shutdown(); + } while (!torture_must_stop()); + if (gp_async) { + rcu_perf_writer_state = RTWS_BARRIER; + cur_ops->gp_barrier(); + } + rcu_perf_writer_state = RTWS_STOPPING; + writer_n_durations[me] = i_max; + torture_kthread_stopping("rcu_perf_writer"); + return 0; +} + +static void +rcu_perf_print_module_parms(struct rcu_perf_ops *cur_ops, const char *tag) +{ + pr_alert("%s" PERF_FLAG + "--- %s: nreaders=%d nwriters=%d verbose=%d shutdown=%d\n", + perf_type, tag, nrealreaders, nrealwriters, verbose, shutdown); +} + +static void +rcu_perf_cleanup(void) +{ + int i; + int j; + int ngps = 0; + u64 *wdp; + u64 *wdpp; + + /* + * Would like warning at start, but everything is expedited + * during the mid-boot phase, so have to wait till the end. + */ + if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp) + VERBOSE_PERFOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!"); + if (rcu_gp_is_normal() && gp_exp) + VERBOSE_PERFOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!"); + if (gp_exp && gp_async) + VERBOSE_PERFOUT_ERRSTRING("No expedited async GPs, so went with async!"); + + if (torture_cleanup_begin()) + return; + if (!cur_ops) { + torture_cleanup_end(); + return; + } + + if (reader_tasks) { + for (i = 0; i < nrealreaders; i++) + torture_stop_kthread(rcu_perf_reader, + reader_tasks[i]); + kfree(reader_tasks); + } + + if (writer_tasks) { + for (i = 0; i < nrealwriters; i++) { + torture_stop_kthread(rcu_perf_writer, + writer_tasks[i]); + if (!writer_n_durations) + continue; + j = writer_n_durations[i]; + pr_alert("%s%s writer %d gps: %d\n", + perf_type, PERF_FLAG, i, j); + ngps += j; + } + pr_alert("%s%s start: %llu end: %llu duration: %llu gps: %d batches: %ld\n", + perf_type, PERF_FLAG, + t_rcu_perf_writer_started, t_rcu_perf_writer_finished, + t_rcu_perf_writer_finished - + t_rcu_perf_writer_started, + ngps, + rcuperf_seq_diff(b_rcu_perf_writer_finished, + b_rcu_perf_writer_started)); + for (i = 0; i < nrealwriters; i++) { + if (!writer_durations) + break; + if (!writer_n_durations) + continue; + wdpp = writer_durations[i]; + if (!wdpp) + continue; + for (j = 0; j <= writer_n_durations[i]; j++) { + wdp = &wdpp[j]; + pr_alert("%s%s %4d writer-duration: %5d %llu\n", + perf_type, PERF_FLAG, + i, j, *wdp); + if (j % 100 == 0) + schedule_timeout_uninterruptible(1); + } + kfree(writer_durations[i]); + } + kfree(writer_tasks); + kfree(writer_durations); + kfree(writer_n_durations); + } + + /* Do flavor-specific cleanup operations. */ + if (cur_ops->cleanup != NULL) + cur_ops->cleanup(); + + torture_cleanup_end(); +} + +/* + * Return the number if non-negative. If -1, the number of CPUs. + * If less than -1, that much less than the number of CPUs, but + * at least one. + */ +static int compute_real(int n) +{ + int nr; + + if (n >= 0) { + nr = n; + } else { + nr = num_online_cpus() + 1 + n; + if (nr <= 0) + nr = 1; + } + return nr; +} + +/* + * RCU perf shutdown kthread. Just waits to be awakened, then shuts + * down system. + */ +static int +rcu_perf_shutdown(void *arg) +{ + do { + wait_event(shutdown_wq, + atomic_read(&n_rcu_perf_writer_finished) >= + nrealwriters); + } while (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters); + smp_mb(); /* Wake before output. */ + rcu_perf_cleanup(); + kernel_power_off(); + return -EINVAL; +} + +static int __init +rcu_perf_init(void) +{ + long i; + int firsterr = 0; + static struct rcu_perf_ops *perf_ops[] = { + &rcu_ops, &rcu_bh_ops, &srcu_ops, &srcud_ops, &sched_ops, + &tasks_ops, + }; + + if (!torture_init_begin(perf_type, verbose)) + return -EBUSY; + + /* Process args and tell the world that the perf'er is on the job. */ + for (i = 0; i < ARRAY_SIZE(perf_ops); i++) { + cur_ops = perf_ops[i]; + if (strcmp(perf_type, cur_ops->name) == 0) + break; + } + if (i == ARRAY_SIZE(perf_ops)) { + pr_alert("rcu-perf: invalid perf type: \"%s\"\n", perf_type); + pr_alert("rcu-perf types:"); + for (i = 0; i < ARRAY_SIZE(perf_ops); i++) + pr_cont(" %s", perf_ops[i]->name); + pr_cont("\n"); + firsterr = -EINVAL; + cur_ops = NULL; + goto unwind; + } + if (cur_ops->init) + cur_ops->init(); + + nrealwriters = compute_real(nwriters); + nrealreaders = compute_real(nreaders); + atomic_set(&n_rcu_perf_reader_started, 0); + atomic_set(&n_rcu_perf_writer_started, 0); + atomic_set(&n_rcu_perf_writer_finished, 0); + rcu_perf_print_module_parms(cur_ops, "Start of test"); + + /* Start up the kthreads. */ + + if (shutdown) { + init_waitqueue_head(&shutdown_wq); + firsterr = torture_create_kthread(rcu_perf_shutdown, NULL, + shutdown_task); + if (firsterr) + goto unwind; + schedule_timeout_uninterruptible(1); + } + reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]), + GFP_KERNEL); + if (reader_tasks == NULL) { + VERBOSE_PERFOUT_ERRSTRING("out of memory"); + firsterr = -ENOMEM; + goto unwind; + } + for (i = 0; i < nrealreaders; i++) { + firsterr = torture_create_kthread(rcu_perf_reader, (void *)i, + reader_tasks[i]); + if (firsterr) + goto unwind; + } + while (atomic_read(&n_rcu_perf_reader_started) < nrealreaders) + schedule_timeout_uninterruptible(1); + writer_tasks = kcalloc(nrealwriters, sizeof(reader_tasks[0]), + GFP_KERNEL); + writer_durations = kcalloc(nrealwriters, sizeof(*writer_durations), + GFP_KERNEL); + writer_n_durations = + kcalloc(nrealwriters, sizeof(*writer_n_durations), + GFP_KERNEL); + if (!writer_tasks || !writer_durations || !writer_n_durations) { + VERBOSE_PERFOUT_ERRSTRING("out of memory"); + firsterr = -ENOMEM; + goto unwind; + } + for (i = 0; i < nrealwriters; i++) { + writer_durations[i] = + kcalloc(MAX_MEAS, sizeof(*writer_durations[i]), + GFP_KERNEL); + if (!writer_durations[i]) { + firsterr = -ENOMEM; + goto unwind; + } + firsterr = torture_create_kthread(rcu_perf_writer, (void *)i, + writer_tasks[i]); + if (firsterr) + goto unwind; + } + torture_init_end(); + return 0; + +unwind: + torture_init_end(); + rcu_perf_cleanup(); + return firsterr; +} + +module_init(rcu_perf_init); +module_exit(rcu_perf_cleanup); diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c new file mode 100644 index 000000000..0b7af7e2b --- /dev/null +++ b/kernel/rcu/rcutorture.c @@ -0,0 +1,2141 @@ +/* + * Read-Copy Update module-based torture test facility + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright (C) IBM Corporation, 2005, 2006 + * + * Authors: Paul E. McKenney <paulmck@us.ibm.com> + * Josh Triplett <josh@joshtriplett.org> + * + * See also: Documentation/RCU/torture.txt + */ + +#define pr_fmt(fmt) fmt + +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/module.h> +#include <linux/kthread.h> +#include <linux/err.h> +#include <linux/spinlock.h> +#include <linux/smp.h> +#include <linux/rcupdate.h> +#include <linux/interrupt.h> +#include <linux/sched/signal.h> +#include <uapi/linux/sched/types.h> +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/completion.h> +#include <linux/moduleparam.h> +#include <linux/percpu.h> +#include <linux/notifier.h> +#include <linux/reboot.h> +#include <linux/freezer.h> +#include <linux/cpu.h> +#include <linux/delay.h> +#include <linux/stat.h> +#include <linux/srcu.h> +#include <linux/slab.h> +#include <linux/trace_clock.h> +#include <asm/byteorder.h> +#include <linux/torture.h> +#include <linux/vmalloc.h> +#include <linux/sched/debug.h> +#include <linux/sched/sysctl.h> + +#include "rcu.h" + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and Josh Triplett <josh@joshtriplett.org>"); + + +/* Bits for ->extendables field, extendables param, and related definitions. */ +#define RCUTORTURE_RDR_SHIFT 8 /* Put SRCU index in upper bits. */ +#define RCUTORTURE_RDR_MASK ((1 << RCUTORTURE_RDR_SHIFT) - 1) +#define RCUTORTURE_RDR_BH 0x1 /* Extend readers by disabling bh. */ +#define RCUTORTURE_RDR_IRQ 0x2 /* ... disabling interrupts. */ +#define RCUTORTURE_RDR_PREEMPT 0x4 /* ... disabling preemption. */ +#define RCUTORTURE_RDR_RCU 0x8 /* ... entering another RCU reader. */ +#define RCUTORTURE_RDR_NBITS 4 /* Number of bits defined above. */ +#define RCUTORTURE_MAX_EXTEND (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | \ + RCUTORTURE_RDR_PREEMPT) +#define RCUTORTURE_RDR_MAX_LOOPS 0x7 /* Maximum reader extensions. */ + /* Must be power of two minus one. */ + +torture_param(int, cbflood_inter_holdoff, HZ, + "Holdoff between floods (jiffies)"); +torture_param(int, cbflood_intra_holdoff, 1, + "Holdoff between bursts (jiffies)"); +torture_param(int, cbflood_n_burst, 3, "# bursts in flood, zero to disable"); +torture_param(int, cbflood_n_per_burst, 20000, + "# callbacks per burst in flood"); +torture_param(int, extendables, RCUTORTURE_MAX_EXTEND, + "Extend readers by disabling bh (1), irqs (2), or preempt (4)"); +torture_param(int, fqs_duration, 0, + "Duration of fqs bursts (us), 0 to disable"); +torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)"); +torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)"); +torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives"); +torture_param(bool, gp_exp, false, "Use expedited GP wait primitives"); +torture_param(bool, gp_normal, false, + "Use normal (non-expedited) GP wait primitives"); +torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives"); +torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers"); +torture_param(int, n_barrier_cbs, 0, + "# of callbacks/kthreads for barrier testing"); +torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads"); +torture_param(int, nreaders, -1, "Number of RCU reader threads"); +torture_param(int, object_debug, 0, + "Enable debug-object double call_rcu() testing"); +torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)"); +torture_param(int, onoff_interval, 0, + "Time between CPU hotplugs (jiffies), 0=disable"); +torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles"); +torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable."); +torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable."); +torture_param(int, stall_cpu_holdoff, 10, + "Time to wait before starting stall (s)."); +torture_param(int, stall_cpu_irqsoff, 0, "Disable interrupts while stalling."); +torture_param(int, stat_interval, 60, + "Number of seconds between stats printk()s"); +torture_param(int, stutter, 5, "Number of seconds to run/halt test"); +torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes."); +torture_param(int, test_boost_duration, 4, + "Duration of each boost test, seconds."); +torture_param(int, test_boost_interval, 7, + "Interval between boost tests, seconds."); +torture_param(bool, test_no_idle_hz, true, + "Test support for tickless idle CPUs"); +torture_param(int, verbose, 1, + "Enable verbose debugging printk()s"); + +static char *torture_type = "rcu"; +module_param(torture_type, charp, 0444); +MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, ...)"); + +static int nrealreaders; +static int ncbflooders; +static struct task_struct *writer_task; +static struct task_struct **fakewriter_tasks; +static struct task_struct **reader_tasks; +static struct task_struct *stats_task; +static struct task_struct **cbflood_task; +static struct task_struct *fqs_task; +static struct task_struct *boost_tasks[NR_CPUS]; +static struct task_struct *stall_task; +static struct task_struct **barrier_cbs_tasks; +static struct task_struct *barrier_task; + +#define RCU_TORTURE_PIPE_LEN 10 + +struct rcu_torture { + struct rcu_head rtort_rcu; + int rtort_pipe_count; + struct list_head rtort_free; + int rtort_mbtest; +}; + +static LIST_HEAD(rcu_torture_freelist); +static struct rcu_torture __rcu *rcu_torture_current; +static unsigned long rcu_torture_current_version; +static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN]; +static DEFINE_SPINLOCK(rcu_torture_lock); +static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count); +static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch); +static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1]; +static atomic_t n_rcu_torture_alloc; +static atomic_t n_rcu_torture_alloc_fail; +static atomic_t n_rcu_torture_free; +static atomic_t n_rcu_torture_mberror; +static atomic_t n_rcu_torture_error; +static long n_rcu_torture_barrier_error; +static long n_rcu_torture_boost_ktrerror; +static long n_rcu_torture_boost_rterror; +static long n_rcu_torture_boost_failure; +static long n_rcu_torture_boosts; +static atomic_long_t n_rcu_torture_timers; +static long n_barrier_attempts; +static long n_barrier_successes; /* did rcu_barrier test succeed? */ +static atomic_long_t n_cbfloods; +static struct list_head rcu_torture_removed; + +static int rcu_torture_writer_state; +#define RTWS_FIXED_DELAY 0 +#define RTWS_DELAY 1 +#define RTWS_REPLACE 2 +#define RTWS_DEF_FREE 3 +#define RTWS_EXP_SYNC 4 +#define RTWS_COND_GET 5 +#define RTWS_COND_SYNC 6 +#define RTWS_SYNC 7 +#define RTWS_STUTTER 8 +#define RTWS_STOPPING 9 +static const char * const rcu_torture_writer_state_names[] = { + "RTWS_FIXED_DELAY", + "RTWS_DELAY", + "RTWS_REPLACE", + "RTWS_DEF_FREE", + "RTWS_EXP_SYNC", + "RTWS_COND_GET", + "RTWS_COND_SYNC", + "RTWS_SYNC", + "RTWS_STUTTER", + "RTWS_STOPPING", +}; + +static const char *rcu_torture_writer_state_getname(void) +{ + unsigned int i = READ_ONCE(rcu_torture_writer_state); + + if (i >= ARRAY_SIZE(rcu_torture_writer_state_names)) + return "???"; + return rcu_torture_writer_state_names[i]; +} + +#if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) +#define rcu_can_boost() 1 +#else /* #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */ +#define rcu_can_boost() 0 +#endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */ + +#ifdef CONFIG_RCU_TRACE +static u64 notrace rcu_trace_clock_local(void) +{ + u64 ts = trace_clock_local(); + + (void)do_div(ts, NSEC_PER_USEC); + return ts; +} +#else /* #ifdef CONFIG_RCU_TRACE */ +static u64 notrace rcu_trace_clock_local(void) +{ + return 0ULL; +} +#endif /* #else #ifdef CONFIG_RCU_TRACE */ + +static unsigned long boost_starttime; /* jiffies of next boost test start. */ +static DEFINE_MUTEX(boost_mutex); /* protect setting boost_starttime */ + /* and boost task create/destroy. */ +static atomic_t barrier_cbs_count; /* Barrier callbacks registered. */ +static bool barrier_phase; /* Test phase. */ +static atomic_t barrier_cbs_invoked; /* Barrier callbacks invoked. */ +static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */ +static DECLARE_WAIT_QUEUE_HEAD(barrier_wq); + +/* + * Allocate an element from the rcu_tortures pool. + */ +static struct rcu_torture * +rcu_torture_alloc(void) +{ + struct list_head *p; + + spin_lock_bh(&rcu_torture_lock); + if (list_empty(&rcu_torture_freelist)) { + atomic_inc(&n_rcu_torture_alloc_fail); + spin_unlock_bh(&rcu_torture_lock); + return NULL; + } + atomic_inc(&n_rcu_torture_alloc); + p = rcu_torture_freelist.next; + list_del_init(p); + spin_unlock_bh(&rcu_torture_lock); + return container_of(p, struct rcu_torture, rtort_free); +} + +/* + * Free an element to the rcu_tortures pool. + */ +static void +rcu_torture_free(struct rcu_torture *p) +{ + atomic_inc(&n_rcu_torture_free); + spin_lock_bh(&rcu_torture_lock); + list_add_tail(&p->rtort_free, &rcu_torture_freelist); + spin_unlock_bh(&rcu_torture_lock); +} + +/* + * Operations vector for selecting different types of tests. + */ + +struct rcu_torture_ops { + int ttype; + void (*init)(void); + void (*cleanup)(void); + int (*readlock)(void); + void (*read_delay)(struct torture_random_state *rrsp); + void (*readunlock)(int idx); + unsigned long (*get_gp_seq)(void); + unsigned long (*gp_diff)(unsigned long new, unsigned long old); + void (*deferred_free)(struct rcu_torture *p); + void (*sync)(void); + void (*exp_sync)(void); + unsigned long (*get_state)(void); + void (*cond_sync)(unsigned long oldstate); + call_rcu_func_t call; + void (*cb_barrier)(void); + void (*fqs)(void); + void (*stats)(void); + int irq_capable; + int can_boost; + int extendables; + int ext_irq_conflict; + const char *name; +}; + +static struct rcu_torture_ops *cur_ops; + +/* + * Definitions for rcu torture testing. + */ + +static int rcu_torture_read_lock(void) __acquires(RCU) +{ + rcu_read_lock(); + return 0; +} + +static void rcu_read_delay(struct torture_random_state *rrsp) +{ + unsigned long started; + unsigned long completed; + const unsigned long shortdelay_us = 200; + const unsigned long longdelay_ms = 50; + unsigned long long ts; + + /* We want a short delay sometimes to make a reader delay the grace + * period, and we want a long delay occasionally to trigger + * force_quiescent_state. */ + + if (!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) { + started = cur_ops->get_gp_seq(); + ts = rcu_trace_clock_local(); + mdelay(longdelay_ms); + completed = cur_ops->get_gp_seq(); + do_trace_rcu_torture_read(cur_ops->name, NULL, ts, + started, completed); + } + if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us))) + udelay(shortdelay_us); + if (!preempt_count() && + !(torture_random(rrsp) % (nrealreaders * 500))) + torture_preempt_schedule(); /* QS only if preemptible. */ +} + +static void rcu_torture_read_unlock(int idx) __releases(RCU) +{ + rcu_read_unlock(); +} + +/* + * Update callback in the pipe. This should be invoked after a grace period. + */ +static bool +rcu_torture_pipe_update_one(struct rcu_torture *rp) +{ + int i; + + i = rp->rtort_pipe_count; + if (i > RCU_TORTURE_PIPE_LEN) + i = RCU_TORTURE_PIPE_LEN; + atomic_inc(&rcu_torture_wcount[i]); + if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) { + rp->rtort_mbtest = 0; + return true; + } + return false; +} + +/* + * Update all callbacks in the pipe. Suitable for synchronous grace-period + * primitives. + */ +static void +rcu_torture_pipe_update(struct rcu_torture *old_rp) +{ + struct rcu_torture *rp; + struct rcu_torture *rp1; + + if (old_rp) + list_add(&old_rp->rtort_free, &rcu_torture_removed); + list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) { + if (rcu_torture_pipe_update_one(rp)) { + list_del(&rp->rtort_free); + rcu_torture_free(rp); + } + } +} + +static void +rcu_torture_cb(struct rcu_head *p) +{ + struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu); + + if (torture_must_stop_irq()) { + /* Test is ending, just drop callbacks on the floor. */ + /* The next initialization will pick up the pieces. */ + return; + } + if (rcu_torture_pipe_update_one(rp)) + rcu_torture_free(rp); + else + cur_ops->deferred_free(rp); +} + +static unsigned long rcu_no_completed(void) +{ + return 0; +} + +static void rcu_torture_deferred_free(struct rcu_torture *p) +{ + call_rcu(&p->rtort_rcu, rcu_torture_cb); +} + +static void rcu_sync_torture_init(void) +{ + INIT_LIST_HEAD(&rcu_torture_removed); +} + +static struct rcu_torture_ops rcu_ops = { + .ttype = RCU_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = rcu_torture_read_lock, + .read_delay = rcu_read_delay, + .readunlock = rcu_torture_read_unlock, + .get_gp_seq = rcu_get_gp_seq, + .gp_diff = rcu_seq_diff, + .deferred_free = rcu_torture_deferred_free, + .sync = synchronize_rcu, + .exp_sync = synchronize_rcu_expedited, + .get_state = get_state_synchronize_rcu, + .cond_sync = cond_synchronize_rcu, + .call = call_rcu, + .cb_barrier = rcu_barrier, + .fqs = rcu_force_quiescent_state, + .stats = NULL, + .irq_capable = 1, + .can_boost = rcu_can_boost(), + .name = "rcu" +}; + +/* + * Definitions for rcu_bh torture testing. + */ + +static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH) +{ + rcu_read_lock_bh(); + return 0; +} + +static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH) +{ + rcu_read_unlock_bh(); +} + +static void rcu_bh_torture_deferred_free(struct rcu_torture *p) +{ + call_rcu_bh(&p->rtort_rcu, rcu_torture_cb); +} + +static struct rcu_torture_ops rcu_bh_ops = { + .ttype = RCU_BH_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = rcu_bh_torture_read_lock, + .read_delay = rcu_read_delay, /* just reuse rcu's version. */ + .readunlock = rcu_bh_torture_read_unlock, + .get_gp_seq = rcu_bh_get_gp_seq, + .gp_diff = rcu_seq_diff, + .deferred_free = rcu_bh_torture_deferred_free, + .sync = synchronize_rcu_bh, + .exp_sync = synchronize_rcu_bh_expedited, + .call = call_rcu_bh, + .cb_barrier = rcu_barrier_bh, + .fqs = rcu_bh_force_quiescent_state, + .stats = NULL, + .irq_capable = 1, + .extendables = (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ), + .ext_irq_conflict = RCUTORTURE_RDR_RCU, + .name = "rcu_bh" +}; + +/* + * Don't even think about trying any of these in real life!!! + * The names includes "busted", and they really means it! + * The only purpose of these functions is to provide a buggy RCU + * implementation to make sure that rcutorture correctly emits + * buggy-RCU error messages. + */ +static void rcu_busted_torture_deferred_free(struct rcu_torture *p) +{ + /* This is a deliberate bug for testing purposes only! */ + rcu_torture_cb(&p->rtort_rcu); +} + +static void synchronize_rcu_busted(void) +{ + /* This is a deliberate bug for testing purposes only! */ +} + +static void +call_rcu_busted(struct rcu_head *head, rcu_callback_t func) +{ + /* This is a deliberate bug for testing purposes only! */ + func(head); +} + +static struct rcu_torture_ops rcu_busted_ops = { + .ttype = INVALID_RCU_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = rcu_torture_read_lock, + .read_delay = rcu_read_delay, /* just reuse rcu's version. */ + .readunlock = rcu_torture_read_unlock, + .get_gp_seq = rcu_no_completed, + .deferred_free = rcu_busted_torture_deferred_free, + .sync = synchronize_rcu_busted, + .exp_sync = synchronize_rcu_busted, + .call = call_rcu_busted, + .cb_barrier = NULL, + .fqs = NULL, + .stats = NULL, + .irq_capable = 1, + .name = "busted" +}; + +/* + * Definitions for srcu torture testing. + */ + +DEFINE_STATIC_SRCU(srcu_ctl); +static struct srcu_struct srcu_ctld; +static struct srcu_struct *srcu_ctlp = &srcu_ctl; + +static int srcu_torture_read_lock(void) __acquires(srcu_ctlp) +{ + return srcu_read_lock(srcu_ctlp); +} + +static void srcu_read_delay(struct torture_random_state *rrsp) +{ + long delay; + const long uspertick = 1000000 / HZ; + const long longdelay = 10; + + /* We want there to be long-running readers, but not all the time. */ + + delay = torture_random(rrsp) % + (nrealreaders * 2 * longdelay * uspertick); + if (!delay && in_task()) + schedule_timeout_interruptible(longdelay); + else + rcu_read_delay(rrsp); +} + +static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp) +{ + srcu_read_unlock(srcu_ctlp, idx); +} + +static unsigned long srcu_torture_completed(void) +{ + return srcu_batches_completed(srcu_ctlp); +} + +static void srcu_torture_deferred_free(struct rcu_torture *rp) +{ + call_srcu(srcu_ctlp, &rp->rtort_rcu, rcu_torture_cb); +} + +static void srcu_torture_synchronize(void) +{ + synchronize_srcu(srcu_ctlp); +} + +static void srcu_torture_call(struct rcu_head *head, + rcu_callback_t func) +{ + call_srcu(srcu_ctlp, head, func); +} + +static void srcu_torture_barrier(void) +{ + srcu_barrier(srcu_ctlp); +} + +static void srcu_torture_stats(void) +{ + srcu_torture_stats_print(srcu_ctlp, torture_type, TORTURE_FLAG); +} + +static void srcu_torture_synchronize_expedited(void) +{ + synchronize_srcu_expedited(srcu_ctlp); +} + +static struct rcu_torture_ops srcu_ops = { + .ttype = SRCU_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = srcu_torture_read_lock, + .read_delay = srcu_read_delay, + .readunlock = srcu_torture_read_unlock, + .get_gp_seq = srcu_torture_completed, + .deferred_free = srcu_torture_deferred_free, + .sync = srcu_torture_synchronize, + .exp_sync = srcu_torture_synchronize_expedited, + .call = srcu_torture_call, + .cb_barrier = srcu_torture_barrier, + .stats = srcu_torture_stats, + .irq_capable = 1, + .name = "srcu" +}; + +static void srcu_torture_init(void) +{ + rcu_sync_torture_init(); + WARN_ON(init_srcu_struct(&srcu_ctld)); + srcu_ctlp = &srcu_ctld; +} + +static void srcu_torture_cleanup(void) +{ + static DEFINE_TORTURE_RANDOM(rand); + + if (torture_random(&rand) & 0x800) + cleanup_srcu_struct(&srcu_ctld); + else + cleanup_srcu_struct_quiesced(&srcu_ctld); + srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */ +} + +/* As above, but dynamically allocated. */ +static struct rcu_torture_ops srcud_ops = { + .ttype = SRCU_FLAVOR, + .init = srcu_torture_init, + .cleanup = srcu_torture_cleanup, + .readlock = srcu_torture_read_lock, + .read_delay = srcu_read_delay, + .readunlock = srcu_torture_read_unlock, + .get_gp_seq = srcu_torture_completed, + .deferred_free = srcu_torture_deferred_free, + .sync = srcu_torture_synchronize, + .exp_sync = srcu_torture_synchronize_expedited, + .call = srcu_torture_call, + .cb_barrier = srcu_torture_barrier, + .stats = srcu_torture_stats, + .irq_capable = 1, + .name = "srcud" +}; + +/* As above, but broken due to inappropriate reader extension. */ +static struct rcu_torture_ops busted_srcud_ops = { + .ttype = SRCU_FLAVOR, + .init = srcu_torture_init, + .cleanup = srcu_torture_cleanup, + .readlock = srcu_torture_read_lock, + .read_delay = rcu_read_delay, + .readunlock = srcu_torture_read_unlock, + .get_gp_seq = srcu_torture_completed, + .deferred_free = srcu_torture_deferred_free, + .sync = srcu_torture_synchronize, + .exp_sync = srcu_torture_synchronize_expedited, + .call = srcu_torture_call, + .cb_barrier = srcu_torture_barrier, + .stats = srcu_torture_stats, + .irq_capable = 1, + .extendables = RCUTORTURE_MAX_EXTEND, + .name = "busted_srcud" +}; + +/* + * Definitions for sched torture testing. + */ + +static int sched_torture_read_lock(void) +{ + preempt_disable(); + return 0; +} + +static void sched_torture_read_unlock(int idx) +{ + preempt_enable(); +} + +static void rcu_sched_torture_deferred_free(struct rcu_torture *p) +{ + call_rcu_sched(&p->rtort_rcu, rcu_torture_cb); +} + +static struct rcu_torture_ops sched_ops = { + .ttype = RCU_SCHED_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = sched_torture_read_lock, + .read_delay = rcu_read_delay, /* just reuse rcu's version. */ + .readunlock = sched_torture_read_unlock, + .get_gp_seq = rcu_sched_get_gp_seq, + .gp_diff = rcu_seq_diff, + .deferred_free = rcu_sched_torture_deferred_free, + .sync = synchronize_sched, + .exp_sync = synchronize_sched_expedited, + .get_state = get_state_synchronize_sched, + .cond_sync = cond_synchronize_sched, + .call = call_rcu_sched, + .cb_barrier = rcu_barrier_sched, + .fqs = rcu_sched_force_quiescent_state, + .stats = NULL, + .irq_capable = 1, + .extendables = RCUTORTURE_MAX_EXTEND, + .name = "sched" +}; + +/* + * Definitions for RCU-tasks torture testing. + */ + +static int tasks_torture_read_lock(void) +{ + return 0; +} + +static void tasks_torture_read_unlock(int idx) +{ +} + +static void rcu_tasks_torture_deferred_free(struct rcu_torture *p) +{ + call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb); +} + +static struct rcu_torture_ops tasks_ops = { + .ttype = RCU_TASKS_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = tasks_torture_read_lock, + .read_delay = rcu_read_delay, /* just reuse rcu's version. */ + .readunlock = tasks_torture_read_unlock, + .get_gp_seq = rcu_no_completed, + .deferred_free = rcu_tasks_torture_deferred_free, + .sync = synchronize_rcu_tasks, + .exp_sync = synchronize_rcu_tasks, + .call = call_rcu_tasks, + .cb_barrier = rcu_barrier_tasks, + .fqs = NULL, + .stats = NULL, + .irq_capable = 1, + .name = "tasks" +}; + +static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old) +{ + if (!cur_ops->gp_diff) + return new - old; + return cur_ops->gp_diff(new, old); +} + +static bool __maybe_unused torturing_tasks(void) +{ + return cur_ops == &tasks_ops; +} + +/* + * RCU torture priority-boost testing. Runs one real-time thread per + * CPU for moderate bursts, repeatedly registering RCU callbacks and + * spinning waiting for them to be invoked. If a given callback takes + * too long to be invoked, we assume that priority inversion has occurred. + */ + +struct rcu_boost_inflight { + struct rcu_head rcu; + int inflight; +}; + +static void rcu_torture_boost_cb(struct rcu_head *head) +{ + struct rcu_boost_inflight *rbip = + container_of(head, struct rcu_boost_inflight, rcu); + + /* Ensure RCU-core accesses precede clearing ->inflight */ + smp_store_release(&rbip->inflight, 0); +} + +static int old_rt_runtime = -1; + +static void rcu_torture_disable_rt_throttle(void) +{ + /* + * Disable RT throttling so that rcutorture's boost threads don't get + * throttled. Only possible if rcutorture is built-in otherwise the + * user should manually do this by setting the sched_rt_period_us and + * sched_rt_runtime sysctls. + */ + if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime != -1) + return; + + old_rt_runtime = sysctl_sched_rt_runtime; + sysctl_sched_rt_runtime = -1; +} + +static void rcu_torture_enable_rt_throttle(void) +{ + if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime == -1) + return; + + sysctl_sched_rt_runtime = old_rt_runtime; + old_rt_runtime = -1; +} + +static bool rcu_torture_boost_failed(unsigned long start, unsigned long end) +{ + if (end - start > test_boost_duration * HZ - HZ / 2) { + VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed"); + n_rcu_torture_boost_failure++; + + return true; /* failed */ + } + + return false; /* passed */ +} + +static int rcu_torture_boost(void *arg) +{ + unsigned long call_rcu_time; + unsigned long endtime; + unsigned long oldstarttime; + struct rcu_boost_inflight rbi = { .inflight = 0 }; + struct sched_param sp; + + VERBOSE_TOROUT_STRING("rcu_torture_boost started"); + + /* Set real-time priority. */ + sp.sched_priority = 1; + if (sched_setscheduler(current, SCHED_FIFO, &sp) < 0) { + VERBOSE_TOROUT_STRING("rcu_torture_boost RT prio failed!"); + n_rcu_torture_boost_rterror++; + } + + init_rcu_head_on_stack(&rbi.rcu); + /* Each pass through the following loop does one boost-test cycle. */ + do { + /* Track if the test failed already in this test interval? */ + bool failed = false; + + /* Increment n_rcu_torture_boosts once per boost-test */ + while (!kthread_should_stop()) { + if (mutex_trylock(&boost_mutex)) { + n_rcu_torture_boosts++; + mutex_unlock(&boost_mutex); + break; + } + schedule_timeout_uninterruptible(1); + } + if (kthread_should_stop()) + goto checkwait; + + /* Wait for the next test interval. */ + oldstarttime = boost_starttime; + while (ULONG_CMP_LT(jiffies, oldstarttime)) { + schedule_timeout_interruptible(oldstarttime - jiffies); + stutter_wait("rcu_torture_boost"); + if (torture_must_stop()) + goto checkwait; + } + + /* Do one boost-test interval. */ + endtime = oldstarttime + test_boost_duration * HZ; + call_rcu_time = jiffies; + while (ULONG_CMP_LT(jiffies, endtime)) { + /* If we don't have a callback in flight, post one. */ + if (!smp_load_acquire(&rbi.inflight)) { + /* RCU core before ->inflight = 1. */ + smp_store_release(&rbi.inflight, 1); + call_rcu(&rbi.rcu, rcu_torture_boost_cb); + /* Check if the boost test failed */ + failed = failed || + rcu_torture_boost_failed(call_rcu_time, + jiffies); + call_rcu_time = jiffies; + } + stutter_wait("rcu_torture_boost"); + if (torture_must_stop()) + goto checkwait; + } + + /* + * If boost never happened, then inflight will always be 1, in + * this case the boost check would never happen in the above + * loop so do another one here. + */ + if (!failed && smp_load_acquire(&rbi.inflight)) + rcu_torture_boost_failed(call_rcu_time, jiffies); + + /* + * Set the start time of the next test interval. + * Yes, this is vulnerable to long delays, but such + * delays simply cause a false negative for the next + * interval. Besides, we are running at RT priority, + * so delays should be relatively rare. + */ + while (oldstarttime == boost_starttime && + !kthread_should_stop()) { + if (mutex_trylock(&boost_mutex)) { + boost_starttime = jiffies + + test_boost_interval * HZ; + mutex_unlock(&boost_mutex); + break; + } + schedule_timeout_uninterruptible(1); + } + + /* Go do the stutter. */ +checkwait: stutter_wait("rcu_torture_boost"); + } while (!torture_must_stop()); + + /* Clean up and exit. */ + while (!kthread_should_stop() || smp_load_acquire(&rbi.inflight)) { + torture_shutdown_absorb("rcu_torture_boost"); + schedule_timeout_uninterruptible(1); + } + destroy_rcu_head_on_stack(&rbi.rcu); + torture_kthread_stopping("rcu_torture_boost"); + return 0; +} + +static void rcu_torture_cbflood_cb(struct rcu_head *rhp) +{ +} + +/* + * RCU torture callback-flood kthread. Repeatedly induces bursts of calls + * to call_rcu() or analogous, increasing the probability of occurrence + * of callback-overflow corner cases. + */ +static int +rcu_torture_cbflood(void *arg) +{ + int err = 1; + int i; + int j; + struct rcu_head *rhp; + + if (cbflood_n_per_burst > 0 && + cbflood_inter_holdoff > 0 && + cbflood_intra_holdoff > 0 && + cur_ops->call && + cur_ops->cb_barrier) { + rhp = vmalloc(array3_size(cbflood_n_burst, + cbflood_n_per_burst, + sizeof(*rhp))); + err = !rhp; + } + if (err) { + VERBOSE_TOROUT_STRING("rcu_torture_cbflood disabled: Bad args or OOM"); + goto wait_for_stop; + } + VERBOSE_TOROUT_STRING("rcu_torture_cbflood task started"); + do { + schedule_timeout_interruptible(cbflood_inter_holdoff); + atomic_long_inc(&n_cbfloods); + WARN_ON(signal_pending(current)); + for (i = 0; i < cbflood_n_burst; i++) { + for (j = 0; j < cbflood_n_per_burst; j++) { + cur_ops->call(&rhp[i * cbflood_n_per_burst + j], + rcu_torture_cbflood_cb); + } + schedule_timeout_interruptible(cbflood_intra_holdoff); + WARN_ON(signal_pending(current)); + } + cur_ops->cb_barrier(); + stutter_wait("rcu_torture_cbflood"); + } while (!torture_must_stop()); + vfree(rhp); +wait_for_stop: + torture_kthread_stopping("rcu_torture_cbflood"); + return 0; +} + +/* + * RCU torture force-quiescent-state kthread. Repeatedly induces + * bursts of calls to force_quiescent_state(), increasing the probability + * of occurrence of some important types of race conditions. + */ +static int +rcu_torture_fqs(void *arg) +{ + unsigned long fqs_resume_time; + int fqs_burst_remaining; + + VERBOSE_TOROUT_STRING("rcu_torture_fqs task started"); + do { + fqs_resume_time = jiffies + fqs_stutter * HZ; + while (ULONG_CMP_LT(jiffies, fqs_resume_time) && + !kthread_should_stop()) { + schedule_timeout_interruptible(1); + } + fqs_burst_remaining = fqs_duration; + while (fqs_burst_remaining > 0 && + !kthread_should_stop()) { + cur_ops->fqs(); + udelay(fqs_holdoff); + fqs_burst_remaining -= fqs_holdoff; + } + stutter_wait("rcu_torture_fqs"); + } while (!torture_must_stop()); + torture_kthread_stopping("rcu_torture_fqs"); + return 0; +} + +/* + * RCU torture writer kthread. Repeatedly substitutes a new structure + * for that pointed to by rcu_torture_current, freeing the old structure + * after a series of grace periods (the "pipeline"). + */ +static int +rcu_torture_writer(void *arg) +{ + bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal(); + int expediting = 0; + unsigned long gp_snap; + bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal; + bool gp_sync1 = gp_sync; + int i; + struct rcu_torture *rp; + struct rcu_torture *old_rp; + static DEFINE_TORTURE_RANDOM(rand); + int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC, + RTWS_COND_GET, RTWS_SYNC }; + int nsynctypes = 0; + + VERBOSE_TOROUT_STRING("rcu_torture_writer task started"); + if (!can_expedite) + pr_alert("%s" TORTURE_FLAG + " GP expediting controlled from boot/sysfs for %s.\n", + torture_type, cur_ops->name); + + /* Initialize synctype[] array. If none set, take default. */ + if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_sync1) + gp_cond1 = gp_exp1 = gp_normal1 = gp_sync1 = true; + if (gp_cond1 && cur_ops->get_state && cur_ops->cond_sync) { + synctype[nsynctypes++] = RTWS_COND_GET; + pr_info("%s: Testing conditional GPs.\n", __func__); + } else if (gp_cond && (!cur_ops->get_state || !cur_ops->cond_sync)) { + pr_alert("%s: gp_cond without primitives.\n", __func__); + } + if (gp_exp1 && cur_ops->exp_sync) { + synctype[nsynctypes++] = RTWS_EXP_SYNC; + pr_info("%s: Testing expedited GPs.\n", __func__); + } else if (gp_exp && !cur_ops->exp_sync) { + pr_alert("%s: gp_exp without primitives.\n", __func__); + } + if (gp_normal1 && cur_ops->deferred_free) { + synctype[nsynctypes++] = RTWS_DEF_FREE; + pr_info("%s: Testing asynchronous GPs.\n", __func__); + } else if (gp_normal && !cur_ops->deferred_free) { + pr_alert("%s: gp_normal without primitives.\n", __func__); + } + if (gp_sync1 && cur_ops->sync) { + synctype[nsynctypes++] = RTWS_SYNC; + pr_info("%s: Testing normal GPs.\n", __func__); + } else if (gp_sync && !cur_ops->sync) { + pr_alert("%s: gp_sync without primitives.\n", __func__); + } + if (WARN_ONCE(nsynctypes == 0, + "rcu_torture_writer: No update-side primitives.\n")) { + /* + * No updates primitives, so don't try updating. + * The resulting test won't be testing much, hence the + * above WARN_ONCE(). + */ + rcu_torture_writer_state = RTWS_STOPPING; + torture_kthread_stopping("rcu_torture_writer"); + } + + do { + rcu_torture_writer_state = RTWS_FIXED_DELAY; + schedule_timeout_uninterruptible(1); + rp = rcu_torture_alloc(); + if (rp == NULL) + continue; + rp->rtort_pipe_count = 0; + rcu_torture_writer_state = RTWS_DELAY; + udelay(torture_random(&rand) & 0x3ff); + rcu_torture_writer_state = RTWS_REPLACE; + old_rp = rcu_dereference_check(rcu_torture_current, + current == writer_task); + rp->rtort_mbtest = 1; + rcu_assign_pointer(rcu_torture_current, rp); + smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */ + if (old_rp) { + i = old_rp->rtort_pipe_count; + if (i > RCU_TORTURE_PIPE_LEN) + i = RCU_TORTURE_PIPE_LEN; + atomic_inc(&rcu_torture_wcount[i]); + old_rp->rtort_pipe_count++; + switch (synctype[torture_random(&rand) % nsynctypes]) { + case RTWS_DEF_FREE: + rcu_torture_writer_state = RTWS_DEF_FREE; + cur_ops->deferred_free(old_rp); + break; + case RTWS_EXP_SYNC: + rcu_torture_writer_state = RTWS_EXP_SYNC; + cur_ops->exp_sync(); + rcu_torture_pipe_update(old_rp); + break; + case RTWS_COND_GET: + rcu_torture_writer_state = RTWS_COND_GET; + gp_snap = cur_ops->get_state(); + i = torture_random(&rand) % 16; + if (i != 0) + schedule_timeout_interruptible(i); + udelay(torture_random(&rand) % 1000); + rcu_torture_writer_state = RTWS_COND_SYNC; + cur_ops->cond_sync(gp_snap); + rcu_torture_pipe_update(old_rp); + break; + case RTWS_SYNC: + rcu_torture_writer_state = RTWS_SYNC; + cur_ops->sync(); + rcu_torture_pipe_update(old_rp); + break; + default: + WARN_ON_ONCE(1); + break; + } + } + rcu_torture_current_version++; + /* Cycle through nesting levels of rcu_expedite_gp() calls. */ + if (can_expedite && + !(torture_random(&rand) & 0xff & (!!expediting - 1))) { + WARN_ON_ONCE(expediting == 0 && rcu_gp_is_expedited()); + if (expediting >= 0) + rcu_expedite_gp(); + else + rcu_unexpedite_gp(); + if (++expediting > 3) + expediting = -expediting; + } else if (!can_expedite) { /* Disabled during boot, recheck. */ + can_expedite = !rcu_gp_is_expedited() && + !rcu_gp_is_normal(); + } + rcu_torture_writer_state = RTWS_STUTTER; + stutter_wait("rcu_torture_writer"); + } while (!torture_must_stop()); + /* Reset expediting back to unexpedited. */ + if (expediting > 0) + expediting = -expediting; + while (can_expedite && expediting++ < 0) + rcu_unexpedite_gp(); + WARN_ON_ONCE(can_expedite && rcu_gp_is_expedited()); + if (!can_expedite) + pr_alert("%s" TORTURE_FLAG + " Dynamic grace-period expediting was disabled.\n", + torture_type); + rcu_torture_writer_state = RTWS_STOPPING; + torture_kthread_stopping("rcu_torture_writer"); + return 0; +} + +/* + * RCU torture fake writer kthread. Repeatedly calls sync, with a random + * delay between calls. + */ +static int +rcu_torture_fakewriter(void *arg) +{ + DEFINE_TORTURE_RANDOM(rand); + + VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started"); + set_user_nice(current, MAX_NICE); + + do { + schedule_timeout_uninterruptible(1 + torture_random(&rand)%10); + udelay(torture_random(&rand) & 0x3ff); + if (cur_ops->cb_barrier != NULL && + torture_random(&rand) % (nfakewriters * 8) == 0) { + cur_ops->cb_barrier(); + } else if (gp_normal == gp_exp) { + if (cur_ops->sync && torture_random(&rand) & 0x80) + cur_ops->sync(); + else if (cur_ops->exp_sync) + cur_ops->exp_sync(); + } else if (gp_normal && cur_ops->sync) { + cur_ops->sync(); + } else if (cur_ops->exp_sync) { + cur_ops->exp_sync(); + } + stutter_wait("rcu_torture_fakewriter"); + } while (!torture_must_stop()); + + torture_kthread_stopping("rcu_torture_fakewriter"); + return 0; +} + +static void rcu_torture_timer_cb(struct rcu_head *rhp) +{ + kfree(rhp); +} + +/* + * Do one extension of an RCU read-side critical section using the + * current reader state in readstate (set to zero for initial entry + * to extended critical section), set the new state as specified by + * newstate (set to zero for final exit from extended critical section), + * and random-number-generator state in trsp. If this is neither the + * beginning or end of the critical section and if there was actually a + * change, do a ->read_delay(). + */ +static void rcutorture_one_extend(int *readstate, int newstate, + struct torture_random_state *trsp) +{ + int idxnew = -1; + int idxold = *readstate; + int statesnew = ~*readstate & newstate; + int statesold = *readstate & ~newstate; + + WARN_ON_ONCE(idxold < 0); + WARN_ON_ONCE((idxold >> RCUTORTURE_RDR_SHIFT) > 1); + + /* First, put new protection in place to avoid critical-section gap. */ + if (statesnew & RCUTORTURE_RDR_BH) + local_bh_disable(); + if (statesnew & RCUTORTURE_RDR_IRQ) + local_irq_disable(); + if (statesnew & RCUTORTURE_RDR_PREEMPT) + preempt_disable(); + if (statesnew & RCUTORTURE_RDR_RCU) + idxnew = cur_ops->readlock() << RCUTORTURE_RDR_SHIFT; + + /* Next, remove old protection, irq first due to bh conflict. */ + if (statesold & RCUTORTURE_RDR_IRQ) + local_irq_enable(); + if (statesold & RCUTORTURE_RDR_BH) + local_bh_enable(); + if (statesold & RCUTORTURE_RDR_PREEMPT) + preempt_enable(); + if (statesold & RCUTORTURE_RDR_RCU) + cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT); + + /* Delay if neither beginning nor end and there was a change. */ + if ((statesnew || statesold) && *readstate && newstate) + cur_ops->read_delay(trsp); + + /* Update the reader state. */ + if (idxnew == -1) + idxnew = idxold & ~RCUTORTURE_RDR_MASK; + WARN_ON_ONCE(idxnew < 0); + WARN_ON_ONCE((idxnew >> RCUTORTURE_RDR_SHIFT) > 1); + *readstate = idxnew | newstate; + WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) < 0); + WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) > 1); +} + +/* Return the biggest extendables mask given current RCU and boot parameters. */ +static int rcutorture_extend_mask_max(void) +{ + int mask; + + WARN_ON_ONCE(extendables & ~RCUTORTURE_MAX_EXTEND); + mask = extendables & RCUTORTURE_MAX_EXTEND & cur_ops->extendables; + mask = mask | RCUTORTURE_RDR_RCU; + return mask; +} + +/* Return a random protection state mask, but with at least one bit set. */ +static int +rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp) +{ + int mask = rcutorture_extend_mask_max(); + unsigned long randmask1 = torture_random(trsp) >> 8; + unsigned long randmask2 = randmask1 >> 1; + + WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT); + /* Half the time lots of bits, half the time only one bit. */ + if (randmask1 & 0x1) + mask = mask & randmask2; + else + mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS)); + if ((mask & RCUTORTURE_RDR_IRQ) && + !(mask & RCUTORTURE_RDR_BH) && + (oldmask & RCUTORTURE_RDR_BH)) + mask |= RCUTORTURE_RDR_BH; /* Can't enable bh w/irq disabled. */ + if ((mask & RCUTORTURE_RDR_IRQ) && + !(mask & cur_ops->ext_irq_conflict) && + (oldmask & cur_ops->ext_irq_conflict)) + mask |= cur_ops->ext_irq_conflict; /* Or if readers object. */ + return mask ?: RCUTORTURE_RDR_RCU; +} + +/* + * Do a randomly selected number of extensions of an existing RCU read-side + * critical section. + */ +static void rcutorture_loop_extend(int *readstate, + struct torture_random_state *trsp) +{ + int i; + int mask = rcutorture_extend_mask_max(); + + WARN_ON_ONCE(!*readstate); /* -Existing- RCU read-side critsect! */ + if (!((mask - 1) & mask)) + return; /* Current RCU flavor not extendable. */ + i = (torture_random(trsp) >> 3) & RCUTORTURE_RDR_MAX_LOOPS; + while (i--) { + mask = rcutorture_extend_mask(*readstate, trsp); + rcutorture_one_extend(readstate, mask, trsp); + } +} + +/* + * Do one read-side critical section, returning false if there was + * no data to read. Can be invoked both from process context and + * from a timer handler. + */ +static bool rcu_torture_one_read(struct torture_random_state *trsp) +{ + unsigned long started; + unsigned long completed; + int newstate; + struct rcu_torture *p; + int pipe_count; + int readstate = 0; + unsigned long long ts; + + newstate = rcutorture_extend_mask(readstate, trsp); + rcutorture_one_extend(&readstate, newstate, trsp); + started = cur_ops->get_gp_seq(); + ts = rcu_trace_clock_local(); + p = rcu_dereference_check(rcu_torture_current, + rcu_read_lock_bh_held() || + rcu_read_lock_sched_held() || + srcu_read_lock_held(srcu_ctlp) || + torturing_tasks()); + if (p == NULL) { + /* Wait for rcu_torture_writer to get underway */ + rcutorture_one_extend(&readstate, 0, trsp); + return false; + } + if (p->rtort_mbtest == 0) + atomic_inc(&n_rcu_torture_mberror); + rcutorture_loop_extend(&readstate, trsp); + preempt_disable(); + pipe_count = p->rtort_pipe_count; + if (pipe_count > RCU_TORTURE_PIPE_LEN) { + /* Should not happen, but... */ + pipe_count = RCU_TORTURE_PIPE_LEN; + } + completed = cur_ops->get_gp_seq(); + if (pipe_count > 1) { + do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, + ts, started, completed); + rcu_ftrace_dump(DUMP_ALL); + } + __this_cpu_inc(rcu_torture_count[pipe_count]); + completed = rcutorture_seq_diff(completed, started); + if (completed > RCU_TORTURE_PIPE_LEN) { + /* Should not happen, but... */ + completed = RCU_TORTURE_PIPE_LEN; + } + __this_cpu_inc(rcu_torture_batch[completed]); + preempt_enable(); + rcutorture_one_extend(&readstate, 0, trsp); + WARN_ON_ONCE(readstate & RCUTORTURE_RDR_MASK); + return true; +} + +static DEFINE_TORTURE_RANDOM_PERCPU(rcu_torture_timer_rand); + +/* + * RCU torture reader from timer handler. Dereferences rcu_torture_current, + * incrementing the corresponding element of the pipeline array. The + * counter in the element should never be greater than 1, otherwise, the + * RCU implementation is broken. + */ +static void rcu_torture_timer(struct timer_list *unused) +{ + atomic_long_inc(&n_rcu_torture_timers); + (void)rcu_torture_one_read(this_cpu_ptr(&rcu_torture_timer_rand)); + + /* Test call_rcu() invocation from interrupt handler. */ + if (cur_ops->call) { + struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_NOWAIT); + + if (rhp) + cur_ops->call(rhp, rcu_torture_timer_cb); + } +} + +/* + * RCU torture reader kthread. Repeatedly dereferences rcu_torture_current, + * incrementing the corresponding element of the pipeline array. The + * counter in the element should never be greater than 1, otherwise, the + * RCU implementation is broken. + */ +static int +rcu_torture_reader(void *arg) +{ + DEFINE_TORTURE_RANDOM(rand); + struct timer_list t; + + VERBOSE_TOROUT_STRING("rcu_torture_reader task started"); + set_user_nice(current, MAX_NICE); + if (irqreader && cur_ops->irq_capable) + timer_setup_on_stack(&t, rcu_torture_timer, 0); + + do { + if (irqreader && cur_ops->irq_capable) { + if (!timer_pending(&t)) + mod_timer(&t, jiffies + 1); + } + if (!rcu_torture_one_read(&rand)) + schedule_timeout_interruptible(HZ); + stutter_wait("rcu_torture_reader"); + } while (!torture_must_stop()); + if (irqreader && cur_ops->irq_capable) { + del_timer_sync(&t); + destroy_timer_on_stack(&t); + } + torture_kthread_stopping("rcu_torture_reader"); + return 0; +} + +/* + * Print torture statistics. Caller must ensure that there is only + * one call to this function at a given time!!! This is normally + * accomplished by relying on the module system to only have one copy + * of the module loaded, and then by giving the rcu_torture_stats + * kthread full control (or the init/cleanup functions when rcu_torture_stats + * thread is not running). + */ +static void +rcu_torture_stats_print(void) +{ + int cpu; + int i; + long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 }; + long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 }; + static unsigned long rtcv_snap = ULONG_MAX; + static bool splatted; + struct task_struct *wtp; + + for_each_possible_cpu(cpu) { + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) { + pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i]; + batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i]; + } + } + for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) { + if (pipesummary[i] != 0) + break; + } + + pr_alert("%s%s ", torture_type, TORTURE_FLAG); + pr_cont("rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d ", + rcu_torture_current, + rcu_torture_current_version, + list_empty(&rcu_torture_freelist), + atomic_read(&n_rcu_torture_alloc), + atomic_read(&n_rcu_torture_alloc_fail), + atomic_read(&n_rcu_torture_free)); + pr_cont("rtmbe: %d rtbe: %ld rtbke: %ld rtbre: %ld ", + atomic_read(&n_rcu_torture_mberror), + n_rcu_torture_barrier_error, + n_rcu_torture_boost_ktrerror, + n_rcu_torture_boost_rterror); + pr_cont("rtbf: %ld rtb: %ld nt: %ld ", + n_rcu_torture_boost_failure, + n_rcu_torture_boosts, + atomic_long_read(&n_rcu_torture_timers)); + torture_onoff_stats(); + pr_cont("barrier: %ld/%ld:%ld ", + n_barrier_successes, + n_barrier_attempts, + n_rcu_torture_barrier_error); + pr_cont("cbflood: %ld\n", atomic_long_read(&n_cbfloods)); + + pr_alert("%s%s ", torture_type, TORTURE_FLAG); + if (atomic_read(&n_rcu_torture_mberror) != 0 || + n_rcu_torture_barrier_error != 0 || + n_rcu_torture_boost_ktrerror != 0 || + n_rcu_torture_boost_rterror != 0 || + n_rcu_torture_boost_failure != 0 || + i > 1) { + pr_cont("%s", "!!! "); + atomic_inc(&n_rcu_torture_error); + WARN_ON_ONCE(1); + } + pr_cont("Reader Pipe: "); + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) + pr_cont(" %ld", pipesummary[i]); + pr_cont("\n"); + + pr_alert("%s%s ", torture_type, TORTURE_FLAG); + pr_cont("Reader Batch: "); + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) + pr_cont(" %ld", batchsummary[i]); + pr_cont("\n"); + + pr_alert("%s%s ", torture_type, TORTURE_FLAG); + pr_cont("Free-Block Circulation: "); + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) { + pr_cont(" %d", atomic_read(&rcu_torture_wcount[i])); + } + pr_cont("\n"); + + if (cur_ops->stats) + cur_ops->stats(); + if (rtcv_snap == rcu_torture_current_version && + rcu_torture_current != NULL) { + int __maybe_unused flags = 0; + unsigned long __maybe_unused gp_seq = 0; + + rcutorture_get_gp_data(cur_ops->ttype, + &flags, &gp_seq); + srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, + &flags, &gp_seq); + wtp = READ_ONCE(writer_task); + pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#lx cpu %d\n", + rcu_torture_writer_state_getname(), + rcu_torture_writer_state, gp_seq, flags, + wtp == NULL ? ~0UL : wtp->state, + wtp == NULL ? -1 : (int)task_cpu(wtp)); + if (!splatted && wtp) { + sched_show_task(wtp); + splatted = true; + } + show_rcu_gp_kthreads(); + rcu_ftrace_dump(DUMP_ALL); + } + rtcv_snap = rcu_torture_current_version; +} + +/* + * Periodically prints torture statistics, if periodic statistics printing + * was specified via the stat_interval module parameter. + */ +static int +rcu_torture_stats(void *arg) +{ + VERBOSE_TOROUT_STRING("rcu_torture_stats task started"); + do { + schedule_timeout_interruptible(stat_interval * HZ); + rcu_torture_stats_print(); + torture_shutdown_absorb("rcu_torture_stats"); + } while (!torture_must_stop()); + torture_kthread_stopping("rcu_torture_stats"); + return 0; +} + +static void +rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag) +{ + pr_alert("%s" TORTURE_FLAG + "--- %s: nreaders=%d nfakewriters=%d " + "stat_interval=%d verbose=%d test_no_idle_hz=%d " + "shuffle_interval=%d stutter=%d irqreader=%d " + "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d " + "test_boost=%d/%d test_boost_interval=%d " + "test_boost_duration=%d shutdown_secs=%d " + "stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d " + "n_barrier_cbs=%d " + "onoff_interval=%d onoff_holdoff=%d\n", + torture_type, tag, nrealreaders, nfakewriters, + stat_interval, verbose, test_no_idle_hz, shuffle_interval, + stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter, + test_boost, cur_ops->can_boost, + test_boost_interval, test_boost_duration, shutdown_secs, + stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff, + n_barrier_cbs, + onoff_interval, onoff_holdoff); +} + +static int rcutorture_booster_cleanup(unsigned int cpu) +{ + struct task_struct *t; + + if (boost_tasks[cpu] == NULL) + return 0; + mutex_lock(&boost_mutex); + t = boost_tasks[cpu]; + boost_tasks[cpu] = NULL; + rcu_torture_enable_rt_throttle(); + mutex_unlock(&boost_mutex); + + /* This must be outside of the mutex, otherwise deadlock! */ + torture_stop_kthread(rcu_torture_boost, t); + return 0; +} + +static int rcutorture_booster_init(unsigned int cpu) +{ + int retval; + + if (boost_tasks[cpu] != NULL) + return 0; /* Already created, nothing more to do. */ + + /* Don't allow time recalculation while creating a new task. */ + mutex_lock(&boost_mutex); + rcu_torture_disable_rt_throttle(); + VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task"); + boost_tasks[cpu] = kthread_create_on_node(rcu_torture_boost, NULL, + cpu_to_node(cpu), + "rcu_torture_boost"); + if (IS_ERR(boost_tasks[cpu])) { + retval = PTR_ERR(boost_tasks[cpu]); + VERBOSE_TOROUT_STRING("rcu_torture_boost task create failed"); + n_rcu_torture_boost_ktrerror++; + boost_tasks[cpu] = NULL; + mutex_unlock(&boost_mutex); + return retval; + } + kthread_bind(boost_tasks[cpu], cpu); + wake_up_process(boost_tasks[cpu]); + mutex_unlock(&boost_mutex); + return 0; +} + +/* + * CPU-stall kthread. It waits as specified by stall_cpu_holdoff, then + * induces a CPU stall for the time specified by stall_cpu. + */ +static int rcu_torture_stall(void *args) +{ + unsigned long stop_at; + + VERBOSE_TOROUT_STRING("rcu_torture_stall task started"); + if (stall_cpu_holdoff > 0) { + VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff"); + schedule_timeout_interruptible(stall_cpu_holdoff * HZ); + VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff"); + } + if (!kthread_should_stop()) { + stop_at = ktime_get_seconds() + stall_cpu; + /* RCU CPU stall is expected behavior in following code. */ + rcu_read_lock(); + if (stall_cpu_irqsoff) + local_irq_disable(); + else + preempt_disable(); + pr_alert("rcu_torture_stall start on CPU %d.\n", + smp_processor_id()); + while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(), + stop_at)) + continue; /* Induce RCU CPU stall warning. */ + if (stall_cpu_irqsoff) + local_irq_enable(); + else + preempt_enable(); + rcu_read_unlock(); + pr_alert("rcu_torture_stall end.\n"); + } + torture_shutdown_absorb("rcu_torture_stall"); + while (!kthread_should_stop()) + schedule_timeout_interruptible(10 * HZ); + return 0; +} + +/* Spawn CPU-stall kthread, if stall_cpu specified. */ +static int __init rcu_torture_stall_init(void) +{ + if (stall_cpu <= 0) + return 0; + return torture_create_kthread(rcu_torture_stall, NULL, stall_task); +} + +/* Callback function for RCU barrier testing. */ +static void rcu_torture_barrier_cbf(struct rcu_head *rcu) +{ + atomic_inc(&barrier_cbs_invoked); +} + +/* kthread function to register callbacks used to test RCU barriers. */ +static int rcu_torture_barrier_cbs(void *arg) +{ + long myid = (long)arg; + bool lastphase = 0; + bool newphase; + struct rcu_head rcu; + + init_rcu_head_on_stack(&rcu); + VERBOSE_TOROUT_STRING("rcu_torture_barrier_cbs task started"); + set_user_nice(current, MAX_NICE); + do { + wait_event(barrier_cbs_wq[myid], + (newphase = + smp_load_acquire(&barrier_phase)) != lastphase || + torture_must_stop()); + lastphase = newphase; + if (torture_must_stop()) + break; + /* + * The above smp_load_acquire() ensures barrier_phase load + * is ordered before the following ->call(). + */ + local_irq_disable(); /* Just to test no-irq call_rcu(). */ + cur_ops->call(&rcu, rcu_torture_barrier_cbf); + local_irq_enable(); + if (atomic_dec_and_test(&barrier_cbs_count)) + wake_up(&barrier_wq); + } while (!torture_must_stop()); + if (cur_ops->cb_barrier != NULL) + cur_ops->cb_barrier(); + destroy_rcu_head_on_stack(&rcu); + torture_kthread_stopping("rcu_torture_barrier_cbs"); + return 0; +} + +/* kthread function to drive and coordinate RCU barrier testing. */ +static int rcu_torture_barrier(void *arg) +{ + int i; + + VERBOSE_TOROUT_STRING("rcu_torture_barrier task starting"); + do { + atomic_set(&barrier_cbs_invoked, 0); + atomic_set(&barrier_cbs_count, n_barrier_cbs); + /* Ensure barrier_phase ordered after prior assignments. */ + smp_store_release(&barrier_phase, !barrier_phase); + for (i = 0; i < n_barrier_cbs; i++) + wake_up(&barrier_cbs_wq[i]); + wait_event(barrier_wq, + atomic_read(&barrier_cbs_count) == 0 || + torture_must_stop()); + if (torture_must_stop()) + break; + n_barrier_attempts++; + cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */ + if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) { + n_rcu_torture_barrier_error++; + pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n", + atomic_read(&barrier_cbs_invoked), + n_barrier_cbs); + WARN_ON_ONCE(1); + } else { + n_barrier_successes++; + } + schedule_timeout_interruptible(HZ / 10); + } while (!torture_must_stop()); + torture_kthread_stopping("rcu_torture_barrier"); + return 0; +} + +/* Initialize RCU barrier testing. */ +static int rcu_torture_barrier_init(void) +{ + int i; + int ret; + + if (n_barrier_cbs <= 0) + return 0; + if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) { + pr_alert("%s" TORTURE_FLAG + " Call or barrier ops missing for %s,\n", + torture_type, cur_ops->name); + pr_alert("%s" TORTURE_FLAG + " RCU barrier testing omitted from run.\n", + torture_type); + return 0; + } + atomic_set(&barrier_cbs_count, 0); + atomic_set(&barrier_cbs_invoked, 0); + barrier_cbs_tasks = + kcalloc(n_barrier_cbs, sizeof(barrier_cbs_tasks[0]), + GFP_KERNEL); + barrier_cbs_wq = + kcalloc(n_barrier_cbs, sizeof(barrier_cbs_wq[0]), GFP_KERNEL); + if (barrier_cbs_tasks == NULL || !barrier_cbs_wq) + return -ENOMEM; + for (i = 0; i < n_barrier_cbs; i++) { + init_waitqueue_head(&barrier_cbs_wq[i]); + ret = torture_create_kthread(rcu_torture_barrier_cbs, + (void *)(long)i, + barrier_cbs_tasks[i]); + if (ret) + return ret; + } + return torture_create_kthread(rcu_torture_barrier, NULL, barrier_task); +} + +/* Clean up after RCU barrier testing. */ +static void rcu_torture_barrier_cleanup(void) +{ + int i; + + torture_stop_kthread(rcu_torture_barrier, barrier_task); + if (barrier_cbs_tasks != NULL) { + for (i = 0; i < n_barrier_cbs; i++) + torture_stop_kthread(rcu_torture_barrier_cbs, + barrier_cbs_tasks[i]); + kfree(barrier_cbs_tasks); + barrier_cbs_tasks = NULL; + } + if (barrier_cbs_wq != NULL) { + kfree(barrier_cbs_wq); + barrier_cbs_wq = NULL; + } +} + +static bool rcu_torture_can_boost(void) +{ + static int boost_warn_once; + int prio; + + if (!(test_boost == 1 && cur_ops->can_boost) && test_boost != 2) + return false; + + prio = rcu_get_gp_kthreads_prio(); + if (!prio) + return false; + + if (prio < 2) { + if (boost_warn_once == 1) + return false; + + pr_alert("%s: WARN: RCU kthread priority too low to test boosting. Skipping RCU boost test. Try passing rcutree.kthread_prio > 1 on the kernel command line.\n", KBUILD_MODNAME); + boost_warn_once = 1; + return false; + } + + return true; +} + +static enum cpuhp_state rcutor_hp; + +static void +rcu_torture_cleanup(void) +{ + int flags = 0; + unsigned long gp_seq = 0; + int i; + + if (torture_cleanup_begin()) { + if (cur_ops->cb_barrier != NULL) + cur_ops->cb_barrier(); + return; + } + if (!cur_ops) { + torture_cleanup_end(); + return; + } + + rcu_torture_barrier_cleanup(); + torture_stop_kthread(rcu_torture_stall, stall_task); + torture_stop_kthread(rcu_torture_writer, writer_task); + + if (reader_tasks) { + for (i = 0; i < nrealreaders; i++) + torture_stop_kthread(rcu_torture_reader, + reader_tasks[i]); + kfree(reader_tasks); + } + rcu_torture_current = NULL; + + if (fakewriter_tasks) { + for (i = 0; i < nfakewriters; i++) { + torture_stop_kthread(rcu_torture_fakewriter, + fakewriter_tasks[i]); + } + kfree(fakewriter_tasks); + fakewriter_tasks = NULL; + } + + rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq); + srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq); + pr_alert("%s: End-test grace-period state: g%lu f%#x\n", + cur_ops->name, gp_seq, flags); + torture_stop_kthread(rcu_torture_stats, stats_task); + torture_stop_kthread(rcu_torture_fqs, fqs_task); + for (i = 0; i < ncbflooders; i++) + torture_stop_kthread(rcu_torture_cbflood, cbflood_task[i]); + if (rcu_torture_can_boost()) + cpuhp_remove_state(rcutor_hp); + + /* + * Wait for all RCU callbacks to fire, then do flavor-specific + * cleanup operations. + */ + if (cur_ops->cb_barrier != NULL) + cur_ops->cb_barrier(); + if (cur_ops->cleanup != NULL) + cur_ops->cleanup(); + + rcu_torture_stats_print(); /* -After- the stats thread is stopped! */ + + if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error) + rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE"); + else if (torture_onoff_failures()) + rcu_torture_print_module_parms(cur_ops, + "End of test: RCU_HOTPLUG"); + else + rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS"); + torture_cleanup_end(); +} + +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD +static void rcu_torture_leak_cb(struct rcu_head *rhp) +{ +} + +static void rcu_torture_err_cb(struct rcu_head *rhp) +{ + /* + * This -might- happen due to race conditions, but is unlikely. + * The scenario that leads to this happening is that the + * first of the pair of duplicate callbacks is queued, + * someone else starts a grace period that includes that + * callback, then the second of the pair must wait for the + * next grace period. Unlikely, but can happen. If it + * does happen, the debug-objects subsystem won't have splatted. + */ + pr_alert("%s: duplicated callback was invoked.\n", KBUILD_MODNAME); +} +#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ + +/* + * Verify that double-free causes debug-objects to complain, but only + * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y. Otherwise, say that the test + * cannot be carried out. + */ +static void rcu_test_debug_objects(void) +{ +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD + struct rcu_head rh1; + struct rcu_head rh2; + + init_rcu_head_on_stack(&rh1); + init_rcu_head_on_stack(&rh2); + pr_alert("%s: WARN: Duplicate call_rcu() test starting.\n", KBUILD_MODNAME); + + /* Try to queue the rh2 pair of callbacks for the same grace period. */ + preempt_disable(); /* Prevent preemption from interrupting test. */ + rcu_read_lock(); /* Make it impossible to finish a grace period. */ + call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */ + local_irq_disable(); /* Make it harder to start a new grace period. */ + call_rcu(&rh2, rcu_torture_leak_cb); + call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */ + local_irq_enable(); + rcu_read_unlock(); + preempt_enable(); + + /* Wait for them all to get done so we can safely return. */ + rcu_barrier(); + pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME); + destroy_rcu_head_on_stack(&rh1); + destroy_rcu_head_on_stack(&rh2); +#else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ + pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME); +#endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ +} + +static int __init +rcu_torture_init(void) +{ + int i; + int cpu; + int firsterr = 0; + static struct rcu_torture_ops *torture_ops[] = { + &rcu_ops, &rcu_bh_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops, + &busted_srcud_ops, &sched_ops, &tasks_ops, + }; + + if (!torture_init_begin(torture_type, verbose)) + return -EBUSY; + + /* Process args and tell the world that the torturer is on the job. */ + for (i = 0; i < ARRAY_SIZE(torture_ops); i++) { + cur_ops = torture_ops[i]; + if (strcmp(torture_type, cur_ops->name) == 0) + break; + } + if (i == ARRAY_SIZE(torture_ops)) { + pr_alert("rcu-torture: invalid torture type: \"%s\"\n", + torture_type); + pr_alert("rcu-torture types:"); + for (i = 0; i < ARRAY_SIZE(torture_ops); i++) + pr_cont(" %s", torture_ops[i]->name); + pr_cont("\n"); + firsterr = -EINVAL; + cur_ops = NULL; + goto unwind; + } + if (cur_ops->fqs == NULL && fqs_duration != 0) { + pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n"); + fqs_duration = 0; + } + if (cur_ops->init) + cur_ops->init(); + + if (nreaders >= 0) { + nrealreaders = nreaders; + } else { + nrealreaders = num_online_cpus() - 2 - nreaders; + if (nrealreaders <= 0) + nrealreaders = 1; + } + rcu_torture_print_module_parms(cur_ops, "Start of test"); + + /* Set up the freelist. */ + + INIT_LIST_HEAD(&rcu_torture_freelist); + for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) { + rcu_tortures[i].rtort_mbtest = 0; + list_add_tail(&rcu_tortures[i].rtort_free, + &rcu_torture_freelist); + } + + /* Initialize the statistics so that each run gets its own numbers. */ + + rcu_torture_current = NULL; + rcu_torture_current_version = 0; + atomic_set(&n_rcu_torture_alloc, 0); + atomic_set(&n_rcu_torture_alloc_fail, 0); + atomic_set(&n_rcu_torture_free, 0); + atomic_set(&n_rcu_torture_mberror, 0); + atomic_set(&n_rcu_torture_error, 0); + n_rcu_torture_barrier_error = 0; + n_rcu_torture_boost_ktrerror = 0; + n_rcu_torture_boost_rterror = 0; + n_rcu_torture_boost_failure = 0; + n_rcu_torture_boosts = 0; + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) + atomic_set(&rcu_torture_wcount[i], 0); + for_each_possible_cpu(cpu) { + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) { + per_cpu(rcu_torture_count, cpu)[i] = 0; + per_cpu(rcu_torture_batch, cpu)[i] = 0; + } + } + + /* Start up the kthreads. */ + + firsterr = torture_create_kthread(rcu_torture_writer, NULL, + writer_task); + if (firsterr) + goto unwind; + if (nfakewriters > 0) { + fakewriter_tasks = kcalloc(nfakewriters, + sizeof(fakewriter_tasks[0]), + GFP_KERNEL); + if (fakewriter_tasks == NULL) { + VERBOSE_TOROUT_ERRSTRING("out of memory"); + firsterr = -ENOMEM; + goto unwind; + } + } + for (i = 0; i < nfakewriters; i++) { + firsterr = torture_create_kthread(rcu_torture_fakewriter, + NULL, fakewriter_tasks[i]); + if (firsterr) + goto unwind; + } + reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]), + GFP_KERNEL); + if (reader_tasks == NULL) { + VERBOSE_TOROUT_ERRSTRING("out of memory"); + firsterr = -ENOMEM; + goto unwind; + } + for (i = 0; i < nrealreaders; i++) { + firsterr = torture_create_kthread(rcu_torture_reader, NULL, + reader_tasks[i]); + if (firsterr) + goto unwind; + } + if (stat_interval > 0) { + firsterr = torture_create_kthread(rcu_torture_stats, NULL, + stats_task); + if (firsterr) + goto unwind; + } + if (test_no_idle_hz && shuffle_interval > 0) { + firsterr = torture_shuffle_init(shuffle_interval * HZ); + if (firsterr) + goto unwind; + } + if (stutter < 0) + stutter = 0; + if (stutter) { + firsterr = torture_stutter_init(stutter * HZ); + if (firsterr) + goto unwind; + } + if (fqs_duration < 0) + fqs_duration = 0; + if (fqs_duration) { + /* Create the fqs thread */ + firsterr = torture_create_kthread(rcu_torture_fqs, NULL, + fqs_task); + if (firsterr) + goto unwind; + } + if (test_boost_interval < 1) + test_boost_interval = 1; + if (test_boost_duration < 2) + test_boost_duration = 2; + if (rcu_torture_can_boost()) { + + boost_starttime = jiffies + test_boost_interval * HZ; + + firsterr = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "RCU_TORTURE", + rcutorture_booster_init, + rcutorture_booster_cleanup); + if (firsterr < 0) + goto unwind; + rcutor_hp = firsterr; + } + firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup); + if (firsterr) + goto unwind; + firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval); + if (firsterr) + goto unwind; + firsterr = rcu_torture_stall_init(); + if (firsterr) + goto unwind; + firsterr = rcu_torture_barrier_init(); + if (firsterr) + goto unwind; + if (object_debug) + rcu_test_debug_objects(); + if (cbflood_n_burst > 0) { + /* Create the cbflood threads */ + ncbflooders = (num_online_cpus() + 3) / 4; + cbflood_task = kcalloc(ncbflooders, sizeof(*cbflood_task), + GFP_KERNEL); + if (!cbflood_task) { + VERBOSE_TOROUT_ERRSTRING("out of memory"); + firsterr = -ENOMEM; + goto unwind; + } + for (i = 0; i < ncbflooders; i++) { + firsterr = torture_create_kthread(rcu_torture_cbflood, + NULL, + cbflood_task[i]); + if (firsterr) + goto unwind; + } + } + torture_init_end(); + return 0; + +unwind: + torture_init_end(); + rcu_torture_cleanup(); + return firsterr; +} + +module_init(rcu_torture_init); +module_exit(rcu_torture_cleanup); diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c new file mode 100644 index 000000000..04fc2ed71 --- /dev/null +++ b/kernel/rcu/srcutiny.c @@ -0,0 +1,206 @@ +/* + * Sleepable Read-Copy Update mechanism for mutual exclusion, + * tiny version for non-preemptible single-CPU use. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright (C) IBM Corporation, 2017 + * + * Author: Paul McKenney <paulmck@us.ibm.com> + */ + +#include <linux/export.h> +#include <linux/mutex.h> +#include <linux/preempt.h> +#include <linux/rcupdate_wait.h> +#include <linux/sched.h> +#include <linux/delay.h> +#include <linux/srcu.h> + +#include <linux/rcu_node_tree.h> +#include "rcu_segcblist.h" +#include "rcu.h" + +int rcu_scheduler_active __read_mostly; + +static int init_srcu_struct_fields(struct srcu_struct *sp) +{ + sp->srcu_lock_nesting[0] = 0; + sp->srcu_lock_nesting[1] = 0; + init_swait_queue_head(&sp->srcu_wq); + sp->srcu_cb_head = NULL; + sp->srcu_cb_tail = &sp->srcu_cb_head; + sp->srcu_gp_running = false; + sp->srcu_gp_waiting = false; + sp->srcu_idx = 0; + INIT_WORK(&sp->srcu_work, srcu_drive_gp); + return 0; +} + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +int __init_srcu_struct(struct srcu_struct *sp, const char *name, + struct lock_class_key *key) +{ + /* Don't re-initialize a lock while it is held. */ + debug_check_no_locks_freed((void *)sp, sizeof(*sp)); + lockdep_init_map(&sp->dep_map, name, key, 0); + return init_srcu_struct_fields(sp); +} +EXPORT_SYMBOL_GPL(__init_srcu_struct); + +#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +/* + * init_srcu_struct - initialize a sleep-RCU structure + * @sp: structure to initialize. + * + * Must invoke this on a given srcu_struct before passing that srcu_struct + * to any other function. Each srcu_struct represents a separate domain + * of SRCU protection. + */ +int init_srcu_struct(struct srcu_struct *sp) +{ + return init_srcu_struct_fields(sp); +} +EXPORT_SYMBOL_GPL(init_srcu_struct); + +#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +/* + * cleanup_srcu_struct - deconstruct a sleep-RCU structure + * @sp: structure to clean up. + * + * Must invoke this after you are finished using a given srcu_struct that + * was initialized via init_srcu_struct(), else you leak memory. + */ +void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced) +{ + WARN_ON(sp->srcu_lock_nesting[0] || sp->srcu_lock_nesting[1]); + if (quiesced) + WARN_ON(work_pending(&sp->srcu_work)); + else + flush_work(&sp->srcu_work); + WARN_ON(sp->srcu_gp_running); + WARN_ON(sp->srcu_gp_waiting); + WARN_ON(sp->srcu_cb_head); + WARN_ON(&sp->srcu_cb_head != sp->srcu_cb_tail); +} +EXPORT_SYMBOL_GPL(_cleanup_srcu_struct); + +/* + * Removes the count for the old reader from the appropriate element of + * the srcu_struct. + */ +void __srcu_read_unlock(struct srcu_struct *sp, int idx) +{ + int newval = sp->srcu_lock_nesting[idx] - 1; + + WRITE_ONCE(sp->srcu_lock_nesting[idx], newval); + if (!newval && READ_ONCE(sp->srcu_gp_waiting)) + swake_up_one(&sp->srcu_wq); +} +EXPORT_SYMBOL_GPL(__srcu_read_unlock); + +/* + * Workqueue handler to drive one grace period and invoke any callbacks + * that become ready as a result. Single-CPU and !PREEMPT operation + * means that we get away with murder on synchronization. ;-) + */ +void srcu_drive_gp(struct work_struct *wp) +{ + int idx; + struct rcu_head *lh; + struct rcu_head *rhp; + struct srcu_struct *sp; + + sp = container_of(wp, struct srcu_struct, srcu_work); + if (sp->srcu_gp_running || !READ_ONCE(sp->srcu_cb_head)) + return; /* Already running or nothing to do. */ + + /* Remove recently arrived callbacks and wait for readers. */ + WRITE_ONCE(sp->srcu_gp_running, true); + local_irq_disable(); + lh = sp->srcu_cb_head; + sp->srcu_cb_head = NULL; + sp->srcu_cb_tail = &sp->srcu_cb_head; + local_irq_enable(); + idx = sp->srcu_idx; + WRITE_ONCE(sp->srcu_idx, !sp->srcu_idx); + WRITE_ONCE(sp->srcu_gp_waiting, true); /* srcu_read_unlock() wakes! */ + swait_event_exclusive(sp->srcu_wq, !READ_ONCE(sp->srcu_lock_nesting[idx])); + WRITE_ONCE(sp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */ + + /* Invoke the callbacks we removed above. */ + while (lh) { + rhp = lh; + lh = lh->next; + local_bh_disable(); + rhp->func(rhp); + local_bh_enable(); + } + + /* + * Enable rescheduling, and if there are more callbacks, + * reschedule ourselves. This can race with a call_srcu() + * at interrupt level, but the ->srcu_gp_running checks will + * straighten that out. + */ + WRITE_ONCE(sp->srcu_gp_running, false); + if (READ_ONCE(sp->srcu_cb_head)) + schedule_work(&sp->srcu_work); +} +EXPORT_SYMBOL_GPL(srcu_drive_gp); + +/* + * Enqueue an SRCU callback on the specified srcu_struct structure, + * initiating grace-period processing if it is not already running. + */ +void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, + rcu_callback_t func) +{ + unsigned long flags; + + rhp->func = func; + rhp->next = NULL; + local_irq_save(flags); + *sp->srcu_cb_tail = rhp; + sp->srcu_cb_tail = &rhp->next; + local_irq_restore(flags); + if (!READ_ONCE(sp->srcu_gp_running)) + schedule_work(&sp->srcu_work); +} +EXPORT_SYMBOL_GPL(call_srcu); + +/* + * synchronize_srcu - wait for prior SRCU read-side critical-section completion + */ +void synchronize_srcu(struct srcu_struct *sp) +{ + struct rcu_synchronize rs; + + init_rcu_head_on_stack(&rs.head); + init_completion(&rs.completion); + call_srcu(sp, &rs.head, wakeme_after_rcu); + wait_for_completion(&rs.completion); + destroy_rcu_head_on_stack(&rs.head); +} +EXPORT_SYMBOL_GPL(synchronize_srcu); + +/* Lockdep diagnostics. */ +void __init rcu_scheduler_starting(void) +{ + rcu_scheduler_active = RCU_SCHEDULER_RUNNING; +} diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c new file mode 100644 index 000000000..1ff17e297 --- /dev/null +++ b/kernel/rcu/srcutree.c @@ -0,0 +1,1312 @@ +/* + * Sleepable Read-Copy Update mechanism for mutual exclusion. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright (C) IBM Corporation, 2006 + * Copyright (C) Fujitsu, 2012 + * + * Author: Paul McKenney <paulmck@us.ibm.com> + * Lai Jiangshan <laijs@cn.fujitsu.com> + * + * For detailed explanation of Read-Copy Update mechanism see - + * Documentation/RCU/ *.txt + * + */ + +#define pr_fmt(fmt) "rcu: " fmt + +#include <linux/export.h> +#include <linux/mutex.h> +#include <linux/percpu.h> +#include <linux/preempt.h> +#include <linux/rcupdate_wait.h> +#include <linux/sched.h> +#include <linux/smp.h> +#include <linux/delay.h> +#include <linux/module.h> +#include <linux/srcu.h> + +#include "rcu.h" +#include "rcu_segcblist.h" + +/* Holdoff in nanoseconds for auto-expediting. */ +#define DEFAULT_SRCU_EXP_HOLDOFF (25 * 1000) +static ulong exp_holdoff = DEFAULT_SRCU_EXP_HOLDOFF; +module_param(exp_holdoff, ulong, 0444); + +/* Overflow-check frequency. N bits roughly says every 2**N grace periods. */ +static ulong counter_wrap_check = (ULONG_MAX >> 2); +module_param(counter_wrap_check, ulong, 0444); + +static void srcu_invoke_callbacks(struct work_struct *work); +static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay); +static void process_srcu(struct work_struct *work); + +/* Wrappers for lock acquisition and release, see raw_spin_lock_rcu_node(). */ +#define spin_lock_rcu_node(p) \ +do { \ + spin_lock(&ACCESS_PRIVATE(p, lock)); \ + smp_mb__after_unlock_lock(); \ +} while (0) + +#define spin_unlock_rcu_node(p) spin_unlock(&ACCESS_PRIVATE(p, lock)) + +#define spin_lock_irq_rcu_node(p) \ +do { \ + spin_lock_irq(&ACCESS_PRIVATE(p, lock)); \ + smp_mb__after_unlock_lock(); \ +} while (0) + +#define spin_unlock_irq_rcu_node(p) \ + spin_unlock_irq(&ACCESS_PRIVATE(p, lock)) + +#define spin_lock_irqsave_rcu_node(p, flags) \ +do { \ + spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \ + smp_mb__after_unlock_lock(); \ +} while (0) + +#define spin_unlock_irqrestore_rcu_node(p, flags) \ + spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags) \ + +/* + * Initialize SRCU combining tree. Note that statically allocated + * srcu_struct structures might already have srcu_read_lock() and + * srcu_read_unlock() running against them. So if the is_static parameter + * is set, don't initialize ->srcu_lock_count[] and ->srcu_unlock_count[]. + */ +static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static) +{ + int cpu; + int i; + int level = 0; + int levelspread[RCU_NUM_LVLS]; + struct srcu_data *sdp; + struct srcu_node *snp; + struct srcu_node *snp_first; + + /* Work out the overall tree geometry. */ + sp->level[0] = &sp->node[0]; + for (i = 1; i < rcu_num_lvls; i++) + sp->level[i] = sp->level[i - 1] + num_rcu_lvl[i - 1]; + rcu_init_levelspread(levelspread, num_rcu_lvl); + + /* Each pass through this loop initializes one srcu_node structure. */ + rcu_for_each_node_breadth_first(sp, snp) { + spin_lock_init(&ACCESS_PRIVATE(snp, lock)); + WARN_ON_ONCE(ARRAY_SIZE(snp->srcu_have_cbs) != + ARRAY_SIZE(snp->srcu_data_have_cbs)); + for (i = 0; i < ARRAY_SIZE(snp->srcu_have_cbs); i++) { + snp->srcu_have_cbs[i] = 0; + snp->srcu_data_have_cbs[i] = 0; + } + snp->srcu_gp_seq_needed_exp = 0; + snp->grplo = -1; + snp->grphi = -1; + if (snp == &sp->node[0]) { + /* Root node, special case. */ + snp->srcu_parent = NULL; + continue; + } + + /* Non-root node. */ + if (snp == sp->level[level + 1]) + level++; + snp->srcu_parent = sp->level[level - 1] + + (snp - sp->level[level]) / + levelspread[level - 1]; + } + + /* + * Initialize the per-CPU srcu_data array, which feeds into the + * leaves of the srcu_node tree. + */ + WARN_ON_ONCE(ARRAY_SIZE(sdp->srcu_lock_count) != + ARRAY_SIZE(sdp->srcu_unlock_count)); + level = rcu_num_lvls - 1; + snp_first = sp->level[level]; + for_each_possible_cpu(cpu) { + sdp = per_cpu_ptr(sp->sda, cpu); + spin_lock_init(&ACCESS_PRIVATE(sdp, lock)); + rcu_segcblist_init(&sdp->srcu_cblist); + sdp->srcu_cblist_invoking = false; + sdp->srcu_gp_seq_needed = sp->srcu_gp_seq; + sdp->srcu_gp_seq_needed_exp = sp->srcu_gp_seq; + sdp->mynode = &snp_first[cpu / levelspread[level]]; + for (snp = sdp->mynode; snp != NULL; snp = snp->srcu_parent) { + if (snp->grplo < 0) + snp->grplo = cpu; + snp->grphi = cpu; + } + sdp->cpu = cpu; + INIT_DELAYED_WORK(&sdp->work, srcu_invoke_callbacks); + sdp->sp = sp; + sdp->grpmask = 1 << (cpu - sdp->mynode->grplo); + if (is_static) + continue; + + /* Dynamically allocated, better be no srcu_read_locks()! */ + for (i = 0; i < ARRAY_SIZE(sdp->srcu_lock_count); i++) { + sdp->srcu_lock_count[i] = 0; + sdp->srcu_unlock_count[i] = 0; + } + } +} + +/* + * Initialize non-compile-time initialized fields, including the + * associated srcu_node and srcu_data structures. The is_static + * parameter is passed through to init_srcu_struct_nodes(), and + * also tells us that ->sda has already been wired up to srcu_data. + */ +static int init_srcu_struct_fields(struct srcu_struct *sp, bool is_static) +{ + mutex_init(&sp->srcu_cb_mutex); + mutex_init(&sp->srcu_gp_mutex); + sp->srcu_idx = 0; + sp->srcu_gp_seq = 0; + sp->srcu_barrier_seq = 0; + mutex_init(&sp->srcu_barrier_mutex); + atomic_set(&sp->srcu_barrier_cpu_cnt, 0); + INIT_DELAYED_WORK(&sp->work, process_srcu); + if (!is_static) + sp->sda = alloc_percpu(struct srcu_data); + init_srcu_struct_nodes(sp, is_static); + sp->srcu_gp_seq_needed_exp = 0; + sp->srcu_last_gp_end = ktime_get_mono_fast_ns(); + smp_store_release(&sp->srcu_gp_seq_needed, 0); /* Init done. */ + return sp->sda ? 0 : -ENOMEM; +} + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +int __init_srcu_struct(struct srcu_struct *sp, const char *name, + struct lock_class_key *key) +{ + /* Don't re-initialize a lock while it is held. */ + debug_check_no_locks_freed((void *)sp, sizeof(*sp)); + lockdep_init_map(&sp->dep_map, name, key, 0); + spin_lock_init(&ACCESS_PRIVATE(sp, lock)); + return init_srcu_struct_fields(sp, false); +} +EXPORT_SYMBOL_GPL(__init_srcu_struct); + +#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +/** + * init_srcu_struct - initialize a sleep-RCU structure + * @sp: structure to initialize. + * + * Must invoke this on a given srcu_struct before passing that srcu_struct + * to any other function. Each srcu_struct represents a separate domain + * of SRCU protection. + */ +int init_srcu_struct(struct srcu_struct *sp) +{ + spin_lock_init(&ACCESS_PRIVATE(sp, lock)); + return init_srcu_struct_fields(sp, false); +} +EXPORT_SYMBOL_GPL(init_srcu_struct); + +#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +/* + * First-use initialization of statically allocated srcu_struct + * structure. Wiring up the combining tree is more than can be + * done with compile-time initialization, so this check is added + * to each update-side SRCU primitive. Use sp->lock, which -is- + * compile-time initialized, to resolve races involving multiple + * CPUs trying to garner first-use privileges. + */ +static void check_init_srcu_struct(struct srcu_struct *sp) +{ + unsigned long flags; + + WARN_ON_ONCE(rcu_scheduler_active == RCU_SCHEDULER_INIT); + /* The smp_load_acquire() pairs with the smp_store_release(). */ + if (!rcu_seq_state(smp_load_acquire(&sp->srcu_gp_seq_needed))) /*^^^*/ + return; /* Already initialized. */ + spin_lock_irqsave_rcu_node(sp, flags); + if (!rcu_seq_state(sp->srcu_gp_seq_needed)) { + spin_unlock_irqrestore_rcu_node(sp, flags); + return; + } + init_srcu_struct_fields(sp, true); + spin_unlock_irqrestore_rcu_node(sp, flags); +} + +/* + * Returns approximate total of the readers' ->srcu_lock_count[] values + * for the rank of per-CPU counters specified by idx. + */ +static unsigned long srcu_readers_lock_idx(struct srcu_struct *sp, int idx) +{ + int cpu; + unsigned long sum = 0; + + for_each_possible_cpu(cpu) { + struct srcu_data *cpuc = per_cpu_ptr(sp->sda, cpu); + + sum += READ_ONCE(cpuc->srcu_lock_count[idx]); + } + return sum; +} + +/* + * Returns approximate total of the readers' ->srcu_unlock_count[] values + * for the rank of per-CPU counters specified by idx. + */ +static unsigned long srcu_readers_unlock_idx(struct srcu_struct *sp, int idx) +{ + int cpu; + unsigned long sum = 0; + + for_each_possible_cpu(cpu) { + struct srcu_data *cpuc = per_cpu_ptr(sp->sda, cpu); + + sum += READ_ONCE(cpuc->srcu_unlock_count[idx]); + } + return sum; +} + +/* + * Return true if the number of pre-existing readers is determined to + * be zero. + */ +static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx) +{ + unsigned long unlocks; + + unlocks = srcu_readers_unlock_idx(sp, idx); + + /* + * Make sure that a lock is always counted if the corresponding + * unlock is counted. Needs to be a smp_mb() as the read side may + * contain a read from a variable that is written to before the + * synchronize_srcu() in the write side. In this case smp_mb()s + * A and B act like the store buffering pattern. + * + * This smp_mb() also pairs with smp_mb() C to prevent accesses + * after the synchronize_srcu() from being executed before the + * grace period ends. + */ + smp_mb(); /* A */ + + /* + * If the locks are the same as the unlocks, then there must have + * been no readers on this index at some time in between. This does + * not mean that there are no more readers, as one could have read + * the current index but not have incremented the lock counter yet. + * + * So suppose that the updater is preempted here for so long + * that more than ULONG_MAX non-nested readers come and go in + * the meantime. It turns out that this cannot result in overflow + * because if a reader modifies its unlock count after we read it + * above, then that reader's next load of ->srcu_idx is guaranteed + * to get the new value, which will cause it to operate on the + * other bank of counters, where it cannot contribute to the + * overflow of these counters. This means that there is a maximum + * of 2*NR_CPUS increments, which cannot overflow given current + * systems, especially not on 64-bit systems. + * + * OK, how about nesting? This does impose a limit on nesting + * of floor(ULONG_MAX/NR_CPUS/2), which should be sufficient, + * especially on 64-bit systems. + */ + return srcu_readers_lock_idx(sp, idx) == unlocks; +} + +/** + * srcu_readers_active - returns true if there are readers. and false + * otherwise + * @sp: which srcu_struct to count active readers (holding srcu_read_lock). + * + * Note that this is not an atomic primitive, and can therefore suffer + * severe errors when invoked on an active srcu_struct. That said, it + * can be useful as an error check at cleanup time. + */ +static bool srcu_readers_active(struct srcu_struct *sp) +{ + int cpu; + unsigned long sum = 0; + + for_each_possible_cpu(cpu) { + struct srcu_data *cpuc = per_cpu_ptr(sp->sda, cpu); + + sum += READ_ONCE(cpuc->srcu_lock_count[0]); + sum += READ_ONCE(cpuc->srcu_lock_count[1]); + sum -= READ_ONCE(cpuc->srcu_unlock_count[0]); + sum -= READ_ONCE(cpuc->srcu_unlock_count[1]); + } + return sum; +} + +#define SRCU_INTERVAL 1 + +/* + * Return grace-period delay, zero if there are expedited grace + * periods pending, SRCU_INTERVAL otherwise. + */ +static unsigned long srcu_get_delay(struct srcu_struct *sp) +{ + if (ULONG_CMP_LT(READ_ONCE(sp->srcu_gp_seq), + READ_ONCE(sp->srcu_gp_seq_needed_exp))) + return 0; + return SRCU_INTERVAL; +} + +/* Helper for cleanup_srcu_struct() and cleanup_srcu_struct_quiesced(). */ +void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced) +{ + int cpu; + + if (WARN_ON(!srcu_get_delay(sp))) + return; /* Just leak it! */ + if (WARN_ON(srcu_readers_active(sp))) + return; /* Just leak it! */ + if (quiesced) { + if (WARN_ON(delayed_work_pending(&sp->work))) + return; /* Just leak it! */ + } else { + flush_delayed_work(&sp->work); + } + for_each_possible_cpu(cpu) + if (quiesced) { + if (WARN_ON(delayed_work_pending(&per_cpu_ptr(sp->sda, cpu)->work))) + return; /* Just leak it! */ + } else { + flush_delayed_work(&per_cpu_ptr(sp->sda, cpu)->work); + } + if (WARN_ON(rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) != SRCU_STATE_IDLE) || + WARN_ON(srcu_readers_active(sp))) { + pr_info("%s: Active srcu_struct %p state: %d\n", + __func__, sp, rcu_seq_state(READ_ONCE(sp->srcu_gp_seq))); + return; /* Caller forgot to stop doing call_srcu()? */ + } + free_percpu(sp->sda); + sp->sda = NULL; +} +EXPORT_SYMBOL_GPL(_cleanup_srcu_struct); + +/* + * Counts the new reader in the appropriate per-CPU element of the + * srcu_struct. + * Returns an index that must be passed to the matching srcu_read_unlock(). + */ +int __srcu_read_lock(struct srcu_struct *sp) +{ + int idx; + + idx = READ_ONCE(sp->srcu_idx) & 0x1; + this_cpu_inc(sp->sda->srcu_lock_count[idx]); + smp_mb(); /* B */ /* Avoid leaking the critical section. */ + return idx; +} +EXPORT_SYMBOL_GPL(__srcu_read_lock); + +/* + * Removes the count for the old reader from the appropriate per-CPU + * element of the srcu_struct. Note that this may well be a different + * CPU than that which was incremented by the corresponding srcu_read_lock(). + */ +void __srcu_read_unlock(struct srcu_struct *sp, int idx) +{ + smp_mb(); /* C */ /* Avoid leaking the critical section. */ + this_cpu_inc(sp->sda->srcu_unlock_count[idx]); +} +EXPORT_SYMBOL_GPL(__srcu_read_unlock); + +/* + * We use an adaptive strategy for synchronize_srcu() and especially for + * synchronize_srcu_expedited(). We spin for a fixed time period + * (defined below) to allow SRCU readers to exit their read-side critical + * sections. If there are still some readers after a few microseconds, + * we repeatedly block for 1-millisecond time periods. + */ +#define SRCU_RETRY_CHECK_DELAY 5 + +/* + * Start an SRCU grace period. + */ +static void srcu_gp_start(struct srcu_struct *sp) +{ + struct srcu_data *sdp = this_cpu_ptr(sp->sda); + int state; + + lockdep_assert_held(&ACCESS_PRIVATE(sp, lock)); + WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)); + spin_lock_rcu_node(sdp); /* Interrupts already disabled. */ + rcu_segcblist_advance(&sdp->srcu_cblist, + rcu_seq_current(&sp->srcu_gp_seq)); + (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, + rcu_seq_snap(&sp->srcu_gp_seq)); + spin_unlock_rcu_node(sdp); /* Interrupts remain disabled. */ + smp_mb(); /* Order prior store to ->srcu_gp_seq_needed vs. GP start. */ + rcu_seq_start(&sp->srcu_gp_seq); + state = rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)); + WARN_ON_ONCE(state != SRCU_STATE_SCAN1); +} + +/* + * Track online CPUs to guide callback workqueue placement. + */ +DEFINE_PER_CPU(bool, srcu_online); + +void srcu_online_cpu(unsigned int cpu) +{ + WRITE_ONCE(per_cpu(srcu_online, cpu), true); +} + +void srcu_offline_cpu(unsigned int cpu) +{ + WRITE_ONCE(per_cpu(srcu_online, cpu), false); +} + +/* + * Place the workqueue handler on the specified CPU if online, otherwise + * just run it whereever. This is useful for placing workqueue handlers + * that are to invoke the specified CPU's callbacks. + */ +static bool srcu_queue_delayed_work_on(int cpu, struct workqueue_struct *wq, + struct delayed_work *dwork, + unsigned long delay) +{ + bool ret; + + preempt_disable(); + if (READ_ONCE(per_cpu(srcu_online, cpu))) + ret = queue_delayed_work_on(cpu, wq, dwork, delay); + else + ret = queue_delayed_work(wq, dwork, delay); + preempt_enable(); + return ret; +} + +/* + * Schedule callback invocation for the specified srcu_data structure, + * if possible, on the corresponding CPU. + */ +static void srcu_schedule_cbs_sdp(struct srcu_data *sdp, unsigned long delay) +{ + srcu_queue_delayed_work_on(sdp->cpu, rcu_gp_wq, &sdp->work, delay); +} + +/* + * Schedule callback invocation for all srcu_data structures associated + * with the specified srcu_node structure that have callbacks for the + * just-completed grace period, the one corresponding to idx. If possible, + * schedule this invocation on the corresponding CPUs. + */ +static void srcu_schedule_cbs_snp(struct srcu_struct *sp, struct srcu_node *snp, + unsigned long mask, unsigned long delay) +{ + int cpu; + + for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) { + if (!(mask & (1 << (cpu - snp->grplo)))) + continue; + srcu_schedule_cbs_sdp(per_cpu_ptr(sp->sda, cpu), delay); + } +} + +/* + * Note the end of an SRCU grace period. Initiates callback invocation + * and starts a new grace period if needed. + * + * The ->srcu_cb_mutex acquisition does not protect any data, but + * instead prevents more than one grace period from starting while we + * are initiating callback invocation. This allows the ->srcu_have_cbs[] + * array to have a finite number of elements. + */ +static void srcu_gp_end(struct srcu_struct *sp) +{ + unsigned long cbdelay; + bool cbs; + bool last_lvl; + int cpu; + unsigned long flags; + unsigned long gpseq; + int idx; + unsigned long mask; + struct srcu_data *sdp; + struct srcu_node *snp; + + /* Prevent more than one additional grace period. */ + mutex_lock(&sp->srcu_cb_mutex); + + /* End the current grace period. */ + spin_lock_irq_rcu_node(sp); + idx = rcu_seq_state(sp->srcu_gp_seq); + WARN_ON_ONCE(idx != SRCU_STATE_SCAN2); + cbdelay = srcu_get_delay(sp); + sp->srcu_last_gp_end = ktime_get_mono_fast_ns(); + rcu_seq_end(&sp->srcu_gp_seq); + gpseq = rcu_seq_current(&sp->srcu_gp_seq); + if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, gpseq)) + sp->srcu_gp_seq_needed_exp = gpseq; + spin_unlock_irq_rcu_node(sp); + mutex_unlock(&sp->srcu_gp_mutex); + /* A new grace period can start at this point. But only one. */ + + /* Initiate callback invocation as needed. */ + idx = rcu_seq_ctr(gpseq) % ARRAY_SIZE(snp->srcu_have_cbs); + rcu_for_each_node_breadth_first(sp, snp) { + spin_lock_irq_rcu_node(snp); + cbs = false; + last_lvl = snp >= sp->level[rcu_num_lvls - 1]; + if (last_lvl) + cbs = snp->srcu_have_cbs[idx] == gpseq; + snp->srcu_have_cbs[idx] = gpseq; + rcu_seq_set_state(&snp->srcu_have_cbs[idx], 1); + if (ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, gpseq)) + snp->srcu_gp_seq_needed_exp = gpseq; + mask = snp->srcu_data_have_cbs[idx]; + snp->srcu_data_have_cbs[idx] = 0; + spin_unlock_irq_rcu_node(snp); + if (cbs) + srcu_schedule_cbs_snp(sp, snp, mask, cbdelay); + + /* Occasionally prevent srcu_data counter wrap. */ + if (!(gpseq & counter_wrap_check) && last_lvl) + for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) { + sdp = per_cpu_ptr(sp->sda, cpu); + spin_lock_irqsave_rcu_node(sdp, flags); + if (ULONG_CMP_GE(gpseq, + sdp->srcu_gp_seq_needed + 100)) + sdp->srcu_gp_seq_needed = gpseq; + if (ULONG_CMP_GE(gpseq, + sdp->srcu_gp_seq_needed_exp + 100)) + sdp->srcu_gp_seq_needed_exp = gpseq; + spin_unlock_irqrestore_rcu_node(sdp, flags); + } + } + + /* Callback initiation done, allow grace periods after next. */ + mutex_unlock(&sp->srcu_cb_mutex); + + /* Start a new grace period if needed. */ + spin_lock_irq_rcu_node(sp); + gpseq = rcu_seq_current(&sp->srcu_gp_seq); + if (!rcu_seq_state(gpseq) && + ULONG_CMP_LT(gpseq, sp->srcu_gp_seq_needed)) { + srcu_gp_start(sp); + spin_unlock_irq_rcu_node(sp); + srcu_reschedule(sp, 0); + } else { + spin_unlock_irq_rcu_node(sp); + } +} + +/* + * Funnel-locking scheme to scalably mediate many concurrent expedited + * grace-period requests. This function is invoked for the first known + * expedited request for a grace period that has already been requested, + * but without expediting. To start a completely new grace period, + * whether expedited or not, use srcu_funnel_gp_start() instead. + */ +static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp, + unsigned long s) +{ + unsigned long flags; + + for (; snp != NULL; snp = snp->srcu_parent) { + if (rcu_seq_done(&sp->srcu_gp_seq, s) || + ULONG_CMP_GE(READ_ONCE(snp->srcu_gp_seq_needed_exp), s)) + return; + spin_lock_irqsave_rcu_node(snp, flags); + if (ULONG_CMP_GE(snp->srcu_gp_seq_needed_exp, s)) { + spin_unlock_irqrestore_rcu_node(snp, flags); + return; + } + WRITE_ONCE(snp->srcu_gp_seq_needed_exp, s); + spin_unlock_irqrestore_rcu_node(snp, flags); + } + spin_lock_irqsave_rcu_node(sp, flags); + if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s)) + sp->srcu_gp_seq_needed_exp = s; + spin_unlock_irqrestore_rcu_node(sp, flags); +} + +/* + * Funnel-locking scheme to scalably mediate many concurrent grace-period + * requests. The winner has to do the work of actually starting grace + * period s. Losers must either ensure that their desired grace-period + * number is recorded on at least their leaf srcu_node structure, or they + * must take steps to invoke their own callbacks. + * + * Note that this function also does the work of srcu_funnel_exp_start(), + * in some cases by directly invoking it. + */ +static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, + unsigned long s, bool do_norm) +{ + unsigned long flags; + int idx = rcu_seq_ctr(s) % ARRAY_SIZE(sdp->mynode->srcu_have_cbs); + struct srcu_node *snp = sdp->mynode; + unsigned long snp_seq; + + /* Each pass through the loop does one level of the srcu_node tree. */ + for (; snp != NULL; snp = snp->srcu_parent) { + if (rcu_seq_done(&sp->srcu_gp_seq, s) && snp != sdp->mynode) + return; /* GP already done and CBs recorded. */ + spin_lock_irqsave_rcu_node(snp, flags); + if (ULONG_CMP_GE(snp->srcu_have_cbs[idx], s)) { + snp_seq = snp->srcu_have_cbs[idx]; + if (snp == sdp->mynode && snp_seq == s) + snp->srcu_data_have_cbs[idx] |= sdp->grpmask; + spin_unlock_irqrestore_rcu_node(snp, flags); + if (snp == sdp->mynode && snp_seq != s) { + srcu_schedule_cbs_sdp(sdp, do_norm + ? SRCU_INTERVAL + : 0); + return; + } + if (!do_norm) + srcu_funnel_exp_start(sp, snp, s); + return; + } + snp->srcu_have_cbs[idx] = s; + if (snp == sdp->mynode) + snp->srcu_data_have_cbs[idx] |= sdp->grpmask; + if (!do_norm && ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, s)) + snp->srcu_gp_seq_needed_exp = s; + spin_unlock_irqrestore_rcu_node(snp, flags); + } + + /* Top of tree, must ensure the grace period will be started. */ + spin_lock_irqsave_rcu_node(sp, flags); + if (ULONG_CMP_LT(sp->srcu_gp_seq_needed, s)) { + /* + * Record need for grace period s. Pair with load + * acquire setting up for initialization. + */ + smp_store_release(&sp->srcu_gp_seq_needed, s); /*^^^*/ + } + if (!do_norm && ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s)) + sp->srcu_gp_seq_needed_exp = s; + + /* If grace period not already done and none in progress, start it. */ + if (!rcu_seq_done(&sp->srcu_gp_seq, s) && + rcu_seq_state(sp->srcu_gp_seq) == SRCU_STATE_IDLE) { + WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)); + srcu_gp_start(sp); + queue_delayed_work(rcu_gp_wq, &sp->work, srcu_get_delay(sp)); + } + spin_unlock_irqrestore_rcu_node(sp, flags); +} + +/* + * Wait until all readers counted by array index idx complete, but + * loop an additional time if there is an expedited grace period pending. + * The caller must ensure that ->srcu_idx is not changed while checking. + */ +static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount) +{ + for (;;) { + if (srcu_readers_active_idx_check(sp, idx)) + return true; + if (--trycount + !srcu_get_delay(sp) <= 0) + return false; + udelay(SRCU_RETRY_CHECK_DELAY); + } +} + +/* + * Increment the ->srcu_idx counter so that future SRCU readers will + * use the other rank of the ->srcu_(un)lock_count[] arrays. This allows + * us to wait for pre-existing readers in a starvation-free manner. + */ +static void srcu_flip(struct srcu_struct *sp) +{ + /* + * Ensure that if this updater saw a given reader's increment + * from __srcu_read_lock(), that reader was using an old value + * of ->srcu_idx. Also ensure that if a given reader sees the + * new value of ->srcu_idx, this updater's earlier scans cannot + * have seen that reader's increments (which is OK, because this + * grace period need not wait on that reader). + */ + smp_mb(); /* E */ /* Pairs with B and C. */ + + WRITE_ONCE(sp->srcu_idx, sp->srcu_idx + 1); + + /* + * Ensure that if the updater misses an __srcu_read_unlock() + * increment, that task's next __srcu_read_lock() will see the + * above counter update. Note that both this memory barrier + * and the one in srcu_readers_active_idx_check() provide the + * guarantee for __srcu_read_lock(). + */ + smp_mb(); /* D */ /* Pairs with C. */ +} + +/* + * If SRCU is likely idle, return true, otherwise return false. + * + * Note that it is OK for several current from-idle requests for a new + * grace period from idle to specify expediting because they will all end + * up requesting the same grace period anyhow. So no loss. + * + * Note also that if any CPU (including the current one) is still invoking + * callbacks, this function will nevertheless say "idle". This is not + * ideal, but the overhead of checking all CPUs' callback lists is even + * less ideal, especially on large systems. Furthermore, the wakeup + * can happen before the callback is fully removed, so we have no choice + * but to accept this type of error. + * + * This function is also subject to counter-wrap errors, but let's face + * it, if this function was preempted for enough time for the counters + * to wrap, it really doesn't matter whether or not we expedite the grace + * period. The extra overhead of a needlessly expedited grace period is + * negligible when amoritized over that time period, and the extra latency + * of a needlessly non-expedited grace period is similarly negligible. + */ +static bool srcu_might_be_idle(struct srcu_struct *sp) +{ + unsigned long curseq; + unsigned long flags; + struct srcu_data *sdp; + unsigned long t; + + /* If the local srcu_data structure has callbacks, not idle. */ + local_irq_save(flags); + sdp = this_cpu_ptr(sp->sda); + if (rcu_segcblist_pend_cbs(&sdp->srcu_cblist)) { + local_irq_restore(flags); + return false; /* Callbacks already present, so not idle. */ + } + local_irq_restore(flags); + + /* + * No local callbacks, so probabalistically probe global state. + * Exact information would require acquiring locks, which would + * kill scalability, hence the probabalistic nature of the probe. + */ + + /* First, see if enough time has passed since the last GP. */ + t = ktime_get_mono_fast_ns(); + if (exp_holdoff == 0 || + time_in_range_open(t, sp->srcu_last_gp_end, + sp->srcu_last_gp_end + exp_holdoff)) + return false; /* Too soon after last GP. */ + + /* Next, check for probable idleness. */ + curseq = rcu_seq_current(&sp->srcu_gp_seq); + smp_mb(); /* Order ->srcu_gp_seq with ->srcu_gp_seq_needed. */ + if (ULONG_CMP_LT(curseq, READ_ONCE(sp->srcu_gp_seq_needed))) + return false; /* Grace period in progress, so not idle. */ + smp_mb(); /* Order ->srcu_gp_seq with prior access. */ + if (curseq != rcu_seq_current(&sp->srcu_gp_seq)) + return false; /* GP # changed, so not idle. */ + return true; /* With reasonable probability, idle! */ +} + +/* + * SRCU callback function to leak a callback. + */ +static void srcu_leak_callback(struct rcu_head *rhp) +{ +} + +/* + * Enqueue an SRCU callback on the srcu_data structure associated with + * the current CPU and the specified srcu_struct structure, initiating + * grace-period processing if it is not already running. + * + * Note that all CPUs must agree that the grace period extended beyond + * all pre-existing SRCU read-side critical section. On systems with + * more than one CPU, this means that when "func()" is invoked, each CPU + * is guaranteed to have executed a full memory barrier since the end of + * its last corresponding SRCU read-side critical section whose beginning + * preceded the call to call_srcu(). It also means that each CPU executing + * an SRCU read-side critical section that continues beyond the start of + * "func()" must have executed a memory barrier after the call_srcu() + * but before the beginning of that SRCU read-side critical section. + * Note that these guarantees include CPUs that are offline, idle, or + * executing in user mode, as well as CPUs that are executing in the kernel. + * + * Furthermore, if CPU A invoked call_srcu() and CPU B invoked the + * resulting SRCU callback function "func()", then both CPU A and CPU + * B are guaranteed to execute a full memory barrier during the time + * interval between the call to call_srcu() and the invocation of "func()". + * This guarantee applies even if CPU A and CPU B are the same CPU (but + * again only if the system has more than one CPU). + * + * Of course, these guarantees apply only for invocations of call_srcu(), + * srcu_read_lock(), and srcu_read_unlock() that are all passed the same + * srcu_struct structure. + */ +void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, + rcu_callback_t func, bool do_norm) +{ + unsigned long flags; + bool needexp = false; + bool needgp = false; + unsigned long s; + struct srcu_data *sdp; + + check_init_srcu_struct(sp); + if (debug_rcu_head_queue(rhp)) { + /* Probable double call_srcu(), so leak the callback. */ + WRITE_ONCE(rhp->func, srcu_leak_callback); + WARN_ONCE(1, "call_srcu(): Leaked duplicate callback\n"); + return; + } + rhp->func = func; + local_irq_save(flags); + sdp = this_cpu_ptr(sp->sda); + spin_lock_rcu_node(sdp); + rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp, false); + rcu_segcblist_advance(&sdp->srcu_cblist, + rcu_seq_current(&sp->srcu_gp_seq)); + s = rcu_seq_snap(&sp->srcu_gp_seq); + (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, s); + if (ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s)) { + sdp->srcu_gp_seq_needed = s; + needgp = true; + } + if (!do_norm && ULONG_CMP_LT(sdp->srcu_gp_seq_needed_exp, s)) { + sdp->srcu_gp_seq_needed_exp = s; + needexp = true; + } + spin_unlock_irqrestore_rcu_node(sdp, flags); + if (needgp) + srcu_funnel_gp_start(sp, sdp, s, do_norm); + else if (needexp) + srcu_funnel_exp_start(sp, sdp->mynode, s); +} + +/** + * call_srcu() - Queue a callback for invocation after an SRCU grace period + * @sp: srcu_struct in queue the callback + * @rhp: structure to be used for queueing the SRCU callback. + * @func: function to be invoked after the SRCU grace period + * + * The callback function will be invoked some time after a full SRCU + * grace period elapses, in other words after all pre-existing SRCU + * read-side critical sections have completed. However, the callback + * function might well execute concurrently with other SRCU read-side + * critical sections that started after call_srcu() was invoked. SRCU + * read-side critical sections are delimited by srcu_read_lock() and + * srcu_read_unlock(), and may be nested. + * + * The callback will be invoked from process context, but must nevertheless + * be fast and must not block. + */ +void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, + rcu_callback_t func) +{ + __call_srcu(sp, rhp, func, true); +} +EXPORT_SYMBOL_GPL(call_srcu); + +/* + * Helper function for synchronize_srcu() and synchronize_srcu_expedited(). + */ +static void __synchronize_srcu(struct srcu_struct *sp, bool do_norm) +{ + struct rcu_synchronize rcu; + + RCU_LOCKDEP_WARN(lock_is_held(&sp->dep_map) || + lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_srcu() in same-type SRCU (or in RCU) read-side critical section"); + + if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) + return; + might_sleep(); + check_init_srcu_struct(sp); + init_completion(&rcu.completion); + init_rcu_head_on_stack(&rcu.head); + __call_srcu(sp, &rcu.head, wakeme_after_rcu, do_norm); + wait_for_completion(&rcu.completion); + destroy_rcu_head_on_stack(&rcu.head); + + /* + * Make sure that later code is ordered after the SRCU grace + * period. This pairs with the spin_lock_irq_rcu_node() + * in srcu_invoke_callbacks(). Unlike Tree RCU, this is needed + * because the current CPU might have been totally uninvolved with + * (and thus unordered against) that grace period. + */ + smp_mb(); +} + +/** + * synchronize_srcu_expedited - Brute-force SRCU grace period + * @sp: srcu_struct with which to synchronize. + * + * Wait for an SRCU grace period to elapse, but be more aggressive about + * spinning rather than blocking when waiting. + * + * Note that synchronize_srcu_expedited() has the same deadlock and + * memory-ordering properties as does synchronize_srcu(). + */ +void synchronize_srcu_expedited(struct srcu_struct *sp) +{ + __synchronize_srcu(sp, rcu_gp_is_normal()); +} +EXPORT_SYMBOL_GPL(synchronize_srcu_expedited); + +/** + * synchronize_srcu - wait for prior SRCU read-side critical-section completion + * @sp: srcu_struct with which to synchronize. + * + * Wait for the count to drain to zero of both indexes. To avoid the + * possible starvation of synchronize_srcu(), it waits for the count of + * the index=((->srcu_idx & 1) ^ 1) to drain to zero at first, + * and then flip the srcu_idx and wait for the count of the other index. + * + * Can block; must be called from process context. + * + * Note that it is illegal to call synchronize_srcu() from the corresponding + * SRCU read-side critical section; doing so will result in deadlock. + * However, it is perfectly legal to call synchronize_srcu() on one + * srcu_struct from some other srcu_struct's read-side critical section, + * as long as the resulting graph of srcu_structs is acyclic. + * + * There are memory-ordering constraints implied by synchronize_srcu(). + * On systems with more than one CPU, when synchronize_srcu() returns, + * each CPU is guaranteed to have executed a full memory barrier since + * the end of its last corresponding SRCU-sched read-side critical section + * whose beginning preceded the call to synchronize_srcu(). In addition, + * each CPU having an SRCU read-side critical section that extends beyond + * the return from synchronize_srcu() is guaranteed to have executed a + * full memory barrier after the beginning of synchronize_srcu() and before + * the beginning of that SRCU read-side critical section. Note that these + * guarantees include CPUs that are offline, idle, or executing in user mode, + * as well as CPUs that are executing in the kernel. + * + * Furthermore, if CPU A invoked synchronize_srcu(), which returned + * to its caller on CPU B, then both CPU A and CPU B are guaranteed + * to have executed a full memory barrier during the execution of + * synchronize_srcu(). This guarantee applies even if CPU A and CPU B + * are the same CPU, but again only if the system has more than one CPU. + * + * Of course, these memory-ordering guarantees apply only when + * synchronize_srcu(), srcu_read_lock(), and srcu_read_unlock() are + * passed the same srcu_struct structure. + * + * If SRCU is likely idle, expedite the first request. This semantic + * was provided by Classic SRCU, and is relied upon by its users, so TREE + * SRCU must also provide it. Note that detecting idleness is heuristic + * and subject to both false positives and negatives. + */ +void synchronize_srcu(struct srcu_struct *sp) +{ + if (srcu_might_be_idle(sp) || rcu_gp_is_expedited()) + synchronize_srcu_expedited(sp); + else + __synchronize_srcu(sp, true); +} +EXPORT_SYMBOL_GPL(synchronize_srcu); + +/* + * Callback function for srcu_barrier() use. + */ +static void srcu_barrier_cb(struct rcu_head *rhp) +{ + struct srcu_data *sdp; + struct srcu_struct *sp; + + sdp = container_of(rhp, struct srcu_data, srcu_barrier_head); + sp = sdp->sp; + if (atomic_dec_and_test(&sp->srcu_barrier_cpu_cnt)) + complete(&sp->srcu_barrier_completion); +} + +/** + * srcu_barrier - Wait until all in-flight call_srcu() callbacks complete. + * @sp: srcu_struct on which to wait for in-flight callbacks. + */ +void srcu_barrier(struct srcu_struct *sp) +{ + int cpu; + struct srcu_data *sdp; + unsigned long s = rcu_seq_snap(&sp->srcu_barrier_seq); + + check_init_srcu_struct(sp); + mutex_lock(&sp->srcu_barrier_mutex); + if (rcu_seq_done(&sp->srcu_barrier_seq, s)) { + smp_mb(); /* Force ordering following return. */ + mutex_unlock(&sp->srcu_barrier_mutex); + return; /* Someone else did our work for us. */ + } + rcu_seq_start(&sp->srcu_barrier_seq); + init_completion(&sp->srcu_barrier_completion); + + /* Initial count prevents reaching zero until all CBs are posted. */ + atomic_set(&sp->srcu_barrier_cpu_cnt, 1); + + /* + * Each pass through this loop enqueues a callback, but only + * on CPUs already having callbacks enqueued. Note that if + * a CPU already has callbacks enqueue, it must have already + * registered the need for a future grace period, so all we + * need do is enqueue a callback that will use the same + * grace period as the last callback already in the queue. + */ + for_each_possible_cpu(cpu) { + sdp = per_cpu_ptr(sp->sda, cpu); + spin_lock_irq_rcu_node(sdp); + atomic_inc(&sp->srcu_barrier_cpu_cnt); + sdp->srcu_barrier_head.func = srcu_barrier_cb; + debug_rcu_head_queue(&sdp->srcu_barrier_head); + if (!rcu_segcblist_entrain(&sdp->srcu_cblist, + &sdp->srcu_barrier_head, 0)) { + debug_rcu_head_unqueue(&sdp->srcu_barrier_head); + atomic_dec(&sp->srcu_barrier_cpu_cnt); + } + spin_unlock_irq_rcu_node(sdp); + } + + /* Remove the initial count, at which point reaching zero can happen. */ + if (atomic_dec_and_test(&sp->srcu_barrier_cpu_cnt)) + complete(&sp->srcu_barrier_completion); + wait_for_completion(&sp->srcu_barrier_completion); + + rcu_seq_end(&sp->srcu_barrier_seq); + mutex_unlock(&sp->srcu_barrier_mutex); +} +EXPORT_SYMBOL_GPL(srcu_barrier); + +/** + * srcu_batches_completed - return batches completed. + * @sp: srcu_struct on which to report batch completion. + * + * Report the number of batches, correlated with, but not necessarily + * precisely the same as, the number of grace periods that have elapsed. + */ +unsigned long srcu_batches_completed(struct srcu_struct *sp) +{ + return sp->srcu_idx; +} +EXPORT_SYMBOL_GPL(srcu_batches_completed); + +/* + * Core SRCU state machine. Push state bits of ->srcu_gp_seq + * to SRCU_STATE_SCAN2, and invoke srcu_gp_end() when scan has + * completed in that state. + */ +static void srcu_advance_state(struct srcu_struct *sp) +{ + int idx; + + mutex_lock(&sp->srcu_gp_mutex); + + /* + * Because readers might be delayed for an extended period after + * fetching ->srcu_idx for their index, at any point in time there + * might well be readers using both idx=0 and idx=1. We therefore + * need to wait for readers to clear from both index values before + * invoking a callback. + * + * The load-acquire ensures that we see the accesses performed + * by the prior grace period. + */ + idx = rcu_seq_state(smp_load_acquire(&sp->srcu_gp_seq)); /* ^^^ */ + if (idx == SRCU_STATE_IDLE) { + spin_lock_irq_rcu_node(sp); + if (ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)) { + WARN_ON_ONCE(rcu_seq_state(sp->srcu_gp_seq)); + spin_unlock_irq_rcu_node(sp); + mutex_unlock(&sp->srcu_gp_mutex); + return; + } + idx = rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)); + if (idx == SRCU_STATE_IDLE) + srcu_gp_start(sp); + spin_unlock_irq_rcu_node(sp); + if (idx != SRCU_STATE_IDLE) { + mutex_unlock(&sp->srcu_gp_mutex); + return; /* Someone else started the grace period. */ + } + } + + if (rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) == SRCU_STATE_SCAN1) { + idx = 1 ^ (sp->srcu_idx & 1); + if (!try_check_zero(sp, idx, 1)) { + mutex_unlock(&sp->srcu_gp_mutex); + return; /* readers present, retry later. */ + } + srcu_flip(sp); + rcu_seq_set_state(&sp->srcu_gp_seq, SRCU_STATE_SCAN2); + } + + if (rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) == SRCU_STATE_SCAN2) { + + /* + * SRCU read-side critical sections are normally short, + * so check at least twice in quick succession after a flip. + */ + idx = 1 ^ (sp->srcu_idx & 1); + if (!try_check_zero(sp, idx, 2)) { + mutex_unlock(&sp->srcu_gp_mutex); + return; /* readers present, retry later. */ + } + srcu_gp_end(sp); /* Releases ->srcu_gp_mutex. */ + } +} + +/* + * Invoke a limited number of SRCU callbacks that have passed through + * their grace period. If there are more to do, SRCU will reschedule + * the workqueue. Note that needed memory barriers have been executed + * in this task's context by srcu_readers_active_idx_check(). + */ +static void srcu_invoke_callbacks(struct work_struct *work) +{ + bool more; + struct rcu_cblist ready_cbs; + struct rcu_head *rhp; + struct srcu_data *sdp; + struct srcu_struct *sp; + + sdp = container_of(work, struct srcu_data, work.work); + sp = sdp->sp; + rcu_cblist_init(&ready_cbs); + spin_lock_irq_rcu_node(sdp); + rcu_segcblist_advance(&sdp->srcu_cblist, + rcu_seq_current(&sp->srcu_gp_seq)); + if (sdp->srcu_cblist_invoking || + !rcu_segcblist_ready_cbs(&sdp->srcu_cblist)) { + spin_unlock_irq_rcu_node(sdp); + return; /* Someone else on the job or nothing to do. */ + } + + /* We are on the job! Extract and invoke ready callbacks. */ + sdp->srcu_cblist_invoking = true; + rcu_segcblist_extract_done_cbs(&sdp->srcu_cblist, &ready_cbs); + spin_unlock_irq_rcu_node(sdp); + rhp = rcu_cblist_dequeue(&ready_cbs); + for (; rhp != NULL; rhp = rcu_cblist_dequeue(&ready_cbs)) { + debug_rcu_head_unqueue(rhp); + local_bh_disable(); + rhp->func(rhp); + local_bh_enable(); + } + + /* + * Update counts, accelerate new callbacks, and if needed, + * schedule another round of callback invocation. + */ + spin_lock_irq_rcu_node(sdp); + rcu_segcblist_insert_count(&sdp->srcu_cblist, &ready_cbs); + (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, + rcu_seq_snap(&sp->srcu_gp_seq)); + sdp->srcu_cblist_invoking = false; + more = rcu_segcblist_ready_cbs(&sdp->srcu_cblist); + spin_unlock_irq_rcu_node(sdp); + if (more) + srcu_schedule_cbs_sdp(sdp, 0); +} + +/* + * Finished one round of SRCU grace period. Start another if there are + * more SRCU callbacks queued, otherwise put SRCU into not-running state. + */ +static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay) +{ + bool pushgp = true; + + spin_lock_irq_rcu_node(sp); + if (ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)) { + if (!WARN_ON_ONCE(rcu_seq_state(sp->srcu_gp_seq))) { + /* All requests fulfilled, time to go idle. */ + pushgp = false; + } + } else if (!rcu_seq_state(sp->srcu_gp_seq)) { + /* Outstanding request and no GP. Start one. */ + srcu_gp_start(sp); + } + spin_unlock_irq_rcu_node(sp); + + if (pushgp) + queue_delayed_work(rcu_gp_wq, &sp->work, delay); +} + +/* + * This is the work-queue function that handles SRCU grace periods. + */ +static void process_srcu(struct work_struct *work) +{ + struct srcu_struct *sp; + + sp = container_of(work, struct srcu_struct, work.work); + + srcu_advance_state(sp); + srcu_reschedule(sp, srcu_get_delay(sp)); +} + +void srcutorture_get_gp_data(enum rcutorture_type test_type, + struct srcu_struct *sp, int *flags, + unsigned long *gp_seq) +{ + if (test_type != SRCU_FLAVOR) + return; + *flags = 0; + *gp_seq = rcu_seq_current(&sp->srcu_gp_seq); +} +EXPORT_SYMBOL_GPL(srcutorture_get_gp_data); + +void srcu_torture_stats_print(struct srcu_struct *sp, char *tt, char *tf) +{ + int cpu; + int idx; + unsigned long s0 = 0, s1 = 0; + + idx = sp->srcu_idx & 0x1; + pr_alert("%s%s Tree SRCU g%ld per-CPU(idx=%d):", + tt, tf, rcu_seq_current(&sp->srcu_gp_seq), idx); + for_each_possible_cpu(cpu) { + unsigned long l0, l1; + unsigned long u0, u1; + long c0, c1; + struct srcu_data *sdp; + + sdp = per_cpu_ptr(sp->sda, cpu); + u0 = sdp->srcu_unlock_count[!idx]; + u1 = sdp->srcu_unlock_count[idx]; + + /* + * Make sure that a lock is always counted if the corresponding + * unlock is counted. + */ + smp_rmb(); + + l0 = sdp->srcu_lock_count[!idx]; + l1 = sdp->srcu_lock_count[idx]; + + c0 = l0 - u0; + c1 = l1 - u1; + pr_cont(" %d(%ld,%ld %1p)", + cpu, c0, c1, rcu_segcblist_head(&sdp->srcu_cblist)); + s0 += c0; + s1 += c1; + } + pr_cont(" T(%ld,%ld)\n", s0, s1); +} +EXPORT_SYMBOL_GPL(srcu_torture_stats_print); + +static int __init srcu_bootup_announce(void) +{ + pr_info("Hierarchical SRCU implementation.\n"); + if (exp_holdoff != DEFAULT_SRCU_EXP_HOLDOFF) + pr_info("\tNon-default auto-expedite holdoff of %lu ns.\n", exp_holdoff); + return 0; +} +early_initcall(srcu_bootup_announce); diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c new file mode 100644 index 000000000..3f943efcf --- /dev/null +++ b/kernel/rcu/sync.c @@ -0,0 +1,240 @@ +/* + * RCU-based infrastructure for lightweight reader-writer locking + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright (c) 2015, Red Hat, Inc. + * + * Author: Oleg Nesterov <oleg@redhat.com> + */ + +#include <linux/rcu_sync.h> +#include <linux/sched.h> + +#ifdef CONFIG_PROVE_RCU +#define __INIT_HELD(func) .held = func, +#else +#define __INIT_HELD(func) +#endif + +static const struct { + void (*sync)(void); + void (*call)(struct rcu_head *, void (*)(struct rcu_head *)); + void (*wait)(void); +#ifdef CONFIG_PROVE_RCU + int (*held)(void); +#endif +} gp_ops[] = { + [RCU_SYNC] = { + .sync = synchronize_rcu, + .call = call_rcu, + .wait = rcu_barrier, + __INIT_HELD(rcu_read_lock_held) + }, + [RCU_SCHED_SYNC] = { + .sync = synchronize_sched, + .call = call_rcu_sched, + .wait = rcu_barrier_sched, + __INIT_HELD(rcu_read_lock_sched_held) + }, + [RCU_BH_SYNC] = { + .sync = synchronize_rcu_bh, + .call = call_rcu_bh, + .wait = rcu_barrier_bh, + __INIT_HELD(rcu_read_lock_bh_held) + }, +}; + +enum { GP_IDLE = 0, GP_PENDING, GP_PASSED }; +enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY }; + +#define rss_lock gp_wait.lock + +#ifdef CONFIG_PROVE_RCU +void rcu_sync_lockdep_assert(struct rcu_sync *rsp) +{ + RCU_LOCKDEP_WARN(!gp_ops[rsp->gp_type].held(), + "suspicious rcu_sync_is_idle() usage"); +} + +EXPORT_SYMBOL_GPL(rcu_sync_lockdep_assert); +#endif + +/** + * rcu_sync_init() - Initialize an rcu_sync structure + * @rsp: Pointer to rcu_sync structure to be initialized + * @type: Flavor of RCU with which to synchronize rcu_sync structure + */ +void rcu_sync_init(struct rcu_sync *rsp, enum rcu_sync_type type) +{ + memset(rsp, 0, sizeof(*rsp)); + init_waitqueue_head(&rsp->gp_wait); + rsp->gp_type = type; +} + +/** + * rcu_sync_enter_start - Force readers onto slow path for multiple updates + * @rsp: Pointer to rcu_sync structure to use for synchronization + * + * Must be called after rcu_sync_init() and before first use. + * + * Ensures rcu_sync_is_idle() returns false and rcu_sync_{enter,exit}() + * pairs turn into NO-OPs. + */ +void rcu_sync_enter_start(struct rcu_sync *rsp) +{ + rsp->gp_count++; + rsp->gp_state = GP_PASSED; +} + +/** + * rcu_sync_enter() - Force readers onto slowpath + * @rsp: Pointer to rcu_sync structure to use for synchronization + * + * This function is used by updaters who need readers to make use of + * a slowpath during the update. After this function returns, all + * subsequent calls to rcu_sync_is_idle() will return false, which + * tells readers to stay off their fastpaths. A later call to + * rcu_sync_exit() re-enables reader slowpaths. + * + * When called in isolation, rcu_sync_enter() must wait for a grace + * period, however, closely spaced calls to rcu_sync_enter() can + * optimize away the grace-period wait via a state machine implemented + * by rcu_sync_enter(), rcu_sync_exit(), and rcu_sync_func(). + */ +void rcu_sync_enter(struct rcu_sync *rsp) +{ + bool need_wait, need_sync; + + spin_lock_irq(&rsp->rss_lock); + need_wait = rsp->gp_count++; + need_sync = rsp->gp_state == GP_IDLE; + if (need_sync) + rsp->gp_state = GP_PENDING; + spin_unlock_irq(&rsp->rss_lock); + + BUG_ON(need_wait && need_sync); + + if (need_sync) { + gp_ops[rsp->gp_type].sync(); + rsp->gp_state = GP_PASSED; + wake_up_all(&rsp->gp_wait); + } else if (need_wait) { + wait_event(rsp->gp_wait, rsp->gp_state == GP_PASSED); + } else { + /* + * Possible when there's a pending CB from a rcu_sync_exit(). + * Nobody has yet been allowed the 'fast' path and thus we can + * avoid doing any sync(). The callback will get 'dropped'. + */ + BUG_ON(rsp->gp_state != GP_PASSED); + } +} + +/** + * rcu_sync_func() - Callback function managing reader access to fastpath + * @rhp: Pointer to rcu_head in rcu_sync structure to use for synchronization + * + * This function is passed to one of the call_rcu() functions by + * rcu_sync_exit(), so that it is invoked after a grace period following the + * that invocation of rcu_sync_exit(). It takes action based on events that + * have taken place in the meantime, so that closely spaced rcu_sync_enter() + * and rcu_sync_exit() pairs need not wait for a grace period. + * + * If another rcu_sync_enter() is invoked before the grace period + * ended, reset state to allow the next rcu_sync_exit() to let the + * readers back onto their fastpaths (after a grace period). If both + * another rcu_sync_enter() and its matching rcu_sync_exit() are invoked + * before the grace period ended, re-invoke call_rcu() on behalf of that + * rcu_sync_exit(). Otherwise, set all state back to idle so that readers + * can again use their fastpaths. + */ +static void rcu_sync_func(struct rcu_head *rhp) +{ + struct rcu_sync *rsp = container_of(rhp, struct rcu_sync, cb_head); + unsigned long flags; + + BUG_ON(rsp->gp_state != GP_PASSED); + BUG_ON(rsp->cb_state == CB_IDLE); + + spin_lock_irqsave(&rsp->rss_lock, flags); + if (rsp->gp_count) { + /* + * A new rcu_sync_begin() has happened; drop the callback. + */ + rsp->cb_state = CB_IDLE; + } else if (rsp->cb_state == CB_REPLAY) { + /* + * A new rcu_sync_exit() has happened; requeue the callback + * to catch a later GP. + */ + rsp->cb_state = CB_PENDING; + gp_ops[rsp->gp_type].call(&rsp->cb_head, rcu_sync_func); + } else { + /* + * We're at least a GP after rcu_sync_exit(); eveybody will now + * have observed the write side critical section. Let 'em rip!. + */ + rsp->cb_state = CB_IDLE; + rsp->gp_state = GP_IDLE; + } + spin_unlock_irqrestore(&rsp->rss_lock, flags); +} + +/** + * rcu_sync_exit() - Allow readers back onto fast patch after grace period + * @rsp: Pointer to rcu_sync structure to use for synchronization + * + * This function is used by updaters who have completed, and can therefore + * now allow readers to make use of their fastpaths after a grace period + * has elapsed. After this grace period has completed, all subsequent + * calls to rcu_sync_is_idle() will return true, which tells readers that + * they can once again use their fastpaths. + */ +void rcu_sync_exit(struct rcu_sync *rsp) +{ + spin_lock_irq(&rsp->rss_lock); + if (!--rsp->gp_count) { + if (rsp->cb_state == CB_IDLE) { + rsp->cb_state = CB_PENDING; + gp_ops[rsp->gp_type].call(&rsp->cb_head, rcu_sync_func); + } else if (rsp->cb_state == CB_PENDING) { + rsp->cb_state = CB_REPLAY; + } + } + spin_unlock_irq(&rsp->rss_lock); +} + +/** + * rcu_sync_dtor() - Clean up an rcu_sync structure + * @rsp: Pointer to rcu_sync structure to be cleaned up + */ +void rcu_sync_dtor(struct rcu_sync *rsp) +{ + int cb_state; + + BUG_ON(rsp->gp_count); + + spin_lock_irq(&rsp->rss_lock); + if (rsp->cb_state == CB_REPLAY) + rsp->cb_state = CB_PENDING; + cb_state = rsp->cb_state; + spin_unlock_irq(&rsp->rss_lock); + + if (cb_state != CB_IDLE) { + gp_ops[rsp->gp_type].wait(); + BUG_ON(rsp->cb_state != CB_IDLE); + } +} diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c new file mode 100644 index 000000000..befc9321a --- /dev/null +++ b/kernel/rcu/tiny.c @@ -0,0 +1,239 @@ +/* + * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2008 + * + * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * + * For detailed explanation of Read-Copy Update mechanism see - + * Documentation/RCU + */ +#include <linux/completion.h> +#include <linux/interrupt.h> +#include <linux/notifier.h> +#include <linux/rcupdate_wait.h> +#include <linux/kernel.h> +#include <linux/export.h> +#include <linux/mutex.h> +#include <linux/sched.h> +#include <linux/types.h> +#include <linux/init.h> +#include <linux/time.h> +#include <linux/cpu.h> +#include <linux/prefetch.h> + +#include "rcu.h" + +/* Global control variables for rcupdate callback mechanism. */ +struct rcu_ctrlblk { + struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */ + struct rcu_head **donetail; /* ->next pointer of last "done" CB. */ + struct rcu_head **curtail; /* ->next pointer of last CB. */ +}; + +/* Definition for rcupdate control block. */ +static struct rcu_ctrlblk rcu_sched_ctrlblk = { + .donetail = &rcu_sched_ctrlblk.rcucblist, + .curtail = &rcu_sched_ctrlblk.rcucblist, +}; + +static struct rcu_ctrlblk rcu_bh_ctrlblk = { + .donetail = &rcu_bh_ctrlblk.rcucblist, + .curtail = &rcu_bh_ctrlblk.rcucblist, +}; + +void rcu_barrier_bh(void) +{ + wait_rcu_gp(call_rcu_bh); +} +EXPORT_SYMBOL(rcu_barrier_bh); + +void rcu_barrier_sched(void) +{ + wait_rcu_gp(call_rcu_sched); +} +EXPORT_SYMBOL(rcu_barrier_sched); + +/* + * Helper function for rcu_sched_qs() and rcu_bh_qs(). + * Also irqs are disabled to avoid confusion due to interrupt handlers + * invoking call_rcu(). + */ +static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) +{ + if (rcp->donetail != rcp->curtail) { + rcp->donetail = rcp->curtail; + return 1; + } + + return 0; +} + +/* + * Record an rcu quiescent state. And an rcu_bh quiescent state while we + * are at it, given that any rcu quiescent state is also an rcu_bh + * quiescent state. Use "+" instead of "||" to defeat short circuiting. + */ +void rcu_sched_qs(void) +{ + unsigned long flags; + + local_irq_save(flags); + if (rcu_qsctr_help(&rcu_sched_ctrlblk) + + rcu_qsctr_help(&rcu_bh_ctrlblk)) + raise_softirq(RCU_SOFTIRQ); + local_irq_restore(flags); +} + +/* + * Record an rcu_bh quiescent state. + */ +void rcu_bh_qs(void) +{ + unsigned long flags; + + local_irq_save(flags); + if (rcu_qsctr_help(&rcu_bh_ctrlblk)) + raise_softirq(RCU_SOFTIRQ); + local_irq_restore(flags); +} + +/* + * Check to see if the scheduling-clock interrupt came from an extended + * quiescent state, and, if so, tell RCU about it. This function must + * be called from hardirq context. It is normally called from the + * scheduling-clock interrupt. + */ +void rcu_check_callbacks(int user) +{ + if (user) + rcu_sched_qs(); + if (user || !in_softirq()) + rcu_bh_qs(); +} + +/* + * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure + * whose grace period has elapsed. + */ +static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) +{ + struct rcu_head *next, *list; + unsigned long flags; + + /* Move the ready-to-invoke callbacks to a local list. */ + local_irq_save(flags); + if (rcp->donetail == &rcp->rcucblist) { + /* No callbacks ready, so just leave. */ + local_irq_restore(flags); + return; + } + list = rcp->rcucblist; + rcp->rcucblist = *rcp->donetail; + *rcp->donetail = NULL; + if (rcp->curtail == rcp->donetail) + rcp->curtail = &rcp->rcucblist; + rcp->donetail = &rcp->rcucblist; + local_irq_restore(flags); + + /* Invoke the callbacks on the local list. */ + while (list) { + next = list->next; + prefetch(next); + debug_rcu_head_unqueue(list); + local_bh_disable(); + __rcu_reclaim("", list); + local_bh_enable(); + list = next; + } +} + +static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused) +{ + __rcu_process_callbacks(&rcu_sched_ctrlblk); + __rcu_process_callbacks(&rcu_bh_ctrlblk); +} + +/* + * Wait for a grace period to elapse. But it is illegal to invoke + * synchronize_sched() from within an RCU read-side critical section. + * Therefore, any legal call to synchronize_sched() is a quiescent + * state, and so on a UP system, synchronize_sched() need do nothing. + * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the + * benefits of doing might_sleep() to reduce latency.) + * + * Cool, huh? (Due to Josh Triplett.) + */ +void synchronize_sched(void) +{ + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_sched() in RCU read-side critical section"); +} +EXPORT_SYMBOL_GPL(synchronize_sched); + +/* + * Helper function for call_rcu() and call_rcu_bh(). + */ +static void __call_rcu(struct rcu_head *head, + rcu_callback_t func, + struct rcu_ctrlblk *rcp) +{ + unsigned long flags; + + debug_rcu_head_queue(head); + head->func = func; + head->next = NULL; + + local_irq_save(flags); + *rcp->curtail = head; + rcp->curtail = &head->next; + local_irq_restore(flags); + + if (unlikely(is_idle_task(current))) { + /* force scheduling for rcu_sched_qs() */ + resched_cpu(0); + } +} + +/* + * Post an RCU callback to be invoked after the end of an RCU-sched grace + * period. But since we have but one CPU, that would be after any + * quiescent state. + */ +void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) +{ + __call_rcu(head, func, &rcu_sched_ctrlblk); +} +EXPORT_SYMBOL_GPL(call_rcu_sched); + +/* + * Post an RCU bottom-half callback to be invoked after any subsequent + * quiescent state. + */ +void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) +{ + __call_rcu(head, func, &rcu_bh_ctrlblk); +} +EXPORT_SYMBOL_GPL(call_rcu_bh); + +void __init rcu_init(void) +{ + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); + rcu_early_boot_tests(); +} diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c new file mode 100644 index 000000000..f7e89c989 --- /dev/null +++ b/kernel/rcu/tree.c @@ -0,0 +1,4187 @@ +/* + * Read-Copy Update mechanism for mutual exclusion + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2008 + * + * Authors: Dipankar Sarma <dipankar@in.ibm.com> + * Manfred Spraul <manfred@colorfullife.com> + * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version + * + * Based on the original work by Paul McKenney <paulmck@us.ibm.com> + * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. + * + * For detailed explanation of Read-Copy Update mechanism see - + * Documentation/RCU + */ + +#define pr_fmt(fmt) "rcu: " fmt + +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/spinlock.h> +#include <linux/smp.h> +#include <linux/rcupdate_wait.h> +#include <linux/interrupt.h> +#include <linux/sched.h> +#include <linux/sched/debug.h> +#include <linux/nmi.h> +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/export.h> +#include <linux/completion.h> +#include <linux/moduleparam.h> +#include <linux/percpu.h> +#include <linux/notifier.h> +#include <linux/cpu.h> +#include <linux/mutex.h> +#include <linux/time.h> +#include <linux/kernel_stat.h> +#include <linux/wait.h> +#include <linux/kthread.h> +#include <uapi/linux/sched/types.h> +#include <linux/prefetch.h> +#include <linux/delay.h> +#include <linux/stop_machine.h> +#include <linux/random.h> +#include <linux/trace_events.h> +#include <linux/suspend.h> +#include <linux/ftrace.h> + +#include "tree.h" +#include "rcu.h" + +#ifdef MODULE_PARAM_PREFIX +#undef MODULE_PARAM_PREFIX +#endif +#define MODULE_PARAM_PREFIX "rcutree." + +/* Data structures. */ + +/* + * In order to export the rcu_state name to the tracing tools, it + * needs to be added in the __tracepoint_string section. + * This requires defining a separate variable tp_<sname>_varname + * that points to the string being used, and this will allow + * the tracing userspace tools to be able to decipher the string + * address to the matching string. + */ +#ifdef CONFIG_TRACING +# define DEFINE_RCU_TPS(sname) \ +static char sname##_varname[] = #sname; \ +static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname; +# define RCU_STATE_NAME(sname) sname##_varname +#else +# define DEFINE_RCU_TPS(sname) +# define RCU_STATE_NAME(sname) __stringify(sname) +#endif + +#define RCU_STATE_INITIALIZER(sname, sabbr, cr) \ +DEFINE_RCU_TPS(sname) \ +static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data); \ +struct rcu_state sname##_state = { \ + .level = { &sname##_state.node[0] }, \ + .rda = &sname##_data, \ + .call = cr, \ + .gp_state = RCU_GP_IDLE, \ + .gp_seq = (0UL - 300UL) << RCU_SEQ_CTR_SHIFT, \ + .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ + .name = RCU_STATE_NAME(sname), \ + .abbr = sabbr, \ + .exp_mutex = __MUTEX_INITIALIZER(sname##_state.exp_mutex), \ + .exp_wake_mutex = __MUTEX_INITIALIZER(sname##_state.exp_wake_mutex), \ + .ofl_lock = __SPIN_LOCK_UNLOCKED(sname##_state.ofl_lock), \ +} + +RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched); +RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); + +static struct rcu_state *const rcu_state_p; +LIST_HEAD(rcu_struct_flavors); + +/* Dump rcu_node combining tree at boot to verify correct setup. */ +static bool dump_tree; +module_param(dump_tree, bool, 0444); +/* Control rcu_node-tree auto-balancing at boot time. */ +static bool rcu_fanout_exact; +module_param(rcu_fanout_exact, bool, 0444); +/* Increase (but not decrease) the RCU_FANOUT_LEAF at boot time. */ +static int rcu_fanout_leaf = RCU_FANOUT_LEAF; +module_param(rcu_fanout_leaf, int, 0444); +int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; +/* Number of rcu_nodes at specified level. */ +int num_rcu_lvl[] = NUM_RCU_LVL_INIT; +int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ +/* panic() on RCU Stall sysctl. */ +int sysctl_panic_on_rcu_stall __read_mostly; + +/* + * The rcu_scheduler_active variable is initialized to the value + * RCU_SCHEDULER_INACTIVE and transitions RCU_SCHEDULER_INIT just before the + * first task is spawned. So when this variable is RCU_SCHEDULER_INACTIVE, + * RCU can assume that there is but one task, allowing RCU to (for example) + * optimize synchronize_rcu() to a simple barrier(). When this variable + * is RCU_SCHEDULER_INIT, RCU must actually do all the hard work required + * to detect real grace periods. This variable is also used to suppress + * boot-time false positives from lockdep-RCU error checking. Finally, it + * transitions from RCU_SCHEDULER_INIT to RCU_SCHEDULER_RUNNING after RCU + * is fully initialized, including all of its kthreads having been spawned. + */ +int rcu_scheduler_active __read_mostly; +EXPORT_SYMBOL_GPL(rcu_scheduler_active); + +/* + * The rcu_scheduler_fully_active variable transitions from zero to one + * during the early_initcall() processing, which is after the scheduler + * is capable of creating new tasks. So RCU processing (for example, + * creating tasks for RCU priority boosting) must be delayed until after + * rcu_scheduler_fully_active transitions from zero to one. We also + * currently delay invocation of any RCU callbacks until after this point. + * + * It might later prove better for people registering RCU callbacks during + * early boot to take responsibility for these callbacks, but one step at + * a time. + */ +static int rcu_scheduler_fully_active __read_mostly; + +static void +rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, + struct rcu_node *rnp, unsigned long gps, unsigned long flags); +static void rcu_init_new_rnp(struct rcu_node *rnp_leaf); +static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf); +static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); +static void invoke_rcu_core(void); +static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); +static void rcu_report_exp_rdp(struct rcu_state *rsp, + struct rcu_data *rdp, bool wake); +static void sync_sched_exp_online_cleanup(int cpu); + +/* rcuc/rcub kthread realtime priority */ +static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0; +module_param(kthread_prio, int, 0644); + +/* Delay in jiffies for grace-period initialization delays, debug only. */ + +static int gp_preinit_delay; +module_param(gp_preinit_delay, int, 0444); +static int gp_init_delay; +module_param(gp_init_delay, int, 0444); +static int gp_cleanup_delay; +module_param(gp_cleanup_delay, int, 0444); + +/* Retreive RCU kthreads priority for rcutorture */ +int rcu_get_gp_kthreads_prio(void) +{ + return kthread_prio; +} +EXPORT_SYMBOL_GPL(rcu_get_gp_kthreads_prio); + +/* + * Number of grace periods between delays, normalized by the duration of + * the delay. The longer the delay, the more the grace periods between + * each delay. The reason for this normalization is that it means that, + * for non-zero delays, the overall slowdown of grace periods is constant + * regardless of the duration of the delay. This arrangement balances + * the need for long delays to increase some race probabilities with the + * need for fast grace periods to increase other race probabilities. + */ +#define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays. */ + +/* + * Compute the mask of online CPUs for the specified rcu_node structure. + * This will not be stable unless the rcu_node structure's ->lock is + * held, but the bit corresponding to the current CPU will be stable + * in most contexts. + */ +unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp) +{ + return READ_ONCE(rnp->qsmaskinitnext); +} + +/* + * Return true if an RCU grace period is in progress. The READ_ONCE()s + * permit this function to be invoked without holding the root rcu_node + * structure's ->lock, but of course results can be subject to change. + */ +static int rcu_gp_in_progress(struct rcu_state *rsp) +{ + return rcu_seq_state(rcu_seq_current(&rsp->gp_seq)); +} + +/* + * Note a quiescent state. Because we do not need to know + * how many quiescent states passed, just if there was at least + * one since the start of the grace period, this just sets a flag. + * The caller must have disabled preemption. + */ +void rcu_sched_qs(void) +{ + RCU_LOCKDEP_WARN(preemptible(), "rcu_sched_qs() invoked with preemption enabled!!!"); + if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.s)) + return; + trace_rcu_grace_period(TPS("rcu_sched"), + __this_cpu_read(rcu_sched_data.gp_seq), + TPS("cpuqs")); + __this_cpu_write(rcu_sched_data.cpu_no_qs.b.norm, false); + if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp)) + return; + __this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, false); + rcu_report_exp_rdp(&rcu_sched_state, + this_cpu_ptr(&rcu_sched_data), true); +} + +void rcu_bh_qs(void) +{ + RCU_LOCKDEP_WARN(preemptible(), "rcu_bh_qs() invoked with preemption enabled!!!"); + if (__this_cpu_read(rcu_bh_data.cpu_no_qs.s)) { + trace_rcu_grace_period(TPS("rcu_bh"), + __this_cpu_read(rcu_bh_data.gp_seq), + TPS("cpuqs")); + __this_cpu_write(rcu_bh_data.cpu_no_qs.b.norm, false); + } +} + +/* + * Steal a bit from the bottom of ->dynticks for idle entry/exit + * control. Initially this is for TLB flushing. + */ +#define RCU_DYNTICK_CTRL_MASK 0x1 +#define RCU_DYNTICK_CTRL_CTR (RCU_DYNTICK_CTRL_MASK + 1) +#ifndef rcu_eqs_special_exit +#define rcu_eqs_special_exit() do { } while (0) +#endif + +static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { + .dynticks_nesting = 1, + .dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE, + .dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR), +}; + +/* + * Record entry into an extended quiescent state. This is only to be + * called when not already in an extended quiescent state. + */ +static void rcu_dynticks_eqs_enter(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + int seq; + + /* + * CPUs seeing atomic_add_return() must see prior RCU read-side + * critical sections, and we also must force ordering with the + * next idle sojourn. + */ + seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks); + /* Better be in an extended quiescent state! */ + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && + (seq & RCU_DYNTICK_CTRL_CTR)); + /* Better not have special action (TLB flush) pending! */ + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && + (seq & RCU_DYNTICK_CTRL_MASK)); +} + +/* + * Record exit from an extended quiescent state. This is only to be + * called from an extended quiescent state. + */ +static void rcu_dynticks_eqs_exit(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + int seq; + + /* + * CPUs seeing atomic_add_return() must see prior idle sojourns, + * and we also must force ordering with the next RCU read-side + * critical section. + */ + seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks); + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && + !(seq & RCU_DYNTICK_CTRL_CTR)); + if (seq & RCU_DYNTICK_CTRL_MASK) { + atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdtp->dynticks); + smp_mb__after_atomic(); /* _exit after clearing mask. */ + /* Prefer duplicate flushes to losing a flush. */ + rcu_eqs_special_exit(); + } +} + +/* + * Reset the current CPU's ->dynticks counter to indicate that the + * newly onlined CPU is no longer in an extended quiescent state. + * This will either leave the counter unchanged, or increment it + * to the next non-quiescent value. + * + * The non-atomic test/increment sequence works because the upper bits + * of the ->dynticks counter are manipulated only by the corresponding CPU, + * or when the corresponding CPU is offline. + */ +static void rcu_dynticks_eqs_online(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + if (atomic_read(&rdtp->dynticks) & RCU_DYNTICK_CTRL_CTR) + return; + atomic_add(RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks); +} + +/* + * Is the current CPU in an extended quiescent state? + * + * No ordering, as we are sampling CPU-local information. + */ +bool rcu_dynticks_curr_cpu_in_eqs(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + return !(atomic_read(&rdtp->dynticks) & RCU_DYNTICK_CTRL_CTR); +} + +/* + * Snapshot the ->dynticks counter with full ordering so as to allow + * stable comparison of this counter with past and future snapshots. + */ +int rcu_dynticks_snap(struct rcu_dynticks *rdtp) +{ + int snap = atomic_add_return(0, &rdtp->dynticks); + + return snap & ~RCU_DYNTICK_CTRL_MASK; +} + +/* + * Return true if the snapshot returned from rcu_dynticks_snap() + * indicates that RCU is in an extended quiescent state. + */ +static bool rcu_dynticks_in_eqs(int snap) +{ + return !(snap & RCU_DYNTICK_CTRL_CTR); +} + +/* + * Return true if the CPU corresponding to the specified rcu_dynticks + * structure has spent some time in an extended quiescent state since + * rcu_dynticks_snap() returned the specified snapshot. + */ +static bool rcu_dynticks_in_eqs_since(struct rcu_dynticks *rdtp, int snap) +{ + return snap != rcu_dynticks_snap(rdtp); +} + +/* + * Set the special (bottom) bit of the specified CPU so that it + * will take special action (such as flushing its TLB) on the + * next exit from an extended quiescent state. Returns true if + * the bit was successfully set, or false if the CPU was not in + * an extended quiescent state. + */ +bool rcu_eqs_special_set(int cpu) +{ + int old; + int new; + struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); + + do { + old = atomic_read(&rdtp->dynticks); + if (old & RCU_DYNTICK_CTRL_CTR) + return false; + new = old | RCU_DYNTICK_CTRL_MASK; + } while (atomic_cmpxchg(&rdtp->dynticks, old, new) != old); + return true; +} + +/* + * Let the RCU core know that this CPU has gone through the scheduler, + * which is a quiescent state. This is called when the need for a + * quiescent state is urgent, so we burn an atomic operation and full + * memory barriers to let the RCU core know about it, regardless of what + * this CPU might (or might not) do in the near future. + * + * We inform the RCU core by emulating a zero-duration dyntick-idle period. + * + * The caller must have disabled interrupts and must not be idle. + */ +static void rcu_momentary_dyntick_idle(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + int special; + + raw_cpu_write(rcu_dynticks.rcu_need_heavy_qs, false); + special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks); + /* It is illegal to call this from idle state. */ + WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR)); +} + +/* + * Note a context switch. This is a quiescent state for RCU-sched, + * and requires special handling for preemptible RCU. + * The caller must have disabled interrupts. + */ +void rcu_note_context_switch(bool preempt) +{ + barrier(); /* Avoid RCU read-side critical sections leaking down. */ + trace_rcu_utilization(TPS("Start context switch")); + rcu_sched_qs(); + rcu_preempt_note_context_switch(preempt); + /* Load rcu_urgent_qs before other flags. */ + if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) + goto out; + this_cpu_write(rcu_dynticks.rcu_urgent_qs, false); + if (unlikely(raw_cpu_read(rcu_dynticks.rcu_need_heavy_qs))) + rcu_momentary_dyntick_idle(); + this_cpu_inc(rcu_dynticks.rcu_qs_ctr); + if (!preempt) + rcu_tasks_qs(current); +out: + trace_rcu_utilization(TPS("End context switch")); + barrier(); /* Avoid RCU read-side critical sections leaking up. */ +} +EXPORT_SYMBOL_GPL(rcu_note_context_switch); + +/* + * Register a quiescent state for all RCU flavors. If there is an + * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight + * dyntick-idle quiescent state visible to other CPUs (but only for those + * RCU flavors in desperate need of a quiescent state, which will normally + * be none of them). Either way, do a lightweight quiescent state for + * all RCU flavors. + * + * The barrier() calls are redundant in the common case when this is + * called externally, but just in case this is called from within this + * file. + * + */ +void rcu_all_qs(void) +{ + unsigned long flags; + + if (!raw_cpu_read(rcu_dynticks.rcu_urgent_qs)) + return; + preempt_disable(); + /* Load rcu_urgent_qs before other flags. */ + if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) { + preempt_enable(); + return; + } + this_cpu_write(rcu_dynticks.rcu_urgent_qs, false); + barrier(); /* Avoid RCU read-side critical sections leaking down. */ + if (unlikely(raw_cpu_read(rcu_dynticks.rcu_need_heavy_qs))) { + local_irq_save(flags); + rcu_momentary_dyntick_idle(); + local_irq_restore(flags); + } + if (unlikely(raw_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))) + rcu_sched_qs(); + this_cpu_inc(rcu_dynticks.rcu_qs_ctr); + barrier(); /* Avoid RCU read-side critical sections leaking up. */ + preempt_enable(); +} +EXPORT_SYMBOL_GPL(rcu_all_qs); + +#define DEFAULT_RCU_BLIMIT 10 /* Maximum callbacks per rcu_do_batch. */ +static long blimit = DEFAULT_RCU_BLIMIT; +#define DEFAULT_RCU_QHIMARK 10000 /* If this many pending, ignore blimit. */ +static long qhimark = DEFAULT_RCU_QHIMARK; +#define DEFAULT_RCU_QLOMARK 100 /* Once only this many pending, use blimit. */ +static long qlowmark = DEFAULT_RCU_QLOMARK; + +module_param(blimit, long, 0444); +module_param(qhimark, long, 0444); +module_param(qlowmark, long, 0444); + +static ulong jiffies_till_first_fqs = ULONG_MAX; +static ulong jiffies_till_next_fqs = ULONG_MAX; +static bool rcu_kick_kthreads; + +static int param_set_first_fqs_jiffies(const char *val, const struct kernel_param *kp) +{ + ulong j; + int ret = kstrtoul(val, 0, &j); + + if (!ret) + WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : j); + return ret; +} + +static int param_set_next_fqs_jiffies(const char *val, const struct kernel_param *kp) +{ + ulong j; + int ret = kstrtoul(val, 0, &j); + + if (!ret) + WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : (j ?: 1)); + return ret; +} + +static struct kernel_param_ops first_fqs_jiffies_ops = { + .set = param_set_first_fqs_jiffies, + .get = param_get_ulong, +}; + +static struct kernel_param_ops next_fqs_jiffies_ops = { + .set = param_set_next_fqs_jiffies, + .get = param_get_ulong, +}; + +module_param_cb(jiffies_till_first_fqs, &first_fqs_jiffies_ops, &jiffies_till_first_fqs, 0644); +module_param_cb(jiffies_till_next_fqs, &next_fqs_jiffies_ops, &jiffies_till_next_fqs, 0644); +module_param(rcu_kick_kthreads, bool, 0644); + +/* + * How long the grace period must be before we start recruiting + * quiescent-state help from rcu_note_context_switch(). + */ +static ulong jiffies_till_sched_qs = HZ / 10; +module_param(jiffies_till_sched_qs, ulong, 0444); + +static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp)); +static void force_quiescent_state(struct rcu_state *rsp); +static int rcu_pending(void); + +/* + * Return the number of RCU GPs completed thus far for debug & stats. + */ +unsigned long rcu_get_gp_seq(void) +{ + return READ_ONCE(rcu_state_p->gp_seq); +} +EXPORT_SYMBOL_GPL(rcu_get_gp_seq); + +/* + * Return the number of RCU-sched GPs completed thus far for debug & stats. + */ +unsigned long rcu_sched_get_gp_seq(void) +{ + return READ_ONCE(rcu_sched_state.gp_seq); +} +EXPORT_SYMBOL_GPL(rcu_sched_get_gp_seq); + +/* + * Return the number of RCU-bh GPs completed thus far for debug & stats. + */ +unsigned long rcu_bh_get_gp_seq(void) +{ + return READ_ONCE(rcu_bh_state.gp_seq); +} +EXPORT_SYMBOL_GPL(rcu_bh_get_gp_seq); + +/* + * Return the number of RCU expedited batches completed thus far for + * debug & stats. Odd numbers mean that a batch is in progress, even + * numbers mean idle. The value returned will thus be roughly double + * the cumulative batches since boot. + */ +unsigned long rcu_exp_batches_completed(void) +{ + return rcu_state_p->expedited_sequence; +} +EXPORT_SYMBOL_GPL(rcu_exp_batches_completed); + +/* + * Return the number of RCU-sched expedited batches completed thus far + * for debug & stats. Similar to rcu_exp_batches_completed(). + */ +unsigned long rcu_exp_batches_completed_sched(void) +{ + return rcu_sched_state.expedited_sequence; +} +EXPORT_SYMBOL_GPL(rcu_exp_batches_completed_sched); + +/* + * Force a quiescent state. + */ +void rcu_force_quiescent_state(void) +{ + force_quiescent_state(rcu_state_p); +} +EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); + +/* + * Force a quiescent state for RCU BH. + */ +void rcu_bh_force_quiescent_state(void) +{ + force_quiescent_state(&rcu_bh_state); +} +EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); + +/* + * Force a quiescent state for RCU-sched. + */ +void rcu_sched_force_quiescent_state(void) +{ + force_quiescent_state(&rcu_sched_state); +} +EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); + +/* + * Show the state of the grace-period kthreads. + */ +void show_rcu_gp_kthreads(void) +{ + int cpu; + struct rcu_data *rdp; + struct rcu_node *rnp; + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) { + pr_info("%s: wait state: %d ->state: %#lx\n", + rsp->name, rsp->gp_state, rsp->gp_kthread->state); + rcu_for_each_node_breadth_first(rsp, rnp) { + if (ULONG_CMP_GE(rsp->gp_seq, rnp->gp_seq_needed)) + continue; + pr_info("\trcu_node %d:%d ->gp_seq %lu ->gp_seq_needed %lu\n", + rnp->grplo, rnp->grphi, rnp->gp_seq, + rnp->gp_seq_needed); + if (!rcu_is_leaf_node(rnp)) + continue; + for_each_leaf_node_possible_cpu(rnp, cpu) { + rdp = per_cpu_ptr(rsp->rda, cpu); + if (rdp->gpwrap || + ULONG_CMP_GE(rsp->gp_seq, + rdp->gp_seq_needed)) + continue; + pr_info("\tcpu %d ->gp_seq_needed %lu\n", + cpu, rdp->gp_seq_needed); + } + } + /* sched_show_task(rsp->gp_kthread); */ + } +} +EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads); + +/* + * Send along grace-period-related data for rcutorture diagnostics. + */ +void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, + unsigned long *gp_seq) +{ + struct rcu_state *rsp = NULL; + + switch (test_type) { + case RCU_FLAVOR: + rsp = rcu_state_p; + break; + case RCU_BH_FLAVOR: + rsp = &rcu_bh_state; + break; + case RCU_SCHED_FLAVOR: + rsp = &rcu_sched_state; + break; + default: + break; + } + if (rsp == NULL) + return; + *flags = READ_ONCE(rsp->gp_flags); + *gp_seq = rcu_seq_current(&rsp->gp_seq); +} +EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); + +/* + * Return the root node of the specified rcu_state structure. + */ +static struct rcu_node *rcu_get_root(struct rcu_state *rsp) +{ + return &rsp->node[0]; +} + +/* + * Enter an RCU extended quiescent state, which can be either the + * idle loop or adaptive-tickless usermode execution. + * + * We crowbar the ->dynticks_nmi_nesting field to zero to allow for + * the possibility of usermode upcalls having messed up our count + * of interrupt nesting level during the prior busy period. + */ +static void rcu_eqs_enter(bool user) +{ + struct rcu_state *rsp; + struct rcu_data *rdp; + struct rcu_dynticks *rdtp; + + rdtp = this_cpu_ptr(&rcu_dynticks); + WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && + rdtp->dynticks_nesting == 0); + if (rdtp->dynticks_nesting != 1) { + rdtp->dynticks_nesting--; + return; + } + + lockdep_assert_irqs_disabled(); + trace_rcu_dyntick(TPS("Start"), rdtp->dynticks_nesting, 0, rdtp->dynticks); + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); + for_each_rcu_flavor(rsp) { + rdp = this_cpu_ptr(rsp->rda); + do_nocb_deferred_wakeup(rdp); + } + rcu_prepare_for_idle(); + WRITE_ONCE(rdtp->dynticks_nesting, 0); /* Avoid irq-access tearing. */ + rcu_dynticks_eqs_enter(); + rcu_dynticks_task_enter(); +} + +/** + * rcu_idle_enter - inform RCU that current CPU is entering idle + * + * Enter idle mode, in other words, -leave- the mode in which RCU + * read-side critical sections can occur. (Though RCU read-side + * critical sections can occur in irq handlers in idle, a possibility + * handled by irq_enter() and irq_exit().) + * + * If you add or remove a call to rcu_idle_enter(), be sure to test with + * CONFIG_RCU_EQS_DEBUG=y. + */ +void rcu_idle_enter(void) +{ + lockdep_assert_irqs_disabled(); + rcu_eqs_enter(false); +} + +#ifdef CONFIG_NO_HZ_FULL +/** + * rcu_user_enter - inform RCU that we are resuming userspace. + * + * Enter RCU idle mode right before resuming userspace. No use of RCU + * is permitted between this call and rcu_user_exit(). This way the + * CPU doesn't need to maintain the tick for RCU maintenance purposes + * when the CPU runs in userspace. + * + * If you add or remove a call to rcu_user_enter(), be sure to test with + * CONFIG_RCU_EQS_DEBUG=y. + */ +void rcu_user_enter(void) +{ + lockdep_assert_irqs_disabled(); + rcu_eqs_enter(true); +} +#endif /* CONFIG_NO_HZ_FULL */ + +/** + * rcu_nmi_exit - inform RCU of exit from NMI context + * + * If we are returning from the outermost NMI handler that interrupted an + * RCU-idle period, update rdtp->dynticks and rdtp->dynticks_nmi_nesting + * to let the RCU grace-period handling know that the CPU is back to + * being RCU-idle. + * + * If you add or remove a call to rcu_nmi_exit(), be sure to test + * with CONFIG_RCU_EQS_DEBUG=y. + */ +void rcu_nmi_exit(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + /* + * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks. + * (We are exiting an NMI handler, so RCU better be paying attention + * to us!) + */ + WARN_ON_ONCE(rdtp->dynticks_nmi_nesting <= 0); + WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs()); + + /* + * If the nesting level is not 1, the CPU wasn't RCU-idle, so + * leave it in non-RCU-idle state. + */ + if (rdtp->dynticks_nmi_nesting != 1) { + trace_rcu_dyntick(TPS("--="), rdtp->dynticks_nmi_nesting, rdtp->dynticks_nmi_nesting - 2, rdtp->dynticks); + WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* No store tearing. */ + rdtp->dynticks_nmi_nesting - 2); + return; + } + + /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ + trace_rcu_dyntick(TPS("Startirq"), rdtp->dynticks_nmi_nesting, 0, rdtp->dynticks); + WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ + rcu_dynticks_eqs_enter(); +} + +/** + * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle + * + * Exit from an interrupt handler, which might possibly result in entering + * idle mode, in other words, leaving the mode in which read-side critical + * sections can occur. The caller must have disabled interrupts. + * + * This code assumes that the idle loop never does anything that might + * result in unbalanced calls to irq_enter() and irq_exit(). If your + * architecture's idle loop violates this assumption, RCU will give you what + * you deserve, good and hard. But very infrequently and irreproducibly. + * + * Use things like work queues to work around this limitation. + * + * You have been warned. + * + * If you add or remove a call to rcu_irq_exit(), be sure to test with + * CONFIG_RCU_EQS_DEBUG=y. + */ +void rcu_irq_exit(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + lockdep_assert_irqs_disabled(); + if (rdtp->dynticks_nmi_nesting == 1) + rcu_prepare_for_idle(); + rcu_nmi_exit(); + if (rdtp->dynticks_nmi_nesting == 0) + rcu_dynticks_task_enter(); +} + +/* + * Wrapper for rcu_irq_exit() where interrupts are enabled. + * + * If you add or remove a call to rcu_irq_exit_irqson(), be sure to test + * with CONFIG_RCU_EQS_DEBUG=y. + */ +void rcu_irq_exit_irqson(void) +{ + unsigned long flags; + + local_irq_save(flags); + rcu_irq_exit(); + local_irq_restore(flags); +} + +/* + * Exit an RCU extended quiescent state, which can be either the + * idle loop or adaptive-tickless usermode execution. + * + * We crowbar the ->dynticks_nmi_nesting field to DYNTICK_IRQ_NONIDLE to + * allow for the possibility of usermode upcalls messing up our count of + * interrupt nesting level during the busy period that is just now starting. + */ +static void rcu_eqs_exit(bool user) +{ + struct rcu_dynticks *rdtp; + long oldval; + + lockdep_assert_irqs_disabled(); + rdtp = this_cpu_ptr(&rcu_dynticks); + oldval = rdtp->dynticks_nesting; + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0); + if (oldval) { + rdtp->dynticks_nesting++; + return; + } + rcu_dynticks_task_exit(); + rcu_dynticks_eqs_exit(); + rcu_cleanup_after_idle(); + trace_rcu_dyntick(TPS("End"), rdtp->dynticks_nesting, 1, rdtp->dynticks); + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); + WRITE_ONCE(rdtp->dynticks_nesting, 1); + WRITE_ONCE(rdtp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE); +} + +/** + * rcu_idle_exit - inform RCU that current CPU is leaving idle + * + * Exit idle mode, in other words, -enter- the mode in which RCU + * read-side critical sections can occur. + * + * If you add or remove a call to rcu_idle_exit(), be sure to test with + * CONFIG_RCU_EQS_DEBUG=y. + */ +void rcu_idle_exit(void) +{ + unsigned long flags; + + local_irq_save(flags); + rcu_eqs_exit(false); + local_irq_restore(flags); +} + +#ifdef CONFIG_NO_HZ_FULL +/** + * rcu_user_exit - inform RCU that we are exiting userspace. + * + * Exit RCU idle mode while entering the kernel because it can + * run a RCU read side critical section anytime. + * + * If you add or remove a call to rcu_user_exit(), be sure to test with + * CONFIG_RCU_EQS_DEBUG=y. + */ +void rcu_user_exit(void) +{ + rcu_eqs_exit(1); +} +#endif /* CONFIG_NO_HZ_FULL */ + +/** + * rcu_nmi_enter - inform RCU of entry to NMI context + * + * If the CPU was idle from RCU's viewpoint, update rdtp->dynticks and + * rdtp->dynticks_nmi_nesting to let the RCU grace-period handling know + * that the CPU is active. This implementation permits nested NMIs, as + * long as the nesting level does not overflow an int. (You will probably + * run out of stack space first.) + * + * If you add or remove a call to rcu_nmi_enter(), be sure to test + * with CONFIG_RCU_EQS_DEBUG=y. + */ +void rcu_nmi_enter(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + long incby = 2; + + /* Complain about underflow. */ + WARN_ON_ONCE(rdtp->dynticks_nmi_nesting < 0); + + /* + * If idle from RCU viewpoint, atomically increment ->dynticks + * to mark non-idle and increment ->dynticks_nmi_nesting by one. + * Otherwise, increment ->dynticks_nmi_nesting by two. This means + * if ->dynticks_nmi_nesting is equal to one, we are guaranteed + * to be in the outermost NMI handler that interrupted an RCU-idle + * period (observation due to Andy Lutomirski). + */ + if (rcu_dynticks_curr_cpu_in_eqs()) { + rcu_dynticks_eqs_exit(); + incby = 1; + } + trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="), + rdtp->dynticks_nmi_nesting, + rdtp->dynticks_nmi_nesting + incby, rdtp->dynticks); + WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* Prevent store tearing. */ + rdtp->dynticks_nmi_nesting + incby); + barrier(); +} + +/** + * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle + * + * Enter an interrupt handler, which might possibly result in exiting + * idle mode, in other words, entering the mode in which read-side critical + * sections can occur. The caller must have disabled interrupts. + * + * Note that the Linux kernel is fully capable of entering an interrupt + * handler that it never exits, for example when doing upcalls to user mode! + * This code assumes that the idle loop never does upcalls to user mode. + * If your architecture's idle loop does do upcalls to user mode (or does + * anything else that results in unbalanced calls to the irq_enter() and + * irq_exit() functions), RCU will give you what you deserve, good and hard. + * But very infrequently and irreproducibly. + * + * Use things like work queues to work around this limitation. + * + * You have been warned. + * + * If you add or remove a call to rcu_irq_enter(), be sure to test with + * CONFIG_RCU_EQS_DEBUG=y. + */ +void rcu_irq_enter(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + lockdep_assert_irqs_disabled(); + if (rdtp->dynticks_nmi_nesting == 0) + rcu_dynticks_task_exit(); + rcu_nmi_enter(); + if (rdtp->dynticks_nmi_nesting == 1) + rcu_cleanup_after_idle(); +} + +/* + * Wrapper for rcu_irq_enter() where interrupts are enabled. + * + * If you add or remove a call to rcu_irq_enter_irqson(), be sure to test + * with CONFIG_RCU_EQS_DEBUG=y. + */ +void rcu_irq_enter_irqson(void) +{ + unsigned long flags; + + local_irq_save(flags); + rcu_irq_enter(); + local_irq_restore(flags); +} + +/** + * rcu_is_watching - see if RCU thinks that the current CPU is idle + * + * Return true if RCU is watching the running CPU, which means that this + * CPU can safely enter RCU read-side critical sections. In other words, + * if the current CPU is in its idle loop and is neither in an interrupt + * or NMI handler, return true. + */ +bool notrace rcu_is_watching(void) +{ + bool ret; + + preempt_disable_notrace(); + ret = !rcu_dynticks_curr_cpu_in_eqs(); + preempt_enable_notrace(); + return ret; +} +EXPORT_SYMBOL_GPL(rcu_is_watching); + +/* + * If a holdout task is actually running, request an urgent quiescent + * state from its CPU. This is unsynchronized, so migrations can cause + * the request to go to the wrong CPU. Which is OK, all that will happen + * is that the CPU's next context switch will be a bit slower and next + * time around this task will generate another request. + */ +void rcu_request_urgent_qs_task(struct task_struct *t) +{ + int cpu; + + barrier(); + cpu = task_cpu(t); + if (!task_curr(t)) + return; /* This task is not running on that CPU. */ + smp_store_release(per_cpu_ptr(&rcu_dynticks.rcu_urgent_qs, cpu), true); +} + +#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) + +/* + * Is the current CPU online as far as RCU is concerned? + * + * Disable preemption to avoid false positives that could otherwise + * happen due to the current CPU number being sampled, this task being + * preempted, its old CPU being taken offline, resuming on some other CPU, + * then determining that its old CPU is now offline. Because there are + * multiple flavors of RCU, and because this function can be called in the + * midst of updating the flavors while a given CPU coming online or going + * offline, it is necessary to check all flavors. If any of the flavors + * believe that given CPU is online, it is considered to be online. + * + * Disable checking if in an NMI handler because we cannot safely + * report errors from NMI handlers anyway. In addition, it is OK to use + * RCU on an offline processor during initial boot, hence the check for + * rcu_scheduler_fully_active. + */ +bool rcu_lockdep_current_cpu_online(void) +{ + struct rcu_data *rdp; + struct rcu_node *rnp; + struct rcu_state *rsp; + + if (in_nmi() || !rcu_scheduler_fully_active) + return true; + preempt_disable(); + for_each_rcu_flavor(rsp) { + rdp = this_cpu_ptr(rsp->rda); + rnp = rdp->mynode; + if (rdp->grpmask & rcu_rnp_online_cpus(rnp)) { + preempt_enable(); + return true; + } + } + preempt_enable(); + return false; +} +EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); + +#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ + +/** + * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle + * + * If the current CPU is idle or running at a first-level (not nested) + * interrupt from idle, return true. The caller must have at least + * disabled preemption. + */ +static int rcu_is_cpu_rrupt_from_idle(void) +{ + return __this_cpu_read(rcu_dynticks.dynticks_nesting) <= 0 && + __this_cpu_read(rcu_dynticks.dynticks_nmi_nesting) <= 1; +} + +/* + * We are reporting a quiescent state on behalf of some other CPU, so + * it is our responsibility to check for and handle potential overflow + * of the rcu_node ->gp_seq counter with respect to the rcu_data counters. + * After all, the CPU might be in deep idle state, and thus executing no + * code whatsoever. + */ +static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp) +{ + raw_lockdep_assert_held_rcu_node(rnp); + if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + ULONG_MAX / 4, + rnp->gp_seq)) + WRITE_ONCE(rdp->gpwrap, true); + if (ULONG_CMP_LT(rdp->rcu_iw_gp_seq + ULONG_MAX / 4, rnp->gp_seq)) + rdp->rcu_iw_gp_seq = rnp->gp_seq + ULONG_MAX / 4; +} + +/* + * Snapshot the specified CPU's dynticks counter so that we can later + * credit them with an implicit quiescent state. Return 1 if this CPU + * is in dynticks idle mode, which is an extended quiescent state. + */ +static int dyntick_save_progress_counter(struct rcu_data *rdp) +{ + rdp->dynticks_snap = rcu_dynticks_snap(rdp->dynticks); + if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) { + trace_rcu_fqs(rdp->rsp->name, rdp->gp_seq, rdp->cpu, TPS("dti")); + rcu_gpnum_ovf(rdp->mynode, rdp); + return 1; + } + return 0; +} + +/* + * Handler for the irq_work request posted when a grace period has + * gone on for too long, but not yet long enough for an RCU CPU + * stall warning. Set state appropriately, but just complain if + * there is unexpected state on entry. + */ +static void rcu_iw_handler(struct irq_work *iwp) +{ + struct rcu_data *rdp; + struct rcu_node *rnp; + + rdp = container_of(iwp, struct rcu_data, rcu_iw); + rnp = rdp->mynode; + raw_spin_lock_rcu_node(rnp); + if (!WARN_ON_ONCE(!rdp->rcu_iw_pending)) { + rdp->rcu_iw_gp_seq = rnp->gp_seq; + rdp->rcu_iw_pending = false; + } + raw_spin_unlock_rcu_node(rnp); +} + +/* + * Return true if the specified CPU has passed through a quiescent + * state by virtue of being in or having passed through an dynticks + * idle state since the last call to dyntick_save_progress_counter() + * for this same CPU, or by virtue of having been offline. + */ +static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) +{ + unsigned long jtsq; + bool *rnhqp; + bool *ruqp; + struct rcu_node *rnp = rdp->mynode; + + /* + * If the CPU passed through or entered a dynticks idle phase with + * no active irq/NMI handlers, then we can safely pretend that the CPU + * already acknowledged the request to pass through a quiescent + * state. Either way, that CPU cannot possibly be in an RCU + * read-side critical section that started before the beginning + * of the current RCU grace period. + */ + if (rcu_dynticks_in_eqs_since(rdp->dynticks, rdp->dynticks_snap)) { + trace_rcu_fqs(rdp->rsp->name, rdp->gp_seq, rdp->cpu, TPS("dti")); + rdp->dynticks_fqs++; + rcu_gpnum_ovf(rnp, rdp); + return 1; + } + + /* + * Has this CPU encountered a cond_resched() since the beginning + * of the grace period? For this to be the case, the CPU has to + * have noticed the current grace period. This might not be the + * case for nohz_full CPUs looping in the kernel. + */ + jtsq = jiffies_till_sched_qs; + ruqp = per_cpu_ptr(&rcu_dynticks.rcu_urgent_qs, rdp->cpu); + if (time_after(jiffies, rdp->rsp->gp_start + jtsq) && + READ_ONCE(rdp->rcu_qs_ctr_snap) != per_cpu(rcu_dynticks.rcu_qs_ctr, rdp->cpu) && + rcu_seq_current(&rdp->gp_seq) == rnp->gp_seq && !rdp->gpwrap) { + trace_rcu_fqs(rdp->rsp->name, rdp->gp_seq, rdp->cpu, TPS("rqc")); + rcu_gpnum_ovf(rnp, rdp); + return 1; + } else if (time_after(jiffies, rdp->rsp->gp_start + jtsq)) { + /* Load rcu_qs_ctr before store to rcu_urgent_qs. */ + smp_store_release(ruqp, true); + } + + /* If waiting too long on an offline CPU, complain. */ + if (!(rdp->grpmask & rcu_rnp_online_cpus(rnp)) && + time_after(jiffies, rdp->rsp->gp_start + HZ)) { + bool onl; + struct rcu_node *rnp1; + + WARN_ON(1); /* Offline CPUs are supposed to report QS! */ + pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n", + __func__, rnp->grplo, rnp->grphi, rnp->level, + (long)rnp->gp_seq, (long)rnp->completedqs); + for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent) + pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx ->rcu_gp_init_mask %#lx\n", + __func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask); + onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp)); + pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n", + __func__, rdp->cpu, ".o"[onl], + (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags, + (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags); + return 1; /* Break things loose after complaining. */ + } + + /* + * A CPU running for an extended time within the kernel can + * delay RCU grace periods. When the CPU is in NO_HZ_FULL mode, + * even context-switching back and forth between a pair of + * in-kernel CPU-bound tasks cannot advance grace periods. + * So if the grace period is old enough, make the CPU pay attention. + * Note that the unsynchronized assignments to the per-CPU + * rcu_need_heavy_qs variable are safe. Yes, setting of + * bits can be lost, but they will be set again on the next + * force-quiescent-state pass. So lost bit sets do not result + * in incorrect behavior, merely in a grace period lasting + * a few jiffies longer than it might otherwise. Because + * there are at most four threads involved, and because the + * updates are only once every few jiffies, the probability of + * lossage (and thus of slight grace-period extension) is + * quite low. + */ + rnhqp = &per_cpu(rcu_dynticks.rcu_need_heavy_qs, rdp->cpu); + if (!READ_ONCE(*rnhqp) && + (time_after(jiffies, rdp->rsp->gp_start + jtsq) || + time_after(jiffies, rdp->rsp->jiffies_resched))) { + WRITE_ONCE(*rnhqp, true); + /* Store rcu_need_heavy_qs before rcu_urgent_qs. */ + smp_store_release(ruqp, true); + rdp->rsp->jiffies_resched += jtsq; /* Re-enable beating. */ + } + + /* + * If more than halfway to RCU CPU stall-warning time, do a + * resched_cpu() to try to loosen things up a bit. Also check to + * see if the CPU is getting hammered with interrupts, but only + * once per grace period, just to keep the IPIs down to a dull roar. + */ + if (jiffies - rdp->rsp->gp_start > rcu_jiffies_till_stall_check() / 2) { + resched_cpu(rdp->cpu); + if (IS_ENABLED(CONFIG_IRQ_WORK) && + !rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq && + (rnp->ffmask & rdp->grpmask)) { + init_irq_work(&rdp->rcu_iw, rcu_iw_handler); + rdp->rcu_iw_pending = true; + rdp->rcu_iw_gp_seq = rnp->gp_seq; + irq_work_queue_on(&rdp->rcu_iw, rdp->cpu); + } + } + + return 0; +} + +static void record_gp_stall_check_time(struct rcu_state *rsp) +{ + unsigned long j = jiffies; + unsigned long j1; + + rsp->gp_start = j; + j1 = rcu_jiffies_till_stall_check(); + /* Record ->gp_start before ->jiffies_stall. */ + smp_store_release(&rsp->jiffies_stall, j + j1); /* ^^^ */ + rsp->jiffies_resched = j + j1 / 2; + rsp->n_force_qs_gpstart = READ_ONCE(rsp->n_force_qs); +} + +/* + * Convert a ->gp_state value to a character string. + */ +static const char *gp_state_getname(short gs) +{ + if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names)) + return "???"; + return gp_state_names[gs]; +} + +/* + * Complain about starvation of grace-period kthread. + */ +static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp) +{ + unsigned long gpa; + unsigned long j; + + j = jiffies; + gpa = READ_ONCE(rsp->gp_activity); + if (j - gpa > 2 * HZ) { + pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#lx ->cpu=%d\n", + rsp->name, j - gpa, + (long)rcu_seq_current(&rsp->gp_seq), + rsp->gp_flags, + gp_state_getname(rsp->gp_state), rsp->gp_state, + rsp->gp_kthread ? rsp->gp_kthread->state : ~0, + rsp->gp_kthread ? task_cpu(rsp->gp_kthread) : -1); + if (rsp->gp_kthread) { + pr_err("RCU grace-period kthread stack dump:\n"); + sched_show_task(rsp->gp_kthread); + wake_up_process(rsp->gp_kthread); + } + } +} + +/* + * Dump stacks of all tasks running on stalled CPUs. First try using + * NMIs, but fall back to manual remote stack tracing on architectures + * that don't support NMI-based stack dumps. The NMI-triggered stack + * traces are more accurate because they are printed by the target CPU. + */ +static void rcu_dump_cpu_stacks(struct rcu_state *rsp) +{ + int cpu; + unsigned long flags; + struct rcu_node *rnp; + + rcu_for_each_leaf_node(rsp, rnp) { + raw_spin_lock_irqsave_rcu_node(rnp, flags); + for_each_leaf_node_possible_cpu(rnp, cpu) + if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) + if (!trigger_single_cpu_backtrace(cpu)) + dump_cpu_task(cpu); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } +} + +/* + * If too much time has passed in the current grace period, and if + * so configured, go kick the relevant kthreads. + */ +static void rcu_stall_kick_kthreads(struct rcu_state *rsp) +{ + unsigned long j; + + if (!rcu_kick_kthreads) + return; + j = READ_ONCE(rsp->jiffies_kick_kthreads); + if (time_after(jiffies, j) && rsp->gp_kthread && + (rcu_gp_in_progress(rsp) || READ_ONCE(rsp->gp_flags))) { + WARN_ONCE(1, "Kicking %s grace-period kthread\n", rsp->name); + rcu_ftrace_dump(DUMP_ALL); + wake_up_process(rsp->gp_kthread); + WRITE_ONCE(rsp->jiffies_kick_kthreads, j + HZ); + } +} + +static void panic_on_rcu_stall(void) +{ + if (sysctl_panic_on_rcu_stall) + panic("RCU Stall\n"); +} + +static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gp_seq) +{ + int cpu; + unsigned long flags; + unsigned long gpa; + unsigned long j; + int ndetected = 0; + struct rcu_node *rnp = rcu_get_root(rsp); + long totqlen = 0; + + /* Kick and suppress, if so configured. */ + rcu_stall_kick_kthreads(rsp); + if (rcu_cpu_stall_suppress) + return; + + /* + * OK, time to rat on our buddy... + * See Documentation/RCU/stallwarn.txt for info on how to debug + * RCU CPU stall warnings. + */ + pr_err("INFO: %s detected stalls on CPUs/tasks:", rsp->name); + print_cpu_stall_info_begin(); + rcu_for_each_leaf_node(rsp, rnp) { + raw_spin_lock_irqsave_rcu_node(rnp, flags); + ndetected += rcu_print_task_stall(rnp); + if (rnp->qsmask != 0) { + for_each_leaf_node_possible_cpu(rnp, cpu) + if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) { + print_cpu_stall_info(rsp, cpu); + ndetected++; + } + } + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + + print_cpu_stall_info_end(); + for_each_possible_cpu(cpu) + totqlen += rcu_segcblist_n_cbs(&per_cpu_ptr(rsp->rda, + cpu)->cblist); + pr_cont("(detected by %d, t=%ld jiffies, g=%ld, q=%lu)\n", + smp_processor_id(), (long)(jiffies - rsp->gp_start), + (long)rcu_seq_current(&rsp->gp_seq), totqlen); + if (ndetected) { + rcu_dump_cpu_stacks(rsp); + + /* Complain about tasks blocking the grace period. */ + rcu_print_detail_task_stall(rsp); + } else { + if (rcu_seq_current(&rsp->gp_seq) != gp_seq) { + pr_err("INFO: Stall ended before state dump start\n"); + } else { + j = jiffies; + gpa = READ_ONCE(rsp->gp_activity); + pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n", + rsp->name, j - gpa, j, gpa, + jiffies_till_next_fqs, + rcu_get_root(rsp)->qsmask); + /* In this case, the current CPU might be at fault. */ + sched_show_task(current); + } + } + /* Rewrite if needed in case of slow consoles. */ + if (ULONG_CMP_GE(jiffies, READ_ONCE(rsp->jiffies_stall))) + WRITE_ONCE(rsp->jiffies_stall, + jiffies + 3 * rcu_jiffies_till_stall_check() + 3); + + rcu_check_gp_kthread_starvation(rsp); + + panic_on_rcu_stall(); + + force_quiescent_state(rsp); /* Kick them all. */ +} + +static void print_cpu_stall(struct rcu_state *rsp) +{ + int cpu; + unsigned long flags; + struct rcu_data *rdp = this_cpu_ptr(rsp->rda); + struct rcu_node *rnp = rcu_get_root(rsp); + long totqlen = 0; + + /* Kick and suppress, if so configured. */ + rcu_stall_kick_kthreads(rsp); + if (rcu_cpu_stall_suppress) + return; + + /* + * OK, time to rat on ourselves... + * See Documentation/RCU/stallwarn.txt for info on how to debug + * RCU CPU stall warnings. + */ + pr_err("INFO: %s self-detected stall on CPU", rsp->name); + print_cpu_stall_info_begin(); + raw_spin_lock_irqsave_rcu_node(rdp->mynode, flags); + print_cpu_stall_info(rsp, smp_processor_id()); + raw_spin_unlock_irqrestore_rcu_node(rdp->mynode, flags); + print_cpu_stall_info_end(); + for_each_possible_cpu(cpu) + totqlen += rcu_segcblist_n_cbs(&per_cpu_ptr(rsp->rda, + cpu)->cblist); + pr_cont(" (t=%lu jiffies g=%ld q=%lu)\n", + jiffies - rsp->gp_start, + (long)rcu_seq_current(&rsp->gp_seq), totqlen); + + rcu_check_gp_kthread_starvation(rsp); + + rcu_dump_cpu_stacks(rsp); + + raw_spin_lock_irqsave_rcu_node(rnp, flags); + /* Rewrite if needed in case of slow consoles. */ + if (ULONG_CMP_GE(jiffies, READ_ONCE(rsp->jiffies_stall))) + WRITE_ONCE(rsp->jiffies_stall, + jiffies + 3 * rcu_jiffies_till_stall_check() + 3); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + + panic_on_rcu_stall(); + + /* + * Attempt to revive the RCU machinery by forcing a context switch. + * + * A context switch would normally allow the RCU state machine to make + * progress and it could be we're stuck in kernel space without context + * switches for an entirely unreasonable amount of time. + */ + resched_cpu(smp_processor_id()); +} + +static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) +{ + unsigned long gs1; + unsigned long gs2; + unsigned long gps; + unsigned long j; + unsigned long jn; + unsigned long js; + struct rcu_node *rnp; + + if ((rcu_cpu_stall_suppress && !rcu_kick_kthreads) || + !rcu_gp_in_progress(rsp)) + return; + rcu_stall_kick_kthreads(rsp); + j = jiffies; + + /* + * Lots of memory barriers to reject false positives. + * + * The idea is to pick up rsp->gp_seq, then rsp->jiffies_stall, + * then rsp->gp_start, and finally another copy of rsp->gp_seq. + * These values are updated in the opposite order with memory + * barriers (or equivalent) during grace-period initialization + * and cleanup. Now, a false positive can occur if we get an new + * value of rsp->gp_start and a old value of rsp->jiffies_stall. + * But given the memory barriers, the only way that this can happen + * is if one grace period ends and another starts between these + * two fetches. This is detected by comparing the second fetch + * of rsp->gp_seq with the previous fetch from rsp->gp_seq. + * + * Given this check, comparisons of jiffies, rsp->jiffies_stall, + * and rsp->gp_start suffice to forestall false positives. + */ + gs1 = READ_ONCE(rsp->gp_seq); + smp_rmb(); /* Pick up ->gp_seq first... */ + js = READ_ONCE(rsp->jiffies_stall); + smp_rmb(); /* ...then ->jiffies_stall before the rest... */ + gps = READ_ONCE(rsp->gp_start); + smp_rmb(); /* ...and finally ->gp_start before ->gp_seq again. */ + gs2 = READ_ONCE(rsp->gp_seq); + if (gs1 != gs2 || + ULONG_CMP_LT(j, js) || + ULONG_CMP_GE(gps, js)) + return; /* No stall or GP completed since entering function. */ + rnp = rdp->mynode; + jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; + if (rcu_gp_in_progress(rsp) && + (READ_ONCE(rnp->qsmask) & rdp->grpmask) && + cmpxchg(&rsp->jiffies_stall, js, jn) == js) { + + /* We haven't checked in, so go dump stack. */ + print_cpu_stall(rsp); + + } else if (rcu_gp_in_progress(rsp) && + ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) && + cmpxchg(&rsp->jiffies_stall, js, jn) == js) { + + /* They had a few time units to dump stack, so complain. */ + print_other_cpu_stall(rsp, gs2); + } +} + +/** + * rcu_cpu_stall_reset - prevent further stall warnings in current grace period + * + * Set the stall-warning timeout way off into the future, thus preventing + * any RCU CPU stall-warning messages from appearing in the current set of + * RCU grace periods. + * + * The caller must disable hard irqs. + */ +void rcu_cpu_stall_reset(void) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + WRITE_ONCE(rsp->jiffies_stall, jiffies + ULONG_MAX / 2); +} + +/* Trace-event wrapper function for trace_rcu_future_grace_period. */ +static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, + unsigned long gp_seq_req, const char *s) +{ + trace_rcu_future_grace_period(rdp->rsp->name, rnp->gp_seq, gp_seq_req, + rnp->level, rnp->grplo, rnp->grphi, s); +} + +/* + * rcu_start_this_gp - Request the start of a particular grace period + * @rnp_start: The leaf node of the CPU from which to start. + * @rdp: The rcu_data corresponding to the CPU from which to start. + * @gp_seq_req: The gp_seq of the grace period to start. + * + * Start the specified grace period, as needed to handle newly arrived + * callbacks. The required future grace periods are recorded in each + * rcu_node structure's ->gp_seq_needed field. Returns true if there + * is reason to awaken the grace-period kthread. + * + * The caller must hold the specified rcu_node structure's ->lock, which + * is why the caller is responsible for waking the grace-period kthread. + * + * Returns true if the GP thread needs to be awakened else false. + */ +static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp, + unsigned long gp_seq_req) +{ + bool ret = false; + struct rcu_state *rsp = rdp->rsp; + struct rcu_node *rnp; + + /* + * Use funnel locking to either acquire the root rcu_node + * structure's lock or bail out if the need for this grace period + * has already been recorded -- or if that grace period has in + * fact already started. If there is already a grace period in + * progress in a non-leaf node, no recording is needed because the + * end of the grace period will scan the leaf rcu_node structures. + * Note that rnp_start->lock must not be released. + */ + raw_lockdep_assert_held_rcu_node(rnp_start); + trace_rcu_this_gp(rnp_start, rdp, gp_seq_req, TPS("Startleaf")); + for (rnp = rnp_start; 1; rnp = rnp->parent) { + if (rnp != rnp_start) + raw_spin_lock_rcu_node(rnp); + if (ULONG_CMP_GE(rnp->gp_seq_needed, gp_seq_req) || + rcu_seq_started(&rnp->gp_seq, gp_seq_req) || + (rnp != rnp_start && + rcu_seq_state(rcu_seq_current(&rnp->gp_seq)))) { + trace_rcu_this_gp(rnp, rdp, gp_seq_req, + TPS("Prestarted")); + goto unlock_out; + } + rnp->gp_seq_needed = gp_seq_req; + if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) { + /* + * We just marked the leaf or internal node, and a + * grace period is in progress, which means that + * rcu_gp_cleanup() will see the marking. Bail to + * reduce contention. + */ + trace_rcu_this_gp(rnp_start, rdp, gp_seq_req, + TPS("Startedleaf")); + goto unlock_out; + } + if (rnp != rnp_start && rnp->parent != NULL) + raw_spin_unlock_rcu_node(rnp); + if (!rnp->parent) + break; /* At root, and perhaps also leaf. */ + } + + /* If GP already in progress, just leave, otherwise start one. */ + if (rcu_gp_in_progress(rsp)) { + trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedleafroot")); + goto unlock_out; + } + trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedroot")); + WRITE_ONCE(rsp->gp_flags, rsp->gp_flags | RCU_GP_FLAG_INIT); + rsp->gp_req_activity = jiffies; + if (!rsp->gp_kthread) { + trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("NoGPkthread")); + goto unlock_out; + } + trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gp_seq), TPS("newreq")); + ret = true; /* Caller must wake GP kthread. */ +unlock_out: + /* Push furthest requested GP to leaf node and rcu_data structure. */ + if (ULONG_CMP_LT(gp_seq_req, rnp->gp_seq_needed)) { + rnp_start->gp_seq_needed = rnp->gp_seq_needed; + rdp->gp_seq_needed = rnp->gp_seq_needed; + } + if (rnp != rnp_start) + raw_spin_unlock_rcu_node(rnp); + return ret; +} + +/* + * Clean up any old requests for the just-ended grace period. Also return + * whether any additional grace periods have been requested. + */ +static bool rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) +{ + bool needmore; + struct rcu_data *rdp = this_cpu_ptr(rsp->rda); + + needmore = ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed); + if (!needmore) + rnp->gp_seq_needed = rnp->gp_seq; /* Avoid counter wrap. */ + trace_rcu_this_gp(rnp, rdp, rnp->gp_seq, + needmore ? TPS("CleanupMore") : TPS("Cleanup")); + return needmore; +} + +/* + * Awaken the grace-period kthread. Don't do a self-awaken (unless in + * an interrupt or softirq handler), and don't bother awakening when there + * is nothing for the grace-period kthread to do (as in several CPUs raced + * to awaken, and we lost), and finally don't try to awaken a kthread that + * has not yet been created. If all those checks are passed, track some + * debug information and awaken. + * + * So why do the self-wakeup when in an interrupt or softirq handler + * in the grace-period kthread's context? Because the kthread might have + * been interrupted just as it was going to sleep, and just after the final + * pre-sleep check of the awaken condition. In this case, a wakeup really + * is required, and is therefore supplied. + */ +static void rcu_gp_kthread_wake(struct rcu_state *rsp) +{ + if ((current == rsp->gp_kthread && + !in_interrupt() && !in_serving_softirq()) || + !READ_ONCE(rsp->gp_flags) || + !rsp->gp_kthread) + return; + swake_up_one(&rsp->gp_wq); +} + +/* + * If there is room, assign a ->gp_seq number to any callbacks on this + * CPU that have not already been assigned. Also accelerate any callbacks + * that were previously assigned a ->gp_seq number that has since proven + * to be too conservative, which can happen if callbacks get assigned a + * ->gp_seq number while RCU is idle, but with reference to a non-root + * rcu_node structure. This function is idempotent, so it does not hurt + * to call it repeatedly. Returns an flag saying that we should awaken + * the RCU grace-period kthread. + * + * The caller must hold rnp->lock with interrupts disabled. + */ +static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, + struct rcu_data *rdp) +{ + unsigned long gp_seq_req; + bool ret = false; + + raw_lockdep_assert_held_rcu_node(rnp); + + /* If no pending (not yet ready to invoke) callbacks, nothing to do. */ + if (!rcu_segcblist_pend_cbs(&rdp->cblist)) + return false; + + /* + * Callbacks are often registered with incomplete grace-period + * information. Something about the fact that getting exact + * information requires acquiring a global lock... RCU therefore + * makes a conservative estimate of the grace period number at which + * a given callback will become ready to invoke. The following + * code checks this estimate and improves it when possible, thus + * accelerating callback invocation to an earlier grace-period + * number. + */ + gp_seq_req = rcu_seq_snap(&rsp->gp_seq); + if (rcu_segcblist_accelerate(&rdp->cblist, gp_seq_req)) + ret = rcu_start_this_gp(rnp, rdp, gp_seq_req); + + /* Trace depending on how much we were able to accelerate. */ + if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL)) + trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("AccWaitCB")); + else + trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("AccReadyCB")); + return ret; +} + +/* + * Similar to rcu_accelerate_cbs(), but does not require that the leaf + * rcu_node structure's ->lock be held. It consults the cached value + * of ->gp_seq_needed in the rcu_data structure, and if that indicates + * that a new grace-period request be made, invokes rcu_accelerate_cbs() + * while holding the leaf rcu_node structure's ->lock. + */ +static void rcu_accelerate_cbs_unlocked(struct rcu_state *rsp, + struct rcu_node *rnp, + struct rcu_data *rdp) +{ + unsigned long c; + bool needwake; + + lockdep_assert_irqs_disabled(); + c = rcu_seq_snap(&rsp->gp_seq); + if (!rdp->gpwrap && ULONG_CMP_GE(rdp->gp_seq_needed, c)) { + /* Old request still live, so mark recent callbacks. */ + (void)rcu_segcblist_accelerate(&rdp->cblist, c); + return; + } + raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ + needwake = rcu_accelerate_cbs(rsp, rnp, rdp); + raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ + if (needwake) + rcu_gp_kthread_wake(rsp); +} + +/* + * Move any callbacks whose grace period has completed to the + * RCU_DONE_TAIL sublist, then compact the remaining sublists and + * assign ->gp_seq numbers to any callbacks in the RCU_NEXT_TAIL + * sublist. This function is idempotent, so it does not hurt to + * invoke it repeatedly. As long as it is not invoked -too- often... + * Returns true if the RCU grace-period kthread needs to be awakened. + * + * The caller must hold rnp->lock with interrupts disabled. + */ +static bool rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp, + struct rcu_data *rdp) +{ + raw_lockdep_assert_held_rcu_node(rnp); + + /* If no pending (not yet ready to invoke) callbacks, nothing to do. */ + if (!rcu_segcblist_pend_cbs(&rdp->cblist)) + return false; + + /* + * Find all callbacks whose ->gp_seq numbers indicate that they + * are ready to invoke, and put them into the RCU_DONE_TAIL sublist. + */ + rcu_segcblist_advance(&rdp->cblist, rnp->gp_seq); + + /* Classify any remaining callbacks. */ + return rcu_accelerate_cbs(rsp, rnp, rdp); +} + +/* + * Update CPU-local rcu_data state to record the beginnings and ends of + * grace periods. The caller must hold the ->lock of the leaf rcu_node + * structure corresponding to the current CPU, and must have irqs disabled. + * Returns true if the grace-period kthread needs to be awakened. + */ +static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, + struct rcu_data *rdp) +{ + bool ret; + bool need_gp; + + raw_lockdep_assert_held_rcu_node(rnp); + + if (rdp->gp_seq == rnp->gp_seq) + return false; /* Nothing to do. */ + + /* Handle the ends of any preceding grace periods first. */ + if (rcu_seq_completed_gp(rdp->gp_seq, rnp->gp_seq) || + unlikely(READ_ONCE(rdp->gpwrap))) { + ret = rcu_advance_cbs(rsp, rnp, rdp); /* Advance callbacks. */ + trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("cpuend")); + } else { + ret = rcu_accelerate_cbs(rsp, rnp, rdp); /* Recent callbacks. */ + } + + /* Now handle the beginnings of any new-to-this-CPU grace periods. */ + if (rcu_seq_new_gp(rdp->gp_seq, rnp->gp_seq) || + unlikely(READ_ONCE(rdp->gpwrap))) { + /* + * If the current grace period is waiting for this CPU, + * set up to detect a quiescent state, otherwise don't + * go looking for one. + */ + trace_rcu_grace_period(rsp->name, rnp->gp_seq, TPS("cpustart")); + need_gp = !!(rnp->qsmask & rdp->grpmask); + rdp->cpu_no_qs.b.norm = need_gp; + rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_dynticks.rcu_qs_ctr); + rdp->core_needs_qs = need_gp; + zero_cpu_stall_ticks(rdp); + } + rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */ + if (ULONG_CMP_GE(rnp->gp_seq_needed, rdp->gp_seq_needed) || rdp->gpwrap) + rdp->gp_seq_needed = rnp->gp_seq_needed; + WRITE_ONCE(rdp->gpwrap, false); + rcu_gpnum_ovf(rnp, rdp); + return ret; +} + +static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp) +{ + unsigned long flags; + bool needwake; + struct rcu_node *rnp; + + local_irq_save(flags); + rnp = rdp->mynode; + if ((rdp->gp_seq == rcu_seq_current(&rnp->gp_seq) && + !unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */ + !raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */ + local_irq_restore(flags); + return; + } + needwake = __note_gp_changes(rsp, rnp, rdp); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + if (needwake) + rcu_gp_kthread_wake(rsp); +} + +static void rcu_gp_slow(struct rcu_state *rsp, int delay) +{ + if (delay > 0 && + !(rcu_seq_ctr(rsp->gp_seq) % + (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay))) + schedule_timeout_uninterruptible(delay); +} + +/* + * Initialize a new grace period. Return false if no grace period required. + */ +static bool rcu_gp_init(struct rcu_state *rsp) +{ + unsigned long flags; + unsigned long oldmask; + unsigned long mask; + struct rcu_data *rdp; + struct rcu_node *rnp = rcu_get_root(rsp); + + WRITE_ONCE(rsp->gp_activity, jiffies); + raw_spin_lock_irq_rcu_node(rnp); + if (!READ_ONCE(rsp->gp_flags)) { + /* Spurious wakeup, tell caller to go back to sleep. */ + raw_spin_unlock_irq_rcu_node(rnp); + return false; + } + WRITE_ONCE(rsp->gp_flags, 0); /* Clear all flags: New grace period. */ + + if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) { + /* + * Grace period already in progress, don't start another. + * Not supposed to be able to happen. + */ + raw_spin_unlock_irq_rcu_node(rnp); + return false; + } + + /* Advance to a new grace period and initialize state. */ + record_gp_stall_check_time(rsp); + /* Record GP times before starting GP, hence rcu_seq_start(). */ + rcu_seq_start(&rsp->gp_seq); + trace_rcu_grace_period(rsp->name, rsp->gp_seq, TPS("start")); + raw_spin_unlock_irq_rcu_node(rnp); + + /* + * Apply per-leaf buffered online and offline operations to the + * rcu_node tree. Note that this new grace period need not wait + * for subsequent online CPUs, and that quiescent-state forcing + * will handle subsequent offline CPUs. + */ + rsp->gp_state = RCU_GP_ONOFF; + rcu_for_each_leaf_node(rsp, rnp) { + spin_lock(&rsp->ofl_lock); + raw_spin_lock_irq_rcu_node(rnp); + if (rnp->qsmaskinit == rnp->qsmaskinitnext && + !rnp->wait_blkd_tasks) { + /* Nothing to do on this leaf rcu_node structure. */ + raw_spin_unlock_irq_rcu_node(rnp); + spin_unlock(&rsp->ofl_lock); + continue; + } + + /* Record old state, apply changes to ->qsmaskinit field. */ + oldmask = rnp->qsmaskinit; + rnp->qsmaskinit = rnp->qsmaskinitnext; + + /* If zero-ness of ->qsmaskinit changed, propagate up tree. */ + if (!oldmask != !rnp->qsmaskinit) { + if (!oldmask) { /* First online CPU for rcu_node. */ + if (!rnp->wait_blkd_tasks) /* Ever offline? */ + rcu_init_new_rnp(rnp); + } else if (rcu_preempt_has_tasks(rnp)) { + rnp->wait_blkd_tasks = true; /* blocked tasks */ + } else { /* Last offline CPU and can propagate. */ + rcu_cleanup_dead_rnp(rnp); + } + } + + /* + * If all waited-on tasks from prior grace period are + * done, and if all this rcu_node structure's CPUs are + * still offline, propagate up the rcu_node tree and + * clear ->wait_blkd_tasks. Otherwise, if one of this + * rcu_node structure's CPUs has since come back online, + * simply clear ->wait_blkd_tasks. + */ + if (rnp->wait_blkd_tasks && + (!rcu_preempt_has_tasks(rnp) || rnp->qsmaskinit)) { + rnp->wait_blkd_tasks = false; + if (!rnp->qsmaskinit) + rcu_cleanup_dead_rnp(rnp); + } + + raw_spin_unlock_irq_rcu_node(rnp); + spin_unlock(&rsp->ofl_lock); + } + rcu_gp_slow(rsp, gp_preinit_delay); /* Races with CPU hotplug. */ + + /* + * Set the quiescent-state-needed bits in all the rcu_node + * structures for all currently online CPUs in breadth-first order, + * starting from the root rcu_node structure, relying on the layout + * of the tree within the rsp->node[] array. Note that other CPUs + * will access only the leaves of the hierarchy, thus seeing that no + * grace period is in progress, at least until the corresponding + * leaf node has been initialized. + * + * The grace period cannot complete until the initialization + * process finishes, because this kthread handles both. + */ + rsp->gp_state = RCU_GP_INIT; + rcu_for_each_node_breadth_first(rsp, rnp) { + rcu_gp_slow(rsp, gp_init_delay); + raw_spin_lock_irqsave_rcu_node(rnp, flags); + rdp = this_cpu_ptr(rsp->rda); + rcu_preempt_check_blocked_tasks(rsp, rnp); + rnp->qsmask = rnp->qsmaskinit; + WRITE_ONCE(rnp->gp_seq, rsp->gp_seq); + if (rnp == rdp->mynode) + (void)__note_gp_changes(rsp, rnp, rdp); + rcu_preempt_boost_start_gp(rnp); + trace_rcu_grace_period_init(rsp->name, rnp->gp_seq, + rnp->level, rnp->grplo, + rnp->grphi, rnp->qsmask); + /* Quiescent states for tasks on any now-offline CPUs. */ + mask = rnp->qsmask & ~rnp->qsmaskinitnext; + rnp->rcu_gp_init_mask = mask; + if ((mask || rnp->wait_blkd_tasks) && rcu_is_leaf_node(rnp)) + rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags); + else + raw_spin_unlock_irq_rcu_node(rnp); + cond_resched_tasks_rcu_qs(); + WRITE_ONCE(rsp->gp_activity, jiffies); + } + + return true; +} + +/* + * Helper function for swait_event_idle_exclusive() wakeup at force-quiescent-state + * time. + */ +static bool rcu_gp_fqs_check_wake(struct rcu_state *rsp, int *gfp) +{ + struct rcu_node *rnp = rcu_get_root(rsp); + + /* Someone like call_rcu() requested a force-quiescent-state scan. */ + *gfp = READ_ONCE(rsp->gp_flags); + if (*gfp & RCU_GP_FLAG_FQS) + return true; + + /* The current grace period has completed. */ + if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp)) + return true; + + return false; +} + +/* + * Do one round of quiescent-state forcing. + */ +static void rcu_gp_fqs(struct rcu_state *rsp, bool first_time) +{ + struct rcu_node *rnp = rcu_get_root(rsp); + + WRITE_ONCE(rsp->gp_activity, jiffies); + rsp->n_force_qs++; + if (first_time) { + /* Collect dyntick-idle snapshots. */ + force_qs_rnp(rsp, dyntick_save_progress_counter); + } else { + /* Handle dyntick-idle and offline CPUs. */ + force_qs_rnp(rsp, rcu_implicit_dynticks_qs); + } + /* Clear flag to prevent immediate re-entry. */ + if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { + raw_spin_lock_irq_rcu_node(rnp); + WRITE_ONCE(rsp->gp_flags, + READ_ONCE(rsp->gp_flags) & ~RCU_GP_FLAG_FQS); + raw_spin_unlock_irq_rcu_node(rnp); + } +} + +/* + * Clean up after the old grace period. + */ +static void rcu_gp_cleanup(struct rcu_state *rsp) +{ + unsigned long gp_duration; + bool needgp = false; + unsigned long new_gp_seq; + struct rcu_data *rdp; + struct rcu_node *rnp = rcu_get_root(rsp); + struct swait_queue_head *sq; + + WRITE_ONCE(rsp->gp_activity, jiffies); + raw_spin_lock_irq_rcu_node(rnp); + gp_duration = jiffies - rsp->gp_start; + if (gp_duration > rsp->gp_max) + rsp->gp_max = gp_duration; + + /* + * We know the grace period is complete, but to everyone else + * it appears to still be ongoing. But it is also the case + * that to everyone else it looks like there is nothing that + * they can do to advance the grace period. It is therefore + * safe for us to drop the lock in order to mark the grace + * period as completed in all of the rcu_node structures. + */ + raw_spin_unlock_irq_rcu_node(rnp); + + /* + * Propagate new ->gp_seq value to rcu_node structures so that + * other CPUs don't have to wait until the start of the next grace + * period to process their callbacks. This also avoids some nasty + * RCU grace-period initialization races by forcing the end of + * the current grace period to be completely recorded in all of + * the rcu_node structures before the beginning of the next grace + * period is recorded in any of the rcu_node structures. + */ + new_gp_seq = rsp->gp_seq; + rcu_seq_end(&new_gp_seq); + rcu_for_each_node_breadth_first(rsp, rnp) { + raw_spin_lock_irq_rcu_node(rnp); + if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp))) + dump_blkd_tasks(rsp, rnp, 10); + WARN_ON_ONCE(rnp->qsmask); + WRITE_ONCE(rnp->gp_seq, new_gp_seq); + rdp = this_cpu_ptr(rsp->rda); + if (rnp == rdp->mynode) + needgp = __note_gp_changes(rsp, rnp, rdp) || needgp; + /* smp_mb() provided by prior unlock-lock pair. */ + needgp = rcu_future_gp_cleanup(rsp, rnp) || needgp; + sq = rcu_nocb_gp_get(rnp); + raw_spin_unlock_irq_rcu_node(rnp); + rcu_nocb_gp_cleanup(sq); + cond_resched_tasks_rcu_qs(); + WRITE_ONCE(rsp->gp_activity, jiffies); + rcu_gp_slow(rsp, gp_cleanup_delay); + } + rnp = rcu_get_root(rsp); + raw_spin_lock_irq_rcu_node(rnp); /* GP before rsp->gp_seq update. */ + + /* Declare grace period done. */ + rcu_seq_end(&rsp->gp_seq); + trace_rcu_grace_period(rsp->name, rsp->gp_seq, TPS("end")); + rsp->gp_state = RCU_GP_IDLE; + /* Check for GP requests since above loop. */ + rdp = this_cpu_ptr(rsp->rda); + if (!needgp && ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed)) { + trace_rcu_this_gp(rnp, rdp, rnp->gp_seq_needed, + TPS("CleanupMore")); + needgp = true; + } + /* Advance CBs to reduce false positives below. */ + if (!rcu_accelerate_cbs(rsp, rnp, rdp) && needgp) { + WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT); + rsp->gp_req_activity = jiffies; + trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gp_seq), + TPS("newreq")); + } else { + WRITE_ONCE(rsp->gp_flags, rsp->gp_flags & RCU_GP_FLAG_INIT); + } + raw_spin_unlock_irq_rcu_node(rnp); +} + +/* + * Body of kthread that handles grace periods. + */ +static int __noreturn rcu_gp_kthread(void *arg) +{ + bool first_gp_fqs; + int gf; + unsigned long j; + int ret; + struct rcu_state *rsp = arg; + struct rcu_node *rnp = rcu_get_root(rsp); + + rcu_bind_gp_kthread(); + for (;;) { + + /* Handle grace-period start. */ + for (;;) { + trace_rcu_grace_period(rsp->name, + READ_ONCE(rsp->gp_seq), + TPS("reqwait")); + rsp->gp_state = RCU_GP_WAIT_GPS; + swait_event_idle_exclusive(rsp->gp_wq, READ_ONCE(rsp->gp_flags) & + RCU_GP_FLAG_INIT); + rsp->gp_state = RCU_GP_DONE_GPS; + /* Locking provides needed memory barrier. */ + if (rcu_gp_init(rsp)) + break; + cond_resched_tasks_rcu_qs(); + WRITE_ONCE(rsp->gp_activity, jiffies); + WARN_ON(signal_pending(current)); + trace_rcu_grace_period(rsp->name, + READ_ONCE(rsp->gp_seq), + TPS("reqwaitsig")); + } + + /* Handle quiescent-state forcing. */ + first_gp_fqs = true; + j = jiffies_till_first_fqs; + ret = 0; + for (;;) { + if (!ret) { + rsp->jiffies_force_qs = jiffies + j; + WRITE_ONCE(rsp->jiffies_kick_kthreads, + jiffies + 3 * j); + } + trace_rcu_grace_period(rsp->name, + READ_ONCE(rsp->gp_seq), + TPS("fqswait")); + rsp->gp_state = RCU_GP_WAIT_FQS; + ret = swait_event_idle_timeout_exclusive(rsp->gp_wq, + rcu_gp_fqs_check_wake(rsp, &gf), j); + rsp->gp_state = RCU_GP_DOING_FQS; + /* Locking provides needed memory barriers. */ + /* If grace period done, leave loop. */ + if (!READ_ONCE(rnp->qsmask) && + !rcu_preempt_blocked_readers_cgp(rnp)) + break; + /* If time for quiescent-state forcing, do it. */ + if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) || + (gf & RCU_GP_FLAG_FQS)) { + trace_rcu_grace_period(rsp->name, + READ_ONCE(rsp->gp_seq), + TPS("fqsstart")); + rcu_gp_fqs(rsp, first_gp_fqs); + first_gp_fqs = false; + trace_rcu_grace_period(rsp->name, + READ_ONCE(rsp->gp_seq), + TPS("fqsend")); + cond_resched_tasks_rcu_qs(); + WRITE_ONCE(rsp->gp_activity, jiffies); + ret = 0; /* Force full wait till next FQS. */ + j = jiffies_till_next_fqs; + } else { + /* Deal with stray signal. */ + cond_resched_tasks_rcu_qs(); + WRITE_ONCE(rsp->gp_activity, jiffies); + WARN_ON(signal_pending(current)); + trace_rcu_grace_period(rsp->name, + READ_ONCE(rsp->gp_seq), + TPS("fqswaitsig")); + ret = 1; /* Keep old FQS timing. */ + j = jiffies; + if (time_after(jiffies, rsp->jiffies_force_qs)) + j = 1; + else + j = rsp->jiffies_force_qs - j; + } + } + + /* Handle grace-period end. */ + rsp->gp_state = RCU_GP_CLEANUP; + rcu_gp_cleanup(rsp); + rsp->gp_state = RCU_GP_CLEANED; + } +} + +/* + * Report a full set of quiescent states to the specified rcu_state data + * structure. Invoke rcu_gp_kthread_wake() to awaken the grace-period + * kthread if another grace period is required. Whether we wake + * the grace-period kthread or it awakens itself for the next round + * of quiescent-state forcing, that kthread will clean up after the + * just-completed grace period. Note that the caller must hold rnp->lock, + * which is released before return. + */ +static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) + __releases(rcu_get_root(rsp)->lock) +{ + raw_lockdep_assert_held_rcu_node(rcu_get_root(rsp)); + WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); + WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS); + raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(rsp), flags); + rcu_gp_kthread_wake(rsp); +} + +/* + * Similar to rcu_report_qs_rdp(), for which it is a helper function. + * Allows quiescent states for a group of CPUs to be reported at one go + * to the specified rcu_node structure, though all the CPUs in the group + * must be represented by the same rcu_node structure (which need not be a + * leaf rcu_node structure, though it often will be). The gps parameter + * is the grace-period snapshot, which means that the quiescent states + * are valid only if rnp->gp_seq is equal to gps. That structure's lock + * must be held upon entry, and it is released before return. + * + * As a special case, if mask is zero, the bit-already-cleared check is + * disabled. This allows propagating quiescent state due to resumed tasks + * during grace-period initialization. + */ +static void +rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, + struct rcu_node *rnp, unsigned long gps, unsigned long flags) + __releases(rnp->lock) +{ + unsigned long oldmask = 0; + struct rcu_node *rnp_c; + + raw_lockdep_assert_held_rcu_node(rnp); + + /* Walk up the rcu_node hierarchy. */ + for (;;) { + if ((!(rnp->qsmask & mask) && mask) || rnp->gp_seq != gps) { + + /* + * Our bit has already been cleared, or the + * relevant grace period is already over, so done. + */ + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */ + WARN_ON_ONCE(!rcu_is_leaf_node(rnp) && + rcu_preempt_blocked_readers_cgp(rnp)); + rnp->qsmask &= ~mask; + trace_rcu_quiescent_state_report(rsp->name, rnp->gp_seq, + mask, rnp->qsmask, rnp->level, + rnp->grplo, rnp->grphi, + !!rnp->gp_tasks); + if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { + + /* Other bits still set at this level, so done. */ + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + rnp->completedqs = rnp->gp_seq; + mask = rnp->grpmask; + if (rnp->parent == NULL) { + + /* No more levels. Exit loop holding root lock. */ + + break; + } + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + rnp_c = rnp; + rnp = rnp->parent; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + oldmask = rnp_c->qsmask; + } + + /* + * Get here if we are the last CPU to pass through a quiescent + * state for this grace period. Invoke rcu_report_qs_rsp() + * to clean up and start the next grace period if one is needed. + */ + rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ +} + +/* + * Record a quiescent state for all tasks that were previously queued + * on the specified rcu_node structure and that were blocking the current + * RCU grace period. The caller must hold the specified rnp->lock with + * irqs disabled, and this lock is released upon return, but irqs remain + * disabled. + */ +static void __maybe_unused +rcu_report_unblock_qs_rnp(struct rcu_state *rsp, + struct rcu_node *rnp, unsigned long flags) + __releases(rnp->lock) +{ + unsigned long gps; + unsigned long mask; + struct rcu_node *rnp_p; + + raw_lockdep_assert_held_rcu_node(rnp); + if (WARN_ON_ONCE(rcu_state_p == &rcu_sched_state) || + WARN_ON_ONCE(rsp != rcu_state_p) || + WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)) || + rnp->qsmask != 0) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; /* Still need more quiescent states! */ + } + + rnp->completedqs = rnp->gp_seq; + rnp_p = rnp->parent; + if (rnp_p == NULL) { + /* + * Only one rcu_node structure in the tree, so don't + * try to report up to its nonexistent parent! + */ + rcu_report_qs_rsp(rsp, flags); + return; + } + + /* Report up the rest of the hierarchy, tracking current ->gp_seq. */ + gps = rnp->gp_seq; + mask = rnp->grpmask; + raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ + raw_spin_lock_rcu_node(rnp_p); /* irqs already disabled. */ + rcu_report_qs_rnp(mask, rsp, rnp_p, gps, flags); +} + +/* + * Record a quiescent state for the specified CPU to that CPU's rcu_data + * structure. This must be called from the specified CPU. + */ +static void +rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) +{ + unsigned long flags; + unsigned long mask; + bool needwake; + struct rcu_node *rnp; + + rnp = rdp->mynode; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq || + rdp->gpwrap) { + + /* + * The grace period in which this quiescent state was + * recorded has ended, so don't report it upwards. + * We will instead need a new quiescent state that lies + * within the current grace period. + */ + rdp->cpu_no_qs.b.norm = true; /* need qs for new gp. */ + rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_dynticks.rcu_qs_ctr); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + mask = rdp->grpmask; + if ((rnp->qsmask & mask) == 0) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } else { + rdp->core_needs_qs = false; + + /* + * This GP can't end until cpu checks in, so all of our + * callbacks can be processed during the next GP. + */ + needwake = rcu_accelerate_cbs(rsp, rnp, rdp); + + rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags); + /* ^^^ Released rnp->lock */ + if (needwake) + rcu_gp_kthread_wake(rsp); + } +} + +/* + * Check to see if there is a new grace period of which this CPU + * is not yet aware, and if so, set up local rcu_data state for it. + * Otherwise, see if this CPU has just passed through its first + * quiescent state for this grace period, and record that fact if so. + */ +static void +rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) +{ + /* Check for grace-period ends and beginnings. */ + note_gp_changes(rsp, rdp); + + /* + * Does this CPU still need to do its part for current grace period? + * If no, return and let the other CPUs do their part as well. + */ + if (!rdp->core_needs_qs) + return; + + /* + * Was there a quiescent state since the beginning of the grace + * period? If no, then exit and wait for the next call. + */ + if (rdp->cpu_no_qs.b.norm) + return; + + /* + * Tell RCU we are done (but rcu_report_qs_rdp() will be the + * judge of that). + */ + rcu_report_qs_rdp(rdp->cpu, rsp, rdp); +} + +/* + * Trace the fact that this CPU is going offline. + */ +static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) +{ + RCU_TRACE(bool blkd;) + RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda);) + RCU_TRACE(struct rcu_node *rnp = rdp->mynode;) + + if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) + return; + + RCU_TRACE(blkd = !!(rnp->qsmask & rdp->grpmask);) + trace_rcu_grace_period(rsp->name, rnp->gp_seq, + blkd ? TPS("cpuofl") : TPS("cpuofl-bgp")); +} + +/* + * All CPUs for the specified rcu_node structure have gone offline, + * and all tasks that were preempted within an RCU read-side critical + * section while running on one of those CPUs have since exited their RCU + * read-side critical section. Some other CPU is reporting this fact with + * the specified rcu_node structure's ->lock held and interrupts disabled. + * This function therefore goes up the tree of rcu_node structures, + * clearing the corresponding bits in the ->qsmaskinit fields. Note that + * the leaf rcu_node structure's ->qsmaskinit field has already been + * updated. + * + * This function does check that the specified rcu_node structure has + * all CPUs offline and no blocked tasks, so it is OK to invoke it + * prematurely. That said, invoking it after the fact will cost you + * a needless lock acquisition. So once it has done its work, don't + * invoke it again. + */ +static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf) +{ + long mask; + struct rcu_node *rnp = rnp_leaf; + + raw_lockdep_assert_held_rcu_node(rnp_leaf); + if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || + WARN_ON_ONCE(rnp_leaf->qsmaskinit) || + WARN_ON_ONCE(rcu_preempt_has_tasks(rnp_leaf))) + return; + for (;;) { + mask = rnp->grpmask; + rnp = rnp->parent; + if (!rnp) + break; + raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ + rnp->qsmaskinit &= ~mask; + /* Between grace periods, so better already be zero! */ + WARN_ON_ONCE(rnp->qsmask); + if (rnp->qsmaskinit) { + raw_spin_unlock_rcu_node(rnp); + /* irqs remain disabled. */ + return; + } + raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ + } +} + +/* + * The CPU has been completely removed, and some other CPU is reporting + * this fact from process context. Do the remainder of the cleanup. + * There can only be one CPU hotplug operation at a time, so no need for + * explicit locking. + */ +static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) +{ + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ + + if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) + return; + + /* Adjust any no-longer-needed kthreads. */ + rcu_boost_kthread_setaffinity(rnp, -1); +} + +/* + * Invoke any RCU callbacks that have made it to the end of their grace + * period. Thottle as specified by rdp->blimit. + */ +static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) +{ + unsigned long flags; + struct rcu_head *rhp; + struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl); + long bl, count; + + /* If no callbacks are ready, just return. */ + if (!rcu_segcblist_ready_cbs(&rdp->cblist)) { + trace_rcu_batch_start(rsp->name, + rcu_segcblist_n_lazy_cbs(&rdp->cblist), + rcu_segcblist_n_cbs(&rdp->cblist), 0); + trace_rcu_batch_end(rsp->name, 0, + !rcu_segcblist_empty(&rdp->cblist), + need_resched(), is_idle_task(current), + rcu_is_callbacks_kthread()); + return; + } + + /* + * Extract the list of ready callbacks, disabling to prevent + * races with call_rcu() from interrupt handlers. Leave the + * callback counts, as rcu_barrier() needs to be conservative. + */ + local_irq_save(flags); + WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); + bl = rdp->blimit; + trace_rcu_batch_start(rsp->name, rcu_segcblist_n_lazy_cbs(&rdp->cblist), + rcu_segcblist_n_cbs(&rdp->cblist), bl); + rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl); + local_irq_restore(flags); + + /* Invoke callbacks. */ + rhp = rcu_cblist_dequeue(&rcl); + for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) { + debug_rcu_head_unqueue(rhp); + if (__rcu_reclaim(rsp->name, rhp)) + rcu_cblist_dequeued_lazy(&rcl); + /* + * Stop only if limit reached and CPU has something to do. + * Note: The rcl structure counts down from zero. + */ + if (-rcl.len >= bl && + (need_resched() || + (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) + break; + } + + local_irq_save(flags); + count = -rcl.len; + trace_rcu_batch_end(rsp->name, count, !!rcl.head, need_resched(), + is_idle_task(current), rcu_is_callbacks_kthread()); + + /* Update counts and requeue any remaining callbacks. */ + rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl); + smp_mb(); /* List handling before counting for rcu_barrier(). */ + rcu_segcblist_insert_count(&rdp->cblist, &rcl); + + /* Reinstate batch limit if we have worked down the excess. */ + count = rcu_segcblist_n_cbs(&rdp->cblist); + if (rdp->blimit == LONG_MAX && count <= qlowmark) + rdp->blimit = blimit; + + /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ + if (count == 0 && rdp->qlen_last_fqs_check != 0) { + rdp->qlen_last_fqs_check = 0; + rdp->n_force_qs_snap = rsp->n_force_qs; + } else if (count < rdp->qlen_last_fqs_check - qhimark) + rdp->qlen_last_fqs_check = count; + + /* + * The following usually indicates a double call_rcu(). To track + * this down, try building with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y. + */ + WARN_ON_ONCE(rcu_segcblist_empty(&rdp->cblist) != (count == 0)); + + local_irq_restore(flags); + + /* Re-invoke RCU core processing if there are callbacks remaining. */ + if (rcu_segcblist_ready_cbs(&rdp->cblist)) + invoke_rcu_core(); +} + +/* + * Check to see if this CPU is in a non-context-switch quiescent state + * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). + * Also schedule RCU core processing. + * + * This function must be called from hardirq context. It is normally + * invoked from the scheduling-clock interrupt. + */ +void rcu_check_callbacks(int user) +{ + trace_rcu_utilization(TPS("Start scheduler-tick")); + increment_cpu_stall_ticks(); + if (user || rcu_is_cpu_rrupt_from_idle()) { + + /* + * Get here if this CPU took its interrupt from user + * mode or from the idle loop, and if this is not a + * nested interrupt. In this case, the CPU is in + * a quiescent state, so note it. + * + * No memory barrier is required here because both + * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local + * variables that other CPUs neither access nor modify, + * at least not while the corresponding CPU is online. + */ + + rcu_sched_qs(); + rcu_bh_qs(); + rcu_note_voluntary_context_switch(current); + + } else if (!in_softirq()) { + + /* + * Get here if this CPU did not take its interrupt from + * softirq, in other words, if it is not interrupting + * a rcu_bh read-side critical section. This is an _bh + * critical section, so note it. + */ + + rcu_bh_qs(); + } + rcu_preempt_check_callbacks(); + /* The load-acquire pairs with the store-release setting to true. */ + if (smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) { + /* Idle and userspace execution already are quiescent states. */ + if (!rcu_is_cpu_rrupt_from_idle() && !user) { + set_tsk_need_resched(current); + set_preempt_need_resched(); + } + __this_cpu_write(rcu_dynticks.rcu_urgent_qs, false); + } + if (rcu_pending()) + invoke_rcu_core(); + + trace_rcu_utilization(TPS("End scheduler-tick")); +} + +/* + * Scan the leaf rcu_node structures, processing dyntick state for any that + * have not yet encountered a quiescent state, using the function specified. + * Also initiate boosting for any threads blocked on the root rcu_node. + * + * The caller must have suppressed start of new grace periods. + */ +static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp)) +{ + int cpu; + unsigned long flags; + unsigned long mask; + struct rcu_node *rnp; + + rcu_for_each_leaf_node(rsp, rnp) { + cond_resched_tasks_rcu_qs(); + mask = 0; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + if (rnp->qsmask == 0) { + if (rcu_state_p == &rcu_sched_state || + rsp != rcu_state_p || + rcu_preempt_blocked_readers_cgp(rnp)) { + /* + * No point in scanning bits because they + * are all zero. But we might need to + * priority-boost blocked readers. + */ + rcu_initiate_boost(rnp, flags); + /* rcu_initiate_boost() releases rnp->lock */ + continue; + } + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + continue; + } + for_each_leaf_node_possible_cpu(rnp, cpu) { + unsigned long bit = leaf_node_cpu_bit(rnp, cpu); + if ((rnp->qsmask & bit) != 0) { + if (f(per_cpu_ptr(rsp->rda, cpu))) + mask |= bit; + } + } + if (mask != 0) { + /* Idle/offline CPUs, report (releases rnp->lock). */ + rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags); + } else { + /* Nothing to do here, so just drop the lock. */ + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + } +} + +/* + * Force quiescent states on reluctant CPUs, and also detect which + * CPUs are in dyntick-idle mode. + */ +static void force_quiescent_state(struct rcu_state *rsp) +{ + unsigned long flags; + bool ret; + struct rcu_node *rnp; + struct rcu_node *rnp_old = NULL; + + /* Funnel through hierarchy to reduce memory contention. */ + rnp = __this_cpu_read(rsp->rda->mynode); + for (; rnp != NULL; rnp = rnp->parent) { + ret = (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || + !raw_spin_trylock(&rnp->fqslock); + if (rnp_old != NULL) + raw_spin_unlock(&rnp_old->fqslock); + if (ret) + return; + rnp_old = rnp; + } + /* rnp_old == rcu_get_root(rsp), rnp == NULL. */ + + /* Reached the root of the rcu_node tree, acquire lock. */ + raw_spin_lock_irqsave_rcu_node(rnp_old, flags); + raw_spin_unlock(&rnp_old->fqslock); + if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { + raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); + return; /* Someone beat us to it. */ + } + WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS); + raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); + rcu_gp_kthread_wake(rsp); +} + +/* + * This function checks for grace-period requests that fail to motivate + * RCU to come out of its idle mode. + */ +static void +rcu_check_gp_start_stall(struct rcu_state *rsp, struct rcu_node *rnp, + struct rcu_data *rdp) +{ + const unsigned long gpssdelay = rcu_jiffies_till_stall_check() * HZ; + unsigned long flags; + unsigned long j; + struct rcu_node *rnp_root = rcu_get_root(rsp); + static atomic_t warned = ATOMIC_INIT(0); + + if (!IS_ENABLED(CONFIG_PROVE_RCU) || rcu_gp_in_progress(rsp) || + ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed)) + return; + j = jiffies; /* Expensive access, and in common case don't get here. */ + if (time_before(j, READ_ONCE(rsp->gp_req_activity) + gpssdelay) || + time_before(j, READ_ONCE(rsp->gp_activity) + gpssdelay) || + atomic_read(&warned)) + return; + + raw_spin_lock_irqsave_rcu_node(rnp, flags); + j = jiffies; + if (rcu_gp_in_progress(rsp) || + ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) || + time_before(j, READ_ONCE(rsp->gp_req_activity) + gpssdelay) || + time_before(j, READ_ONCE(rsp->gp_activity) + gpssdelay) || + atomic_read(&warned)) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + /* Hold onto the leaf lock to make others see warned==1. */ + + if (rnp_root != rnp) + raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */ + j = jiffies; + if (rcu_gp_in_progress(rsp) || + ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) || + time_before(j, rsp->gp_req_activity + gpssdelay) || + time_before(j, rsp->gp_activity + gpssdelay) || + atomic_xchg(&warned, 1)) { + raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */ + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + pr_alert("%s: g%ld->%ld gar:%lu ga:%lu f%#x gs:%d %s->state:%#lx\n", + __func__, (long)READ_ONCE(rsp->gp_seq), + (long)READ_ONCE(rnp_root->gp_seq_needed), + j - rsp->gp_req_activity, j - rsp->gp_activity, + rsp->gp_flags, rsp->gp_state, rsp->name, + rsp->gp_kthread ? rsp->gp_kthread->state : 0x1ffffL); + WARN_ON(1); + if (rnp_root != rnp) + raw_spin_unlock_rcu_node(rnp_root); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); +} + +/* + * This does the RCU core processing work for the specified rcu_state + * and rcu_data structures. This may be called only from the CPU to + * whom the rdp belongs. + */ +static void +__rcu_process_callbacks(struct rcu_state *rsp) +{ + unsigned long flags; + struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); + struct rcu_node *rnp = rdp->mynode; + + WARN_ON_ONCE(!rdp->beenonline); + + /* Update RCU state based on any recent quiescent states. */ + rcu_check_quiescent_state(rsp, rdp); + + /* No grace period and unregistered callbacks? */ + if (!rcu_gp_in_progress(rsp) && + rcu_segcblist_is_enabled(&rdp->cblist)) { + local_irq_save(flags); + if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) + rcu_accelerate_cbs_unlocked(rsp, rnp, rdp); + local_irq_restore(flags); + } + + rcu_check_gp_start_stall(rsp, rnp, rdp); + + /* If there are callbacks ready, invoke them. */ + if (rcu_segcblist_ready_cbs(&rdp->cblist)) + invoke_rcu_callbacks(rsp, rdp); + + /* Do any needed deferred wakeups of rcuo kthreads. */ + do_nocb_deferred_wakeup(rdp); +} + +/* + * Do RCU core processing for the current CPU. + */ +static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused) +{ + struct rcu_state *rsp; + + if (cpu_is_offline(smp_processor_id())) + return; + trace_rcu_utilization(TPS("Start RCU core")); + for_each_rcu_flavor(rsp) + __rcu_process_callbacks(rsp); + trace_rcu_utilization(TPS("End RCU core")); +} + +/* + * Schedule RCU callback invocation. If the specified type of RCU + * does not support RCU priority boosting, just do a direct call, + * otherwise wake up the per-CPU kernel kthread. Note that because we + * are running on the current CPU with softirqs disabled, the + * rcu_cpu_kthread_task cannot disappear out from under us. + */ +static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) +{ + if (unlikely(!READ_ONCE(rcu_scheduler_fully_active))) + return; + if (likely(!rsp->boost)) { + rcu_do_batch(rsp, rdp); + return; + } + invoke_rcu_callbacks_kthread(); +} + +static void invoke_rcu_core(void) +{ + if (cpu_online(smp_processor_id())) + raise_softirq(RCU_SOFTIRQ); +} + +/* + * Handle any core-RCU processing required by a call_rcu() invocation. + */ +static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, + struct rcu_head *head, unsigned long flags) +{ + /* + * If called from an extended quiescent state, invoke the RCU + * core in order to force a re-evaluation of RCU's idleness. + */ + if (!rcu_is_watching()) + invoke_rcu_core(); + + /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ + if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) + return; + + /* + * Force the grace period if too many callbacks or too long waiting. + * Enforce hysteresis, and don't invoke force_quiescent_state() + * if some other CPU has recently done so. Also, don't bother + * invoking force_quiescent_state() if the newly enqueued callback + * is the only one waiting for a grace period to complete. + */ + if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) > + rdp->qlen_last_fqs_check + qhimark)) { + + /* Are we ignoring a completed grace period? */ + note_gp_changes(rsp, rdp); + + /* Start a new grace period if one not already started. */ + if (!rcu_gp_in_progress(rsp)) { + rcu_accelerate_cbs_unlocked(rsp, rdp->mynode, rdp); + } else { + /* Give the grace period a kick. */ + rdp->blimit = LONG_MAX; + if (rsp->n_force_qs == rdp->n_force_qs_snap && + rcu_segcblist_first_pend_cb(&rdp->cblist) != head) + force_quiescent_state(rsp); + rdp->n_force_qs_snap = rsp->n_force_qs; + rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); + } + } +} + +/* + * RCU callback function to leak a callback. + */ +static void rcu_leak_callback(struct rcu_head *rhp) +{ +} + +/* + * Helper function for call_rcu() and friends. The cpu argument will + * normally be -1, indicating "currently running CPU". It may specify + * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier() + * is expected to specify a CPU. + */ +static void +__call_rcu(struct rcu_head *head, rcu_callback_t func, + struct rcu_state *rsp, int cpu, bool lazy) +{ + unsigned long flags; + struct rcu_data *rdp; + + /* Misaligned rcu_head! */ + WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1)); + + if (debug_rcu_head_queue(head)) { + /* + * Probable double call_rcu(), so leak the callback. + * Use rcu:rcu_callback trace event to find the previous + * time callback was passed to __call_rcu(). + */ + WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pF()!!!\n", + head, head->func); + WRITE_ONCE(head->func, rcu_leak_callback); + return; + } + head->func = func; + head->next = NULL; + local_irq_save(flags); + rdp = this_cpu_ptr(rsp->rda); + + /* Add the callback to our list. */ + if (unlikely(!rcu_segcblist_is_enabled(&rdp->cblist)) || cpu != -1) { + int offline; + + if (cpu != -1) + rdp = per_cpu_ptr(rsp->rda, cpu); + if (likely(rdp->mynode)) { + /* Post-boot, so this should be for a no-CBs CPU. */ + offline = !__call_rcu_nocb(rdp, head, lazy, flags); + WARN_ON_ONCE(offline); + /* Offline CPU, _call_rcu() illegal, leak callback. */ + local_irq_restore(flags); + return; + } + /* + * Very early boot, before rcu_init(). Initialize if needed + * and then drop through to queue the callback. + */ + BUG_ON(cpu != -1); + WARN_ON_ONCE(!rcu_is_watching()); + if (rcu_segcblist_empty(&rdp->cblist)) + rcu_segcblist_init(&rdp->cblist); + } + rcu_segcblist_enqueue(&rdp->cblist, head, lazy); + if (!lazy) + rcu_idle_count_callbacks_posted(); + + if (__is_kfree_rcu_offset((unsigned long)func)) + trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, + rcu_segcblist_n_lazy_cbs(&rdp->cblist), + rcu_segcblist_n_cbs(&rdp->cblist)); + else + trace_rcu_callback(rsp->name, head, + rcu_segcblist_n_lazy_cbs(&rdp->cblist), + rcu_segcblist_n_cbs(&rdp->cblist)); + + /* Go handle any RCU core processing required. */ + __call_rcu_core(rsp, rdp, head, flags); + local_irq_restore(flags); +} + +/** + * call_rcu_sched() - Queue an RCU for invocation after sched grace period. + * @head: structure to be used for queueing the RCU updates. + * @func: actual callback function to be invoked after the grace period + * + * The callback function will be invoked some time after a full grace + * period elapses, in other words after all currently executing RCU + * read-side critical sections have completed. call_rcu_sched() assumes + * that the read-side critical sections end on enabling of preemption + * or on voluntary preemption. + * RCU read-side critical sections are delimited by: + * + * - rcu_read_lock_sched() and rcu_read_unlock_sched(), OR + * - anything that disables preemption. + * + * These may be nested. + * + * See the description of call_rcu() for more detailed information on + * memory ordering guarantees. + */ +void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) +{ + __call_rcu(head, func, &rcu_sched_state, -1, 0); +} +EXPORT_SYMBOL_GPL(call_rcu_sched); + +/** + * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. + * @head: structure to be used for queueing the RCU updates. + * @func: actual callback function to be invoked after the grace period + * + * The callback function will be invoked some time after a full grace + * period elapses, in other words after all currently executing RCU + * read-side critical sections have completed. call_rcu_bh() assumes + * that the read-side critical sections end on completion of a softirq + * handler. This means that read-side critical sections in process + * context must not be interrupted by softirqs. This interface is to be + * used when most of the read-side critical sections are in softirq context. + * RCU read-side critical sections are delimited by: + * + * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context, OR + * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. + * + * These may be nested. + * + * See the description of call_rcu() for more detailed information on + * memory ordering guarantees. + */ +void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) +{ + __call_rcu(head, func, &rcu_bh_state, -1, 0); +} +EXPORT_SYMBOL_GPL(call_rcu_bh); + +/* + * Queue an RCU callback for lazy invocation after a grace period. + * This will likely be later named something like "call_rcu_lazy()", + * but this change will require some way of tagging the lazy RCU + * callbacks in the list of pending callbacks. Until then, this + * function may only be called from __kfree_rcu(). + */ +void kfree_call_rcu(struct rcu_head *head, + rcu_callback_t func) +{ + __call_rcu(head, func, rcu_state_p, -1, 1); +} +EXPORT_SYMBOL_GPL(kfree_call_rcu); + +/* + * Because a context switch is a grace period for RCU-sched and RCU-bh, + * any blocking grace-period wait automatically implies a grace period + * if there is only one CPU online at any point time during execution + * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to + * occasionally incorrectly indicate that there are multiple CPUs online + * when there was in fact only one the whole time, as this just adds + * some overhead: RCU still operates correctly. + */ +static int rcu_blocking_is_gp(void) +{ + int ret; + + might_sleep(); /* Check for RCU read-side critical section. */ + preempt_disable(); + ret = num_online_cpus() <= 1; + preempt_enable(); + return ret; +} + +/** + * synchronize_sched - wait until an rcu-sched grace period has elapsed. + * + * Control will return to the caller some time after a full rcu-sched + * grace period has elapsed, in other words after all currently executing + * rcu-sched read-side critical sections have completed. These read-side + * critical sections are delimited by rcu_read_lock_sched() and + * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), + * local_irq_disable(), and so on may be used in place of + * rcu_read_lock_sched(). + * + * This means that all preempt_disable code sequences, including NMI and + * non-threaded hardware-interrupt handlers, in progress on entry will + * have completed before this primitive returns. However, this does not + * guarantee that softirq handlers will have completed, since in some + * kernels, these handlers can run in process context, and can block. + * + * Note that this guarantee implies further memory-ordering guarantees. + * On systems with more than one CPU, when synchronize_sched() returns, + * each CPU is guaranteed to have executed a full memory barrier since the + * end of its last RCU-sched read-side critical section whose beginning + * preceded the call to synchronize_sched(). In addition, each CPU having + * an RCU read-side critical section that extends beyond the return from + * synchronize_sched() is guaranteed to have executed a full memory barrier + * after the beginning of synchronize_sched() and before the beginning of + * that RCU read-side critical section. Note that these guarantees include + * CPUs that are offline, idle, or executing in user mode, as well as CPUs + * that are executing in the kernel. + * + * Furthermore, if CPU A invoked synchronize_sched(), which returned + * to its caller on CPU B, then both CPU A and CPU B are guaranteed + * to have executed a full memory barrier during the execution of + * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but + * again only if the system has more than one CPU). + */ +void synchronize_sched(void) +{ + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_sched() in RCU-sched read-side critical section"); + if (rcu_blocking_is_gp()) + return; + if (rcu_gp_is_expedited()) + synchronize_sched_expedited(); + else + wait_rcu_gp(call_rcu_sched); +} +EXPORT_SYMBOL_GPL(synchronize_sched); + +/** + * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. + * + * Control will return to the caller some time after a full rcu_bh grace + * period has elapsed, in other words after all currently executing rcu_bh + * read-side critical sections have completed. RCU read-side critical + * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), + * and may be nested. + * + * See the description of synchronize_sched() for more detailed information + * on memory ordering guarantees. + */ +void synchronize_rcu_bh(void) +{ + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); + if (rcu_blocking_is_gp()) + return; + if (rcu_gp_is_expedited()) + synchronize_rcu_bh_expedited(); + else + wait_rcu_gp(call_rcu_bh); +} +EXPORT_SYMBOL_GPL(synchronize_rcu_bh); + +/** + * get_state_synchronize_rcu - Snapshot current RCU state + * + * Returns a cookie that is used by a later call to cond_synchronize_rcu() + * to determine whether or not a full grace period has elapsed in the + * meantime. + */ +unsigned long get_state_synchronize_rcu(void) +{ + /* + * Any prior manipulation of RCU-protected data must happen + * before the load from ->gp_seq. + */ + smp_mb(); /* ^^^ */ + return rcu_seq_snap(&rcu_state_p->gp_seq); +} +EXPORT_SYMBOL_GPL(get_state_synchronize_rcu); + +/** + * cond_synchronize_rcu - Conditionally wait for an RCU grace period + * + * @oldstate: return value from earlier call to get_state_synchronize_rcu() + * + * If a full RCU grace period has elapsed since the earlier call to + * get_state_synchronize_rcu(), just return. Otherwise, invoke + * synchronize_rcu() to wait for a full grace period. + * + * Yes, this function does not take counter wrap into account. But + * counter wrap is harmless. If the counter wraps, we have waited for + * more than 2 billion grace periods (and way more on a 64-bit system!), + * so waiting for one additional grace period should be just fine. + */ +void cond_synchronize_rcu(unsigned long oldstate) +{ + if (!rcu_seq_done(&rcu_state_p->gp_seq, oldstate)) + synchronize_rcu(); + else + smp_mb(); /* Ensure GP ends before subsequent accesses. */ +} +EXPORT_SYMBOL_GPL(cond_synchronize_rcu); + +/** + * get_state_synchronize_sched - Snapshot current RCU-sched state + * + * Returns a cookie that is used by a later call to cond_synchronize_sched() + * to determine whether or not a full grace period has elapsed in the + * meantime. + */ +unsigned long get_state_synchronize_sched(void) +{ + /* + * Any prior manipulation of RCU-protected data must happen + * before the load from ->gp_seq. + */ + smp_mb(); /* ^^^ */ + return rcu_seq_snap(&rcu_sched_state.gp_seq); +} +EXPORT_SYMBOL_GPL(get_state_synchronize_sched); + +/** + * cond_synchronize_sched - Conditionally wait for an RCU-sched grace period + * + * @oldstate: return value from earlier call to get_state_synchronize_sched() + * + * If a full RCU-sched grace period has elapsed since the earlier call to + * get_state_synchronize_sched(), just return. Otherwise, invoke + * synchronize_sched() to wait for a full grace period. + * + * Yes, this function does not take counter wrap into account. But + * counter wrap is harmless. If the counter wraps, we have waited for + * more than 2 billion grace periods (and way more on a 64-bit system!), + * so waiting for one additional grace period should be just fine. + */ +void cond_synchronize_sched(unsigned long oldstate) +{ + if (!rcu_seq_done(&rcu_sched_state.gp_seq, oldstate)) + synchronize_sched(); + else + smp_mb(); /* Ensure GP ends before subsequent accesses. */ +} +EXPORT_SYMBOL_GPL(cond_synchronize_sched); + +/* + * Check to see if there is any immediate RCU-related work to be done + * by the current CPU, for the specified type of RCU, returning 1 if so. + * The checks are in order of increasing expense: checks that can be + * carried out against CPU-local state are performed first. However, + * we must check for CPU stalls first, else we might not get a chance. + */ +static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) +{ + struct rcu_node *rnp = rdp->mynode; + + /* Check for CPU stalls, if enabled. */ + check_cpu_stall(rsp, rdp); + + /* Is this CPU a NO_HZ_FULL CPU that should ignore RCU? */ + if (rcu_nohz_full_cpu(rsp)) + return 0; + + /* Is the RCU core waiting for a quiescent state from this CPU? */ + if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm) + return 1; + + /* Does this CPU have callbacks ready to invoke? */ + if (rcu_segcblist_ready_cbs(&rdp->cblist)) + return 1; + + /* Has RCU gone idle with this CPU needing another grace period? */ + if (!rcu_gp_in_progress(rsp) && + rcu_segcblist_is_enabled(&rdp->cblist) && + !rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) + return 1; + + /* Have RCU grace period completed or started? */ + if (rcu_seq_current(&rnp->gp_seq) != rdp->gp_seq || + unlikely(READ_ONCE(rdp->gpwrap))) /* outside lock */ + return 1; + + /* Does this CPU need a deferred NOCB wakeup? */ + if (rcu_nocb_need_deferred_wakeup(rdp)) + return 1; + + /* nothing to do */ + return 0; +} + +/* + * Check to see if there is any immediate RCU-related work to be done + * by the current CPU, returning 1 if so. This function is part of the + * RCU implementation; it is -not- an exported member of the RCU API. + */ +static int rcu_pending(void) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + if (__rcu_pending(rsp, this_cpu_ptr(rsp->rda))) + return 1; + return 0; +} + +/* + * Return true if the specified CPU has any callback. If all_lazy is + * non-NULL, store an indication of whether all callbacks are lazy. + * (If there are no callbacks, all of them are deemed to be lazy.) + */ +static bool rcu_cpu_has_callbacks(bool *all_lazy) +{ + bool al = true; + bool hc = false; + struct rcu_data *rdp; + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) { + rdp = this_cpu_ptr(rsp->rda); + if (rcu_segcblist_empty(&rdp->cblist)) + continue; + hc = true; + if (rcu_segcblist_n_nonlazy_cbs(&rdp->cblist) || !all_lazy) { + al = false; + break; + } + } + if (all_lazy) + *all_lazy = al; + return hc; +} + +/* + * Helper function for _rcu_barrier() tracing. If tracing is disabled, + * the compiler is expected to optimize this away. + */ +static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s, + int cpu, unsigned long done) +{ + trace_rcu_barrier(rsp->name, s, cpu, + atomic_read(&rsp->barrier_cpu_count), done); +} + +/* + * RCU callback function for _rcu_barrier(). If we are last, wake + * up the task executing _rcu_barrier(). + */ +static void rcu_barrier_callback(struct rcu_head *rhp) +{ + struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); + struct rcu_state *rsp = rdp->rsp; + + if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { + _rcu_barrier_trace(rsp, TPS("LastCB"), -1, + rsp->barrier_sequence); + complete(&rsp->barrier_completion); + } else { + _rcu_barrier_trace(rsp, TPS("CB"), -1, rsp->barrier_sequence); + } +} + +/* + * Called with preemption disabled, and from cross-cpu IRQ context. + */ +static void rcu_barrier_func(void *type) +{ + struct rcu_state *rsp = type; + struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); + + _rcu_barrier_trace(rsp, TPS("IRQ"), -1, rsp->barrier_sequence); + rdp->barrier_head.func = rcu_barrier_callback; + debug_rcu_head_queue(&rdp->barrier_head); + if (rcu_segcblist_entrain(&rdp->cblist, &rdp->barrier_head, 0)) { + atomic_inc(&rsp->barrier_cpu_count); + } else { + debug_rcu_head_unqueue(&rdp->barrier_head); + _rcu_barrier_trace(rsp, TPS("IRQNQ"), -1, + rsp->barrier_sequence); + } +} + +/* + * Orchestrate the specified type of RCU barrier, waiting for all + * RCU callbacks of the specified type to complete. + */ +static void _rcu_barrier(struct rcu_state *rsp) +{ + int cpu; + struct rcu_data *rdp; + unsigned long s = rcu_seq_snap(&rsp->barrier_sequence); + + _rcu_barrier_trace(rsp, TPS("Begin"), -1, s); + + /* Take mutex to serialize concurrent rcu_barrier() requests. */ + mutex_lock(&rsp->barrier_mutex); + + /* Did someone else do our work for us? */ + if (rcu_seq_done(&rsp->barrier_sequence, s)) { + _rcu_barrier_trace(rsp, TPS("EarlyExit"), -1, + rsp->barrier_sequence); + smp_mb(); /* caller's subsequent code after above check. */ + mutex_unlock(&rsp->barrier_mutex); + return; + } + + /* Mark the start of the barrier operation. */ + rcu_seq_start(&rsp->barrier_sequence); + _rcu_barrier_trace(rsp, TPS("Inc1"), -1, rsp->barrier_sequence); + + /* + * Initialize the count to one rather than to zero in order to + * avoid a too-soon return to zero in case of a short grace period + * (or preemption of this task). Exclude CPU-hotplug operations + * to ensure that no offline CPU has callbacks queued. + */ + init_completion(&rsp->barrier_completion); + atomic_set(&rsp->barrier_cpu_count, 1); + get_online_cpus(); + + /* + * Force each CPU with callbacks to register a new callback. + * When that callback is invoked, we will know that all of the + * corresponding CPU's preceding callbacks have been invoked. + */ + for_each_possible_cpu(cpu) { + if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu)) + continue; + rdp = per_cpu_ptr(rsp->rda, cpu); + if (rcu_is_nocb_cpu(cpu)) { + if (!rcu_nocb_cpu_needs_barrier(rsp, cpu)) { + _rcu_barrier_trace(rsp, TPS("OfflineNoCB"), cpu, + rsp->barrier_sequence); + } else { + _rcu_barrier_trace(rsp, TPS("OnlineNoCB"), cpu, + rsp->barrier_sequence); + smp_mb__before_atomic(); + atomic_inc(&rsp->barrier_cpu_count); + __call_rcu(&rdp->barrier_head, + rcu_barrier_callback, rsp, cpu, 0); + } + } else if (rcu_segcblist_n_cbs(&rdp->cblist)) { + _rcu_barrier_trace(rsp, TPS("OnlineQ"), cpu, + rsp->barrier_sequence); + smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); + } else { + _rcu_barrier_trace(rsp, TPS("OnlineNQ"), cpu, + rsp->barrier_sequence); + } + } + put_online_cpus(); + + /* + * Now that we have an rcu_barrier_callback() callback on each + * CPU, and thus each counted, remove the initial count. + */ + if (atomic_dec_and_test(&rsp->barrier_cpu_count)) + complete(&rsp->barrier_completion); + + /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ + wait_for_completion(&rsp->barrier_completion); + + /* Mark the end of the barrier operation. */ + _rcu_barrier_trace(rsp, TPS("Inc2"), -1, rsp->barrier_sequence); + rcu_seq_end(&rsp->barrier_sequence); + + /* Other rcu_barrier() invocations can now safely proceed. */ + mutex_unlock(&rsp->barrier_mutex); +} + +/** + * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. + */ +void rcu_barrier_bh(void) +{ + _rcu_barrier(&rcu_bh_state); +} +EXPORT_SYMBOL_GPL(rcu_barrier_bh); + +/** + * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. + */ +void rcu_barrier_sched(void) +{ + _rcu_barrier(&rcu_sched_state); +} +EXPORT_SYMBOL_GPL(rcu_barrier_sched); + +/* + * Propagate ->qsinitmask bits up the rcu_node tree to account for the + * first CPU in a given leaf rcu_node structure coming online. The caller + * must hold the corresponding leaf rcu_node ->lock with interrrupts + * disabled. + */ +static void rcu_init_new_rnp(struct rcu_node *rnp_leaf) +{ + long mask; + long oldmask; + struct rcu_node *rnp = rnp_leaf; + + raw_lockdep_assert_held_rcu_node(rnp_leaf); + WARN_ON_ONCE(rnp->wait_blkd_tasks); + for (;;) { + mask = rnp->grpmask; + rnp = rnp->parent; + if (rnp == NULL) + return; + raw_spin_lock_rcu_node(rnp); /* Interrupts already disabled. */ + oldmask = rnp->qsmaskinit; + rnp->qsmaskinit |= mask; + raw_spin_unlock_rcu_node(rnp); /* Interrupts remain disabled. */ + if (oldmask) + return; + } +} + +/* + * Do boot-time initialization of a CPU's per-CPU RCU data. + */ +static void __init +rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) +{ + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + + /* Set up local state, ensuring consistent view of global state. */ + rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu); + rdp->dynticks = &per_cpu(rcu_dynticks, cpu); + WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != 1); + WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp->dynticks))); + rdp->rcu_ofl_gp_seq = rsp->gp_seq; + rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED; + rdp->rcu_onl_gp_seq = rsp->gp_seq; + rdp->rcu_onl_gp_flags = RCU_GP_CLEANED; + rdp->cpu = cpu; + rdp->rsp = rsp; + rcu_boot_init_nocb_percpu_data(rdp); +} + +/* + * Initialize a CPU's per-CPU RCU data. Note that only one online or + * offline event can be happening at a given time. Note also that we can + * accept some slop in the rsp->gp_seq access due to the fact that this + * CPU cannot possibly have any RCU callbacks in flight yet. + */ +static void +rcu_init_percpu_data(int cpu, struct rcu_state *rsp) +{ + unsigned long flags; + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_node *rnp = rcu_get_root(rsp); + + /* Set up local state, ensuring consistent view of global state. */ + raw_spin_lock_irqsave_rcu_node(rnp, flags); + rdp->qlen_last_fqs_check = 0; + rdp->n_force_qs_snap = rsp->n_force_qs; + rdp->blimit = blimit; + if (rcu_segcblist_empty(&rdp->cblist) && /* No early-boot CBs? */ + !init_nocb_callback_list(rdp)) + rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */ + rdp->dynticks->dynticks_nesting = 1; /* CPU not up, no tearing. */ + rcu_dynticks_eqs_online(); + raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ + + /* + * Add CPU to leaf rcu_node pending-online bitmask. Any needed + * propagation up the rcu_node tree will happen at the beginning + * of the next grace period. + */ + rnp = rdp->mynode; + raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ + rdp->beenonline = true; /* We have now been online. */ + rdp->gp_seq = rnp->gp_seq; + rdp->gp_seq_needed = rnp->gp_seq; + rdp->cpu_no_qs.b.norm = true; + rdp->rcu_qs_ctr_snap = per_cpu(rcu_dynticks.rcu_qs_ctr, cpu); + rdp->core_needs_qs = false; + rdp->rcu_iw_pending = false; + rdp->rcu_iw_gp_seq = rnp->gp_seq - 1; + trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("cpuonl")); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); +} + +/* + * Invoked early in the CPU-online process, when pretty much all + * services are available. The incoming CPU is not present. + */ +int rcutree_prepare_cpu(unsigned int cpu) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + rcu_init_percpu_data(cpu, rsp); + + rcu_prepare_kthreads(cpu); + rcu_spawn_all_nocb_kthreads(cpu); + + return 0; +} + +/* + * Update RCU priority boot kthread affinity for CPU-hotplug changes. + */ +static void rcutree_affinity_setting(unsigned int cpu, int outgoing) +{ + struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); + + rcu_boost_kthread_setaffinity(rdp->mynode, outgoing); +} + +/* + * Near the end of the CPU-online process. Pretty much all services + * enabled, and the CPU is now very much alive. + */ +int rcutree_online_cpu(unsigned int cpu) +{ + unsigned long flags; + struct rcu_data *rdp; + struct rcu_node *rnp; + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) { + rdp = per_cpu_ptr(rsp->rda, cpu); + rnp = rdp->mynode; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + rnp->ffmask |= rdp->grpmask; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + if (IS_ENABLED(CONFIG_TREE_SRCU)) + srcu_online_cpu(cpu); + if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) + return 0; /* Too early in boot for scheduler work. */ + sync_sched_exp_online_cleanup(cpu); + rcutree_affinity_setting(cpu, -1); + return 0; +} + +/* + * Near the beginning of the process. The CPU is still very much alive + * with pretty much all services enabled. + */ +int rcutree_offline_cpu(unsigned int cpu) +{ + unsigned long flags; + struct rcu_data *rdp; + struct rcu_node *rnp; + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) { + rdp = per_cpu_ptr(rsp->rda, cpu); + rnp = rdp->mynode; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + rnp->ffmask &= ~rdp->grpmask; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + + rcutree_affinity_setting(cpu, cpu); + if (IS_ENABLED(CONFIG_TREE_SRCU)) + srcu_offline_cpu(cpu); + return 0; +} + +/* + * Near the end of the offline process. We do only tracing here. + */ +int rcutree_dying_cpu(unsigned int cpu) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + rcu_cleanup_dying_cpu(rsp); + return 0; +} + +/* + * The outgoing CPU is gone and we are running elsewhere. + */ +int rcutree_dead_cpu(unsigned int cpu) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) { + rcu_cleanup_dead_cpu(cpu, rsp); + do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu)); + } + return 0; +} + +static DEFINE_PER_CPU(int, rcu_cpu_started); + +/* + * Mark the specified CPU as being online so that subsequent grace periods + * (both expedited and normal) will wait on it. Note that this means that + * incoming CPUs are not allowed to use RCU read-side critical sections + * until this function is called. Failing to observe this restriction + * will result in lockdep splats. + * + * Note that this function is special in that it is invoked directly + * from the incoming CPU rather than from the cpuhp_step mechanism. + * This is because this function must be invoked at a precise location. + */ +void rcu_cpu_starting(unsigned int cpu) +{ + unsigned long flags; + unsigned long mask; + int nbits; + unsigned long oldmask; + struct rcu_data *rdp; + struct rcu_node *rnp; + struct rcu_state *rsp; + + if (per_cpu(rcu_cpu_started, cpu)) + return; + + per_cpu(rcu_cpu_started, cpu) = 1; + + for_each_rcu_flavor(rsp) { + rdp = per_cpu_ptr(rsp->rda, cpu); + rnp = rdp->mynode; + mask = rdp->grpmask; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + rnp->qsmaskinitnext |= mask; + oldmask = rnp->expmaskinitnext; + rnp->expmaskinitnext |= mask; + oldmask ^= rnp->expmaskinitnext; + nbits = bitmap_weight(&oldmask, BITS_PER_LONG); + /* Allow lockless access for expedited grace periods. */ + smp_store_release(&rsp->ncpus, rsp->ncpus + nbits); /* ^^^ */ + rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */ + rdp->rcu_onl_gp_seq = READ_ONCE(rsp->gp_seq); + rdp->rcu_onl_gp_flags = READ_ONCE(rsp->gp_flags); + if (rnp->qsmask & mask) { /* RCU waiting on incoming CPU? */ + /* Report QS -after- changing ->qsmaskinitnext! */ + rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags); + } else { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + } + smp_mb(); /* Ensure RCU read-side usage follows above initialization. */ +} + +#ifdef CONFIG_HOTPLUG_CPU +/* + * The CPU is exiting the idle loop into the arch_cpu_idle_dead() + * function. We now remove it from the rcu_node tree's ->qsmaskinitnext + * bit masks. + */ +static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp) +{ + unsigned long flags; + unsigned long mask; + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ + + /* Remove outgoing CPU from mask in the leaf rcu_node structure. */ + mask = rdp->grpmask; + spin_lock(&rsp->ofl_lock); + raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */ + rdp->rcu_ofl_gp_seq = READ_ONCE(rsp->gp_seq); + rdp->rcu_ofl_gp_flags = READ_ONCE(rsp->gp_flags); + if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */ + /* Report quiescent state -before- changing ->qsmaskinitnext! */ + rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags); + raw_spin_lock_irqsave_rcu_node(rnp, flags); + } + rnp->qsmaskinitnext &= ~mask; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + spin_unlock(&rsp->ofl_lock); +} + +/* + * The outgoing function has no further need of RCU, so remove it from + * the list of CPUs that RCU must track. + * + * Note that this function is special in that it is invoked directly + * from the outgoing CPU rather than from the cpuhp_step mechanism. + * This is because this function must be invoked at a precise location. + */ +void rcu_report_dead(unsigned int cpu) +{ + struct rcu_state *rsp; + + /* QS for any half-done expedited RCU-sched GP. */ + preempt_disable(); + rcu_report_exp_rdp(&rcu_sched_state, + this_cpu_ptr(rcu_sched_state.rda), true); + preempt_enable(); + for_each_rcu_flavor(rsp) + rcu_cleanup_dying_idle_cpu(cpu, rsp); + + per_cpu(rcu_cpu_started, cpu) = 0; +} + +/* Migrate the dead CPU's callbacks to the current CPU. */ +static void rcu_migrate_callbacks(int cpu, struct rcu_state *rsp) +{ + unsigned long flags; + struct rcu_data *my_rdp; + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); + bool needwake; + + if (rcu_is_nocb_cpu(cpu) || rcu_segcblist_empty(&rdp->cblist)) + return; /* No callbacks to migrate. */ + + local_irq_save(flags); + my_rdp = this_cpu_ptr(rsp->rda); + if (rcu_nocb_adopt_orphan_cbs(my_rdp, rdp, flags)) { + local_irq_restore(flags); + return; + } + raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */ + /* Leverage recent GPs and set GP for new callbacks. */ + needwake = rcu_advance_cbs(rsp, rnp_root, rdp) || + rcu_advance_cbs(rsp, rnp_root, my_rdp); + rcu_segcblist_merge(&my_rdp->cblist, &rdp->cblist); + WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) != + !rcu_segcblist_n_cbs(&my_rdp->cblist)); + raw_spin_unlock_irqrestore_rcu_node(rnp_root, flags); + if (needwake) + rcu_gp_kthread_wake(rsp); + WARN_ONCE(rcu_segcblist_n_cbs(&rdp->cblist) != 0 || + !rcu_segcblist_empty(&rdp->cblist), + "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, 1stCB=%p\n", + cpu, rcu_segcblist_n_cbs(&rdp->cblist), + rcu_segcblist_first_cb(&rdp->cblist)); +} + +/* + * The outgoing CPU has just passed through the dying-idle state, + * and we are being invoked from the CPU that was IPIed to continue the + * offline operation. We need to migrate the outgoing CPU's callbacks. + */ +void rcutree_migrate_callbacks(int cpu) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + rcu_migrate_callbacks(cpu, rsp); +} +#endif + +/* + * On non-huge systems, use expedited RCU grace periods to make suspend + * and hibernation run faster. + */ +static int rcu_pm_notify(struct notifier_block *self, + unsigned long action, void *hcpu) +{ + switch (action) { + case PM_HIBERNATION_PREPARE: + case PM_SUSPEND_PREPARE: + if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ + rcu_expedite_gp(); + break; + case PM_POST_HIBERNATION: + case PM_POST_SUSPEND: + if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ + rcu_unexpedite_gp(); + break; + default: + break; + } + return NOTIFY_OK; +} + +/* + * Spawn the kthreads that handle each RCU flavor's grace periods. + */ +static int __init rcu_spawn_gp_kthread(void) +{ + unsigned long flags; + int kthread_prio_in = kthread_prio; + struct rcu_node *rnp; + struct rcu_state *rsp; + struct sched_param sp; + struct task_struct *t; + + /* Force priority into range. */ + if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 2 + && IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)) + kthread_prio = 2; + else if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1) + kthread_prio = 1; + else if (kthread_prio < 0) + kthread_prio = 0; + else if (kthread_prio > 99) + kthread_prio = 99; + + if (kthread_prio != kthread_prio_in) + pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n", + kthread_prio, kthread_prio_in); + + rcu_scheduler_fully_active = 1; + for_each_rcu_flavor(rsp) { + t = kthread_create(rcu_gp_kthread, rsp, "%s", rsp->name); + BUG_ON(IS_ERR(t)); + rnp = rcu_get_root(rsp); + raw_spin_lock_irqsave_rcu_node(rnp, flags); + rsp->gp_kthread = t; + if (kthread_prio) { + sp.sched_priority = kthread_prio; + sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); + } + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + wake_up_process(t); + } + rcu_spawn_nocb_kthreads(); + rcu_spawn_boost_kthreads(); + return 0; +} +early_initcall(rcu_spawn_gp_kthread); + +/* + * This function is invoked towards the end of the scheduler's + * initialization process. Before this is called, the idle task might + * contain synchronous grace-period primitives (during which time, this idle + * task is booting the system, and such primitives are no-ops). After this + * function is called, any synchronous grace-period primitives are run as + * expedited, with the requesting task driving the grace period forward. + * A later core_initcall() rcu_set_runtime_mode() will switch to full + * runtime RCU functionality. + */ +void rcu_scheduler_starting(void) +{ + WARN_ON(num_online_cpus() != 1); + WARN_ON(nr_context_switches() > 0); + rcu_test_sync_prims(); + rcu_scheduler_active = RCU_SCHEDULER_INIT; + rcu_test_sync_prims(); +} + +/* + * Helper function for rcu_init() that initializes one rcu_state structure. + */ +static void __init rcu_init_one(struct rcu_state *rsp) +{ + static const char * const buf[] = RCU_NODE_NAME_INIT; + static const char * const fqs[] = RCU_FQS_NAME_INIT; + static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; + static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; + + int levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */ + int cpustride = 1; + int i; + int j; + struct rcu_node *rnp; + + BUILD_BUG_ON(RCU_NUM_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ + + /* Silence gcc 4.8 false positive about array index out of range. */ + if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS) + panic("rcu_init_one: rcu_num_lvls out of range"); + + /* Initialize the level-tracking arrays. */ + + for (i = 1; i < rcu_num_lvls; i++) + rsp->level[i] = rsp->level[i - 1] + num_rcu_lvl[i - 1]; + rcu_init_levelspread(levelspread, num_rcu_lvl); + + /* Initialize the elements themselves, starting from the leaves. */ + + for (i = rcu_num_lvls - 1; i >= 0; i--) { + cpustride *= levelspread[i]; + rnp = rsp->level[i]; + for (j = 0; j < num_rcu_lvl[i]; j++, rnp++) { + raw_spin_lock_init(&ACCESS_PRIVATE(rnp, lock)); + lockdep_set_class_and_name(&ACCESS_PRIVATE(rnp, lock), + &rcu_node_class[i], buf[i]); + raw_spin_lock_init(&rnp->fqslock); + lockdep_set_class_and_name(&rnp->fqslock, + &rcu_fqs_class[i], fqs[i]); + rnp->gp_seq = rsp->gp_seq; + rnp->gp_seq_needed = rsp->gp_seq; + rnp->completedqs = rsp->gp_seq; + rnp->qsmask = 0; + rnp->qsmaskinit = 0; + rnp->grplo = j * cpustride; + rnp->grphi = (j + 1) * cpustride - 1; + if (rnp->grphi >= nr_cpu_ids) + rnp->grphi = nr_cpu_ids - 1; + if (i == 0) { + rnp->grpnum = 0; + rnp->grpmask = 0; + rnp->parent = NULL; + } else { + rnp->grpnum = j % levelspread[i - 1]; + rnp->grpmask = 1UL << rnp->grpnum; + rnp->parent = rsp->level[i - 1] + + j / levelspread[i - 1]; + } + rnp->level = i; + INIT_LIST_HEAD(&rnp->blkd_tasks); + rcu_init_one_nocb(rnp); + init_waitqueue_head(&rnp->exp_wq[0]); + init_waitqueue_head(&rnp->exp_wq[1]); + init_waitqueue_head(&rnp->exp_wq[2]); + init_waitqueue_head(&rnp->exp_wq[3]); + spin_lock_init(&rnp->exp_lock); + } + } + + init_swait_queue_head(&rsp->gp_wq); + init_swait_queue_head(&rsp->expedited_wq); + rnp = rcu_first_leaf_node(rsp); + for_each_possible_cpu(i) { + while (i > rnp->grphi) + rnp++; + per_cpu_ptr(rsp->rda, i)->mynode = rnp; + rcu_boot_init_percpu_data(i, rsp); + } + list_add(&rsp->flavors, &rcu_struct_flavors); +} + +/* + * Compute the rcu_node tree geometry from kernel parameters. This cannot + * replace the definitions in tree.h because those are needed to size + * the ->node array in the rcu_state structure. + */ +static void __init rcu_init_geometry(void) +{ + ulong d; + int i; + int rcu_capacity[RCU_NUM_LVLS]; + + /* + * Initialize any unspecified boot parameters. + * The default values of jiffies_till_first_fqs and + * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS + * value, which is a function of HZ, then adding one for each + * RCU_JIFFIES_FQS_DIV CPUs that might be on the system. + */ + d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; + if (jiffies_till_first_fqs == ULONG_MAX) + jiffies_till_first_fqs = d; + if (jiffies_till_next_fqs == ULONG_MAX) + jiffies_till_next_fqs = d; + + /* If the compile-time values are accurate, just leave. */ + if (rcu_fanout_leaf == RCU_FANOUT_LEAF && + nr_cpu_ids == NR_CPUS) + return; + pr_info("Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n", + rcu_fanout_leaf, nr_cpu_ids); + + /* + * The boot-time rcu_fanout_leaf parameter must be at least two + * and cannot exceed the number of bits in the rcu_node masks. + * Complain and fall back to the compile-time values if this + * limit is exceeded. + */ + if (rcu_fanout_leaf < 2 || + rcu_fanout_leaf > sizeof(unsigned long) * 8) { + rcu_fanout_leaf = RCU_FANOUT_LEAF; + WARN_ON(1); + return; + } + + /* + * Compute number of nodes that can be handled an rcu_node tree + * with the given number of levels. + */ + rcu_capacity[0] = rcu_fanout_leaf; + for (i = 1; i < RCU_NUM_LVLS; i++) + rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT; + + /* + * The tree must be able to accommodate the configured number of CPUs. + * If this limit is exceeded, fall back to the compile-time values. + */ + if (nr_cpu_ids > rcu_capacity[RCU_NUM_LVLS - 1]) { + rcu_fanout_leaf = RCU_FANOUT_LEAF; + WARN_ON(1); + return; + } + + /* Calculate the number of levels in the tree. */ + for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) { + } + rcu_num_lvls = i + 1; + + /* Calculate the number of rcu_nodes at each level of the tree. */ + for (i = 0; i < rcu_num_lvls; i++) { + int cap = rcu_capacity[(rcu_num_lvls - 1) - i]; + num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap); + } + + /* Calculate the total number of rcu_node structures. */ + rcu_num_nodes = 0; + for (i = 0; i < rcu_num_lvls; i++) + rcu_num_nodes += num_rcu_lvl[i]; +} + +/* + * Dump out the structure of the rcu_node combining tree associated + * with the rcu_state structure referenced by rsp. + */ +static void __init rcu_dump_rcu_node_tree(struct rcu_state *rsp) +{ + int level = 0; + struct rcu_node *rnp; + + pr_info("rcu_node tree layout dump\n"); + pr_info(" "); + rcu_for_each_node_breadth_first(rsp, rnp) { + if (rnp->level != level) { + pr_cont("\n"); + pr_info(" "); + level = rnp->level; + } + pr_cont("%d:%d ^%d ", rnp->grplo, rnp->grphi, rnp->grpnum); + } + pr_cont("\n"); +} + +struct workqueue_struct *rcu_gp_wq; +struct workqueue_struct *rcu_par_gp_wq; + +void __init rcu_init(void) +{ + int cpu; + + rcu_early_boot_tests(); + + rcu_bootup_announce(); + rcu_init_geometry(); + rcu_init_one(&rcu_bh_state); + rcu_init_one(&rcu_sched_state); + if (dump_tree) + rcu_dump_rcu_node_tree(&rcu_sched_state); + __rcu_init_preempt(); + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); + + /* + * We don't need protection against CPU-hotplug here because + * this is called early in boot, before either interrupts + * or the scheduler are operational. + */ + pm_notifier(rcu_pm_notify, 0); + for_each_online_cpu(cpu) { + rcutree_prepare_cpu(cpu); + rcu_cpu_starting(cpu); + rcutree_online_cpu(cpu); + } + + /* Create workqueue for expedited GPs and for Tree SRCU. */ + rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0); + WARN_ON(!rcu_gp_wq); + rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0); + WARN_ON(!rcu_par_gp_wq); +} + +#include "tree_exp.h" +#include "tree_plugin.h" diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h new file mode 100644 index 000000000..4e74df768 --- /dev/null +++ b/kernel/rcu/tree.h @@ -0,0 +1,500 @@ +/* + * Read-Copy Update mechanism for mutual exclusion (tree-based version) + * Internal non-public definitions. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2008 + * + * Author: Ingo Molnar <mingo@elte.hu> + * Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + +#include <linux/cache.h> +#include <linux/spinlock.h> +#include <linux/rtmutex.h> +#include <linux/threads.h> +#include <linux/cpumask.h> +#include <linux/seqlock.h> +#include <linux/swait.h> +#include <linux/stop_machine.h> +#include <linux/rcu_node_tree.h> + +#include "rcu_segcblist.h" + +/* + * Dynticks per-CPU state. + */ +struct rcu_dynticks { + long dynticks_nesting; /* Track process nesting level. */ + long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */ + atomic_t dynticks; /* Even value for idle, else odd. */ + bool rcu_need_heavy_qs; /* GP old, need heavy quiescent state. */ + unsigned long rcu_qs_ctr; /* Light universal quiescent state ctr. */ + bool rcu_urgent_qs; /* GP old need light quiescent state. */ +#ifdef CONFIG_RCU_FAST_NO_HZ + bool all_lazy; /* Are all CPU's CBs lazy? */ + unsigned long nonlazy_posted; + /* # times non-lazy CBs posted to CPU. */ + unsigned long nonlazy_posted_snap; + /* idle-period nonlazy_posted snapshot. */ + unsigned long last_accelerate; + /* Last jiffy CBs were accelerated. */ + unsigned long last_advance_all; + /* Last jiffy CBs were all advanced. */ + int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */ +#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ +}; + +/* Communicate arguments to a workqueue handler. */ +struct rcu_exp_work { + smp_call_func_t rew_func; + struct rcu_state *rew_rsp; + unsigned long rew_s; + struct work_struct rew_work; +}; + +/* RCU's kthread states for tracing. */ +#define RCU_KTHREAD_STOPPED 0 +#define RCU_KTHREAD_RUNNING 1 +#define RCU_KTHREAD_WAITING 2 +#define RCU_KTHREAD_OFFCPU 3 +#define RCU_KTHREAD_YIELDING 4 +#define RCU_KTHREAD_MAX 4 + +/* + * Definition for node within the RCU grace-period-detection hierarchy. + */ +struct rcu_node { + raw_spinlock_t __private lock; /* Root rcu_node's lock protects */ + /* some rcu_state fields as well as */ + /* following. */ + unsigned long gp_seq; /* Track rsp->rcu_gp_seq. */ + unsigned long gp_seq_needed; /* Track rsp->rcu_gp_seq_needed. */ + unsigned long completedqs; /* All QSes done for this node. */ + unsigned long qsmask; /* CPUs or groups that need to switch in */ + /* order for current grace period to proceed.*/ + /* In leaf rcu_node, each bit corresponds to */ + /* an rcu_data structure, otherwise, each */ + /* bit corresponds to a child rcu_node */ + /* structure. */ + unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */ + unsigned long qsmaskinit; + /* Per-GP initial value for qsmask. */ + /* Initialized from ->qsmaskinitnext at the */ + /* beginning of each grace period. */ + unsigned long qsmaskinitnext; + /* Online CPUs for next grace period. */ + unsigned long expmask; /* CPUs or groups that need to check in */ + /* to allow the current expedited GP */ + /* to complete. */ + unsigned long expmaskinit; + /* Per-GP initial values for expmask. */ + /* Initialized from ->expmaskinitnext at the */ + /* beginning of each expedited GP. */ + unsigned long expmaskinitnext; + /* Online CPUs for next expedited GP. */ + /* Any CPU that has ever been online will */ + /* have its bit set. */ + unsigned long ffmask; /* Fully functional CPUs. */ + unsigned long grpmask; /* Mask to apply to parent qsmask. */ + /* Only one bit will be set in this mask. */ + int grplo; /* lowest-numbered CPU or group here. */ + int grphi; /* highest-numbered CPU or group here. */ + u8 grpnum; /* CPU/group number for next level up. */ + u8 level; /* root is at level 0. */ + bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */ + /* exit RCU read-side critical sections */ + /* before propagating offline up the */ + /* rcu_node tree? */ + struct rcu_node *parent; + struct list_head blkd_tasks; + /* Tasks blocked in RCU read-side critical */ + /* section. Tasks are placed at the head */ + /* of this list and age towards the tail. */ + struct list_head *gp_tasks; + /* Pointer to the first task blocking the */ + /* current grace period, or NULL if there */ + /* is no such task. */ + struct list_head *exp_tasks; + /* Pointer to the first task blocking the */ + /* current expedited grace period, or NULL */ + /* if there is no such task. If there */ + /* is no current expedited grace period, */ + /* then there can cannot be any such task. */ + struct list_head *boost_tasks; + /* Pointer to first task that needs to be */ + /* priority boosted, or NULL if no priority */ + /* boosting is needed for this rcu_node */ + /* structure. If there are no tasks */ + /* queued on this rcu_node structure that */ + /* are blocking the current grace period, */ + /* there can be no such task. */ + struct rt_mutex boost_mtx; + /* Used only for the priority-boosting */ + /* side effect, not as a lock. */ + unsigned long boost_time; + /* When to start boosting (jiffies). */ + struct task_struct *boost_kthread_task; + /* kthread that takes care of priority */ + /* boosting for this rcu_node structure. */ + unsigned int boost_kthread_status; + /* State of boost_kthread_task for tracing. */ +#ifdef CONFIG_RCU_NOCB_CPU + struct swait_queue_head nocb_gp_wq[2]; + /* Place for rcu_nocb_kthread() to wait GP. */ +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ + raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp; + + spinlock_t exp_lock ____cacheline_internodealigned_in_smp; + unsigned long exp_seq_rq; + wait_queue_head_t exp_wq[4]; + struct rcu_exp_work rew; + bool exp_need_flush; /* Need to flush workitem? */ +} ____cacheline_internodealigned_in_smp; + +/* + * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and + * are indexed relative to this interval rather than the global CPU ID space. + * This generates the bit for a CPU in node-local masks. + */ +#define leaf_node_cpu_bit(rnp, cpu) (1UL << ((cpu) - (rnp)->grplo)) + +/* + * Union to allow "aggregate OR" operation on the need for a quiescent + * state by the normal and expedited grace periods. + */ +union rcu_noqs { + struct { + u8 norm; + u8 exp; + } b; /* Bits. */ + u16 s; /* Set of bits, aggregate OR here. */ +}; + +/* Per-CPU data for read-copy update. */ +struct rcu_data { + /* 1) quiescent-state and grace-period handling : */ + unsigned long gp_seq; /* Track rsp->rcu_gp_seq counter. */ + unsigned long gp_seq_needed; /* Track rsp->rcu_gp_seq_needed ctr. */ + unsigned long rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */ + /* for rcu_all_qs() invocations. */ + union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */ + bool core_needs_qs; /* Core waits for quiesc state. */ + bool beenonline; /* CPU online at least once. */ + bool gpwrap; /* Possible ->gp_seq wrap. */ + struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ + unsigned long grpmask; /* Mask to apply to leaf qsmask. */ + unsigned long ticks_this_gp; /* The number of scheduling-clock */ + /* ticks this CPU has handled */ + /* during and after the last grace */ + /* period it is aware of. */ + + /* 2) batch handling */ + struct rcu_segcblist cblist; /* Segmented callback list, with */ + /* different callbacks waiting for */ + /* different grace periods. */ + long qlen_last_fqs_check; + /* qlen at last check for QS forcing */ + unsigned long n_force_qs_snap; + /* did other CPU force QS recently? */ + long blimit; /* Upper limit on a processed batch */ + + /* 3) dynticks interface. */ + struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ + int dynticks_snap; /* Per-GP tracking for dynticks. */ + + /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ + unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ + unsigned long cond_resched_completed; + /* Grace period that needs help */ + /* from cond_resched(). */ + + /* 5) _rcu_barrier(), OOM callbacks, and expediting. */ + struct rcu_head barrier_head; +#ifdef CONFIG_RCU_FAST_NO_HZ + struct rcu_head oom_head; +#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ + int exp_dynticks_snap; /* Double-check need for IPI. */ + + /* 6) Callback offloading. */ +#ifdef CONFIG_RCU_NOCB_CPU + struct rcu_head *nocb_head; /* CBs waiting for kthread. */ + struct rcu_head **nocb_tail; + atomic_long_t nocb_q_count; /* # CBs waiting for nocb */ + atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */ + struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */ + struct rcu_head **nocb_follower_tail; + struct swait_queue_head nocb_wq; /* For nocb kthreads to sleep on. */ + struct task_struct *nocb_kthread; + raw_spinlock_t nocb_lock; /* Guard following pair of fields. */ + int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ + struct timer_list nocb_timer; /* Enforce finite deferral. */ + + /* The following fields are used by the leader, hence own cacheline. */ + struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp; + /* CBs waiting for GP. */ + struct rcu_head **nocb_gp_tail; + bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */ + struct rcu_data *nocb_next_follower; + /* Next follower in wakeup chain. */ + + /* The following fields are used by the follower, hence new cachline. */ + struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp; + /* Leader CPU takes GP-end wakeups. */ +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ + + /* 7) Diagnostic data, including RCU CPU stall warnings. */ + unsigned int softirq_snap; /* Snapshot of softirq activity. */ + /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */ + struct irq_work rcu_iw; /* Check for non-irq activity. */ + bool rcu_iw_pending; /* Is ->rcu_iw pending? */ + unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */ + unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */ + short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */ + unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */ + short rcu_onl_gp_flags; /* ->gp_flags at last online. */ + + int cpu; + struct rcu_state *rsp; +}; + +/* Values for nocb_defer_wakeup field in struct rcu_data. */ +#define RCU_NOCB_WAKE_NOT 0 +#define RCU_NOCB_WAKE 1 +#define RCU_NOCB_WAKE_FORCE 2 + +#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) + /* For jiffies_till_first_fqs and */ + /* and jiffies_till_next_fqs. */ + +#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */ + /* delay between bouts of */ + /* quiescent-state forcing. */ + +#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */ + /* at least one scheduling clock */ + /* irq before ratting on them. */ + +#define rcu_wait(cond) \ +do { \ + for (;;) { \ + set_current_state(TASK_INTERRUPTIBLE); \ + if (cond) \ + break; \ + schedule(); \ + } \ + __set_current_state(TASK_RUNNING); \ +} while (0) + +/* + * RCU global state, including node hierarchy. This hierarchy is + * represented in "heap" form in a dense array. The root (first level) + * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second + * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), + * and the third level in ->node[m+1] and following (->node[m+1] referenced + * by ->level[2]). The number of levels is determined by the number of + * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" + * consisting of a single rcu_node. + */ +struct rcu_state { + struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ + struct rcu_node *level[RCU_NUM_LVLS + 1]; + /* Hierarchy levels (+1 to */ + /* shut bogus gcc warning) */ + struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */ + call_rcu_func_t call; /* call_rcu() flavor. */ + int ncpus; /* # CPUs seen so far. */ + + /* The following fields are guarded by the root rcu_node's lock. */ + + u8 boost ____cacheline_internodealigned_in_smp; + /* Subject to priority boost. */ + unsigned long gp_seq; /* Grace-period sequence #. */ + struct task_struct *gp_kthread; /* Task for grace periods. */ + struct swait_queue_head gp_wq; /* Where GP task waits. */ + short gp_flags; /* Commands for GP task. */ + short gp_state; /* GP kthread sleep state. */ + + /* End of fields guarded by root rcu_node's lock. */ + + struct mutex barrier_mutex; /* Guards barrier fields. */ + atomic_t barrier_cpu_count; /* # CPUs waiting on. */ + struct completion barrier_completion; /* Wake at barrier end. */ + unsigned long barrier_sequence; /* ++ at start and end of */ + /* _rcu_barrier(). */ + /* End of fields guarded by barrier_mutex. */ + + struct mutex exp_mutex; /* Serialize expedited GP. */ + struct mutex exp_wake_mutex; /* Serialize wakeup. */ + unsigned long expedited_sequence; /* Take a ticket. */ + atomic_t expedited_need_qs; /* # CPUs left to check in. */ + struct swait_queue_head expedited_wq; /* Wait for check-ins. */ + int ncpus_snap; /* # CPUs seen last time. */ + + unsigned long jiffies_force_qs; /* Time at which to invoke */ + /* force_quiescent_state(). */ + unsigned long jiffies_kick_kthreads; /* Time at which to kick */ + /* kthreads, if configured. */ + unsigned long n_force_qs; /* Number of calls to */ + /* force_quiescent_state(). */ + unsigned long gp_start; /* Time at which GP started, */ + /* but in jiffies. */ + unsigned long gp_activity; /* Time of last GP kthread */ + /* activity in jiffies. */ + unsigned long gp_req_activity; /* Time of last GP request */ + /* in jiffies. */ + unsigned long jiffies_stall; /* Time at which to check */ + /* for CPU stalls. */ + unsigned long jiffies_resched; /* Time at which to resched */ + /* a reluctant CPU. */ + unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */ + /* GP start. */ + unsigned long gp_max; /* Maximum GP duration in */ + /* jiffies. */ + const char *name; /* Name of structure. */ + char abbr; /* Abbreviated name. */ + struct list_head flavors; /* List of RCU flavors. */ + + spinlock_t ofl_lock ____cacheline_internodealigned_in_smp; + /* Synchronize offline with */ + /* GP pre-initialization. */ +}; + +/* Values for rcu_state structure's gp_flags field. */ +#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */ +#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */ + +/* Values for rcu_state structure's gp_state field. */ +#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */ +#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */ +#define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */ +#define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */ +#define RCU_GP_INIT 4 /* Grace-period initialization. */ +#define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */ +#define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */ +#define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */ +#define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */ + +#ifndef RCU_TREE_NONCORE +static const char * const gp_state_names[] = { + "RCU_GP_IDLE", + "RCU_GP_WAIT_GPS", + "RCU_GP_DONE_GPS", + "RCU_GP_ONOFF", + "RCU_GP_INIT", + "RCU_GP_WAIT_FQS", + "RCU_GP_DOING_FQS", + "RCU_GP_CLEANUP", + "RCU_GP_CLEANED", +}; +#endif /* #ifndef RCU_TREE_NONCORE */ + +extern struct list_head rcu_struct_flavors; + +/* Sequence through rcu_state structures for each RCU flavor. */ +#define for_each_rcu_flavor(rsp) \ + list_for_each_entry((rsp), &rcu_struct_flavors, flavors) + +/* + * RCU implementation internal declarations: + */ +extern struct rcu_state rcu_sched_state; + +extern struct rcu_state rcu_bh_state; + +#ifdef CONFIG_PREEMPT_RCU +extern struct rcu_state rcu_preempt_state; +#endif /* #ifdef CONFIG_PREEMPT_RCU */ + +int rcu_dynticks_snap(struct rcu_dynticks *rdtp); + +#ifdef CONFIG_RCU_BOOST +DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status); +DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu); +DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); +DECLARE_PER_CPU(char, rcu_cpu_has_work); +#endif /* #ifdef CONFIG_RCU_BOOST */ + +#ifndef RCU_TREE_NONCORE + +/* Forward declarations for rcutree_plugin.h */ +static void rcu_bootup_announce(void); +static void rcu_preempt_note_context_switch(bool preempt); +static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); +#ifdef CONFIG_HOTPLUG_CPU +static bool rcu_preempt_has_tasks(struct rcu_node *rnp); +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ +static void rcu_print_detail_task_stall(struct rcu_state *rsp); +static int rcu_print_task_stall(struct rcu_node *rnp); +static int rcu_print_task_exp_stall(struct rcu_node *rnp); +static void rcu_preempt_check_blocked_tasks(struct rcu_state *rsp, + struct rcu_node *rnp); +static void rcu_preempt_check_callbacks(void); +void call_rcu(struct rcu_head *head, rcu_callback_t func); +static void __init __rcu_init_preempt(void); +static void dump_blkd_tasks(struct rcu_state *rsp, struct rcu_node *rnp, + int ncheck); +static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); +static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); +static void invoke_rcu_callbacks_kthread(void); +static bool rcu_is_callbacks_kthread(void); +#ifdef CONFIG_RCU_BOOST +static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, + struct rcu_node *rnp); +#endif /* #ifdef CONFIG_RCU_BOOST */ +static void __init rcu_spawn_boost_kthreads(void); +static void rcu_prepare_kthreads(int cpu); +static void rcu_cleanup_after_idle(void); +static void rcu_prepare_for_idle(void); +static void rcu_idle_count_callbacks_posted(void); +static bool rcu_preempt_has_tasks(struct rcu_node *rnp); +static void print_cpu_stall_info_begin(void); +static void print_cpu_stall_info(struct rcu_state *rsp, int cpu); +static void print_cpu_stall_info_end(void); +static void zero_cpu_stall_ticks(struct rcu_data *rdp); +static void increment_cpu_stall_ticks(void); +static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu); +static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp); +static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq); +static void rcu_init_one_nocb(struct rcu_node *rnp); +static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, + bool lazy, unsigned long flags); +static bool rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp, + struct rcu_data *rdp, + unsigned long flags); +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); +static void do_nocb_deferred_wakeup(struct rcu_data *rdp); +static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); +static void rcu_spawn_all_nocb_kthreads(int cpu); +static void __init rcu_spawn_nocb_kthreads(void); +#ifdef CONFIG_RCU_NOCB_CPU +static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp); +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ +static bool init_nocb_callback_list(struct rcu_data *rdp); +static void rcu_bind_gp_kthread(void); +static bool rcu_nohz_full_cpu(struct rcu_state *rsp); +static void rcu_dynticks_task_enter(void); +static void rcu_dynticks_task_exit(void); + +#ifdef CONFIG_SRCU +void srcu_online_cpu(unsigned int cpu); +void srcu_offline_cpu(unsigned int cpu); +#else /* #ifdef CONFIG_SRCU */ +void srcu_online_cpu(unsigned int cpu) { } +void srcu_offline_cpu(unsigned int cpu) { } +#endif /* #else #ifdef CONFIG_SRCU */ + +#endif /* #ifndef RCU_TREE_NONCORE */ diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h new file mode 100644 index 000000000..72770a551 --- /dev/null +++ b/kernel/rcu/tree_exp.h @@ -0,0 +1,811 @@ +/* + * RCU expedited grace periods + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2016 + * + * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + +#include <linux/lockdep.h> + +/* + * Record the start of an expedited grace period. + */ +static void rcu_exp_gp_seq_start(struct rcu_state *rsp) +{ + rcu_seq_start(&rsp->expedited_sequence); +} + +/* + * Return then value that expedited-grace-period counter will have + * at the end of the current grace period. + */ +static __maybe_unused unsigned long rcu_exp_gp_seq_endval(struct rcu_state *rsp) +{ + return rcu_seq_endval(&rsp->expedited_sequence); +} + +/* + * Record the end of an expedited grace period. + */ +static void rcu_exp_gp_seq_end(struct rcu_state *rsp) +{ + rcu_seq_end(&rsp->expedited_sequence); + smp_mb(); /* Ensure that consecutive grace periods serialize. */ +} + +/* + * Take a snapshot of the expedited-grace-period counter. + */ +static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp) +{ + unsigned long s; + + smp_mb(); /* Caller's modifications seen first by other CPUs. */ + s = rcu_seq_snap(&rsp->expedited_sequence); + trace_rcu_exp_grace_period(rsp->name, s, TPS("snap")); + return s; +} + +/* + * Given a counter snapshot from rcu_exp_gp_seq_snap(), return true + * if a full expedited grace period has elapsed since that snapshot + * was taken. + */ +static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s) +{ + return rcu_seq_done(&rsp->expedited_sequence, s); +} + +/* + * Reset the ->expmaskinit values in the rcu_node tree to reflect any + * recent CPU-online activity. Note that these masks are not cleared + * when CPUs go offline, so they reflect the union of all CPUs that have + * ever been online. This means that this function normally takes its + * no-work-to-do fastpath. + */ +static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp) +{ + bool done; + unsigned long flags; + unsigned long mask; + unsigned long oldmask; + int ncpus = smp_load_acquire(&rsp->ncpus); /* Order against locking. */ + struct rcu_node *rnp; + struct rcu_node *rnp_up; + + /* If no new CPUs onlined since last time, nothing to do. */ + if (likely(ncpus == rsp->ncpus_snap)) + return; + rsp->ncpus_snap = ncpus; + + /* + * Each pass through the following loop propagates newly onlined + * CPUs for the current rcu_node structure up the rcu_node tree. + */ + rcu_for_each_leaf_node(rsp, rnp) { + raw_spin_lock_irqsave_rcu_node(rnp, flags); + if (rnp->expmaskinit == rnp->expmaskinitnext) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + continue; /* No new CPUs, nothing to do. */ + } + + /* Update this node's mask, track old value for propagation. */ + oldmask = rnp->expmaskinit; + rnp->expmaskinit = rnp->expmaskinitnext; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + + /* If was already nonzero, nothing to propagate. */ + if (oldmask) + continue; + + /* Propagate the new CPU up the tree. */ + mask = rnp->grpmask; + rnp_up = rnp->parent; + done = false; + while (rnp_up) { + raw_spin_lock_irqsave_rcu_node(rnp_up, flags); + if (rnp_up->expmaskinit) + done = true; + rnp_up->expmaskinit |= mask; + raw_spin_unlock_irqrestore_rcu_node(rnp_up, flags); + if (done) + break; + mask = rnp_up->grpmask; + rnp_up = rnp_up->parent; + } + } +} + +/* + * Reset the ->expmask values in the rcu_node tree in preparation for + * a new expedited grace period. + */ +static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp) +{ + unsigned long flags; + struct rcu_node *rnp; + + sync_exp_reset_tree_hotplug(rsp); + rcu_for_each_node_breadth_first(rsp, rnp) { + raw_spin_lock_irqsave_rcu_node(rnp, flags); + WARN_ON_ONCE(rnp->expmask); + rnp->expmask = rnp->expmaskinit; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } +} + +/* + * Return non-zero if there is no RCU expedited grace period in progress + * for the specified rcu_node structure, in other words, if all CPUs and + * tasks covered by the specified rcu_node structure have done their bit + * for the current expedited grace period. Works only for preemptible + * RCU -- other RCU implementation use other means. + * + * Caller must hold the specificed rcu_node structure's ->lock + */ +static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp) +{ + raw_lockdep_assert_held_rcu_node(rnp); + + return rnp->exp_tasks == NULL && + READ_ONCE(rnp->expmask) == 0; +} + +/* + * Like sync_rcu_preempt_exp_done(), but this function assumes the caller + * doesn't hold the rcu_node's ->lock, and will acquire and release the lock + * itself + */ +static bool sync_rcu_preempt_exp_done_unlocked(struct rcu_node *rnp) +{ + unsigned long flags; + bool ret; + + raw_spin_lock_irqsave_rcu_node(rnp, flags); + ret = sync_rcu_preempt_exp_done(rnp); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + + return ret; +} + + +/* + * Report the exit from RCU read-side critical section for the last task + * that queued itself during or before the current expedited preemptible-RCU + * grace period. This event is reported either to the rcu_node structure on + * which the task was queued or to one of that rcu_node structure's ancestors, + * recursively up the tree. (Calm down, calm down, we do the recursion + * iteratively!) + * + * Caller must hold the specified rcu_node structure's ->lock. + */ +static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, + bool wake, unsigned long flags) + __releases(rnp->lock) +{ + unsigned long mask; + + for (;;) { + if (!sync_rcu_preempt_exp_done(rnp)) { + if (!rnp->expmask) + rcu_initiate_boost(rnp, flags); + else + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + break; + } + if (rnp->parent == NULL) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + if (wake) { + smp_mb(); /* EGP done before wake_up(). */ + swake_up_one(&rsp->expedited_wq); + } + break; + } + mask = rnp->grpmask; + raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled */ + rnp = rnp->parent; + raw_spin_lock_rcu_node(rnp); /* irqs already disabled */ + WARN_ON_ONCE(!(rnp->expmask & mask)); + rnp->expmask &= ~mask; + } +} + +/* + * Report expedited quiescent state for specified node. This is a + * lock-acquisition wrapper function for __rcu_report_exp_rnp(). + */ +static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp, + struct rcu_node *rnp, bool wake) +{ + unsigned long flags; + + raw_spin_lock_irqsave_rcu_node(rnp, flags); + __rcu_report_exp_rnp(rsp, rnp, wake, flags); +} + +/* + * Report expedited quiescent state for multiple CPUs, all covered by the + * specified leaf rcu_node structure. + */ +static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp, + unsigned long mask, bool wake) +{ + unsigned long flags; + + raw_spin_lock_irqsave_rcu_node(rnp, flags); + if (!(rnp->expmask & mask)) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + rnp->expmask &= ~mask; + __rcu_report_exp_rnp(rsp, rnp, wake, flags); /* Releases rnp->lock. */ +} + +/* + * Report expedited quiescent state for specified rcu_data (CPU). + */ +static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp, + bool wake) +{ + rcu_report_exp_cpu_mult(rsp, rdp->mynode, rdp->grpmask, wake); +} + +/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */ +static bool sync_exp_work_done(struct rcu_state *rsp, unsigned long s) +{ + if (rcu_exp_gp_seq_done(rsp, s)) { + trace_rcu_exp_grace_period(rsp->name, s, TPS("done")); + /* Ensure test happens before caller kfree(). */ + smp_mb__before_atomic(); /* ^^^ */ + return true; + } + return false; +} + +/* + * Funnel-lock acquisition for expedited grace periods. Returns true + * if some other task completed an expedited grace period that this task + * can piggy-back on, and with no mutex held. Otherwise, returns false + * with the mutex held, indicating that the caller must actually do the + * expedited grace period. + */ +static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s) +{ + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id()); + struct rcu_node *rnp = rdp->mynode; + struct rcu_node *rnp_root = rcu_get_root(rsp); + + /* Low-contention fastpath. */ + if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s) && + (rnp == rnp_root || + ULONG_CMP_LT(READ_ONCE(rnp_root->exp_seq_rq), s)) && + mutex_trylock(&rsp->exp_mutex)) + goto fastpath; + + /* + * Each pass through the following loop works its way up + * the rcu_node tree, returning if others have done the work or + * otherwise falls through to acquire rsp->exp_mutex. The mapping + * from CPU to rcu_node structure can be inexact, as it is just + * promoting locality and is not strictly needed for correctness. + */ + for (; rnp != NULL; rnp = rnp->parent) { + if (sync_exp_work_done(rsp, s)) + return true; + + /* Work not done, either wait here or go up. */ + spin_lock(&rnp->exp_lock); + if (ULONG_CMP_GE(rnp->exp_seq_rq, s)) { + + /* Someone else doing GP, so wait for them. */ + spin_unlock(&rnp->exp_lock); + trace_rcu_exp_funnel_lock(rsp->name, rnp->level, + rnp->grplo, rnp->grphi, + TPS("wait")); + wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], + sync_exp_work_done(rsp, s)); + return true; + } + rnp->exp_seq_rq = s; /* Followers can wait on us. */ + spin_unlock(&rnp->exp_lock); + trace_rcu_exp_funnel_lock(rsp->name, rnp->level, rnp->grplo, + rnp->grphi, TPS("nxtlvl")); + } + mutex_lock(&rsp->exp_mutex); +fastpath: + if (sync_exp_work_done(rsp, s)) { + mutex_unlock(&rsp->exp_mutex); + return true; + } + rcu_exp_gp_seq_start(rsp); + trace_rcu_exp_grace_period(rsp->name, s, TPS("start")); + return false; +} + +/* Invoked on each online non-idle CPU for expedited quiescent state. */ +static void sync_sched_exp_handler(void *data) +{ + struct rcu_data *rdp; + struct rcu_node *rnp; + struct rcu_state *rsp = data; + + rdp = this_cpu_ptr(rsp->rda); + rnp = rdp->mynode; + if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) || + __this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp)) + return; + if (rcu_is_cpu_rrupt_from_idle()) { + rcu_report_exp_rdp(&rcu_sched_state, + this_cpu_ptr(&rcu_sched_data), true); + return; + } + __this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, true); + /* Store .exp before .rcu_urgent_qs. */ + smp_store_release(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs), true); + resched_cpu(smp_processor_id()); +} + +/* Send IPI for expedited cleanup if needed at end of CPU-hotplug operation. */ +static void sync_sched_exp_online_cleanup(int cpu) +{ + struct rcu_data *rdp; + int ret; + struct rcu_node *rnp; + struct rcu_state *rsp = &rcu_sched_state; + + rdp = per_cpu_ptr(rsp->rda, cpu); + rnp = rdp->mynode; + if (!(READ_ONCE(rnp->expmask) & rdp->grpmask)) + return; + ret = smp_call_function_single(cpu, sync_sched_exp_handler, rsp, 0); + WARN_ON_ONCE(ret); +} + +/* + * Select the CPUs within the specified rcu_node that the upcoming + * expedited grace period needs to wait for. + */ +static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) +{ + int cpu; + unsigned long flags; + smp_call_func_t func; + unsigned long mask_ofl_test; + unsigned long mask_ofl_ipi; + int ret; + struct rcu_exp_work *rewp = + container_of(wp, struct rcu_exp_work, rew_work); + struct rcu_node *rnp = container_of(rewp, struct rcu_node, rew); + struct rcu_state *rsp = rewp->rew_rsp; + + func = rewp->rew_func; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + + /* Each pass checks a CPU for identity, offline, and idle. */ + mask_ofl_test = 0; + for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) { + unsigned long mask = leaf_node_cpu_bit(rnp, cpu); + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_dynticks *rdtp = per_cpu_ptr(&rcu_dynticks, cpu); + int snap; + + if (raw_smp_processor_id() == cpu || + !(rnp->qsmaskinitnext & mask)) { + mask_ofl_test |= mask; + } else { + snap = rcu_dynticks_snap(rdtp); + if (rcu_dynticks_in_eqs(snap)) + mask_ofl_test |= mask; + else + rdp->exp_dynticks_snap = snap; + } + } + mask_ofl_ipi = rnp->expmask & ~mask_ofl_test; + + /* + * Need to wait for any blocked tasks as well. Note that + * additional blocking tasks will also block the expedited GP + * until such time as the ->expmask bits are cleared. + */ + if (rcu_preempt_has_tasks(rnp)) + rnp->exp_tasks = rnp->blkd_tasks.next; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + + /* IPI the remaining CPUs for expedited quiescent state. */ + for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) { + unsigned long mask = leaf_node_cpu_bit(rnp, cpu); + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + + if (!(mask_ofl_ipi & mask)) + continue; +retry_ipi: + if (rcu_dynticks_in_eqs_since(rdp->dynticks, + rdp->exp_dynticks_snap)) { + mask_ofl_test |= mask; + continue; + } + ret = smp_call_function_single(cpu, func, rsp, 0); + if (!ret) { + mask_ofl_ipi &= ~mask; + continue; + } + /* Failed, raced with CPU hotplug operation. */ + raw_spin_lock_irqsave_rcu_node(rnp, flags); + if ((rnp->qsmaskinitnext & mask) && + (rnp->expmask & mask)) { + /* Online, so delay for a bit and try again. */ + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("selectofl")); + schedule_timeout_uninterruptible(1); + goto retry_ipi; + } + /* CPU really is offline, so we can ignore it. */ + if (!(rnp->expmask & mask)) + mask_ofl_ipi &= ~mask; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + /* Report quiescent states for those that went offline. */ + mask_ofl_test |= mask_ofl_ipi; + if (mask_ofl_test) + rcu_report_exp_cpu_mult(rsp, rnp, mask_ofl_test, false); +} + +/* + * Select the nodes that the upcoming expedited grace period needs + * to wait for. + */ +static void sync_rcu_exp_select_cpus(struct rcu_state *rsp, + smp_call_func_t func) +{ + int cpu; + struct rcu_node *rnp; + + trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("reset")); + sync_exp_reset_tree(rsp); + trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("select")); + + /* Schedule work for each leaf rcu_node structure. */ + rcu_for_each_leaf_node(rsp, rnp) { + rnp->exp_need_flush = false; + if (!READ_ONCE(rnp->expmask)) + continue; /* Avoid early boot non-existent wq. */ + rnp->rew.rew_func = func; + rnp->rew.rew_rsp = rsp; + if (!READ_ONCE(rcu_par_gp_wq) || + rcu_scheduler_active != RCU_SCHEDULER_RUNNING || + rcu_is_last_leaf_node(rsp, rnp)) { + /* No workqueues yet or last leaf, do direct call. */ + sync_rcu_exp_select_node_cpus(&rnp->rew.rew_work); + continue; + } + INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus); + preempt_disable(); + cpu = cpumask_next(rnp->grplo - 1, cpu_online_mask); + /* If all offline, queue the work on an unbound CPU. */ + if (unlikely(cpu > rnp->grphi)) + cpu = WORK_CPU_UNBOUND; + queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work); + preempt_enable(); + rnp->exp_need_flush = true; + } + + /* Wait for workqueue jobs (if any) to complete. */ + rcu_for_each_leaf_node(rsp, rnp) + if (rnp->exp_need_flush) + flush_work(&rnp->rew.rew_work); +} + +static void synchronize_sched_expedited_wait(struct rcu_state *rsp) +{ + int cpu; + unsigned long jiffies_stall; + unsigned long jiffies_start; + unsigned long mask; + int ndetected; + struct rcu_node *rnp; + struct rcu_node *rnp_root = rcu_get_root(rsp); + int ret; + + trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("startwait")); + jiffies_stall = rcu_jiffies_till_stall_check(); + jiffies_start = jiffies; + + for (;;) { + ret = swait_event_timeout_exclusive( + rsp->expedited_wq, + sync_rcu_preempt_exp_done_unlocked(rnp_root), + jiffies_stall); + if (ret > 0 || sync_rcu_preempt_exp_done_unlocked(rnp_root)) + return; + WARN_ON(ret < 0); /* workqueues should not be signaled. */ + if (rcu_cpu_stall_suppress) + continue; + panic_on_rcu_stall(); + pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {", + rsp->name); + ndetected = 0; + rcu_for_each_leaf_node(rsp, rnp) { + ndetected += rcu_print_task_exp_stall(rnp); + for_each_leaf_node_possible_cpu(rnp, cpu) { + struct rcu_data *rdp; + + mask = leaf_node_cpu_bit(rnp, cpu); + if (!(rnp->expmask & mask)) + continue; + ndetected++; + rdp = per_cpu_ptr(rsp->rda, cpu); + pr_cont(" %d-%c%c%c", cpu, + "O."[!!cpu_online(cpu)], + "o."[!!(rdp->grpmask & rnp->expmaskinit)], + "N."[!!(rdp->grpmask & rnp->expmaskinitnext)]); + } + } + pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n", + jiffies - jiffies_start, rsp->expedited_sequence, + rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]); + if (ndetected) { + pr_err("blocking rcu_node structures:"); + rcu_for_each_node_breadth_first(rsp, rnp) { + if (rnp == rnp_root) + continue; /* printed unconditionally */ + if (sync_rcu_preempt_exp_done_unlocked(rnp)) + continue; + pr_cont(" l=%u:%d-%d:%#lx/%c", + rnp->level, rnp->grplo, rnp->grphi, + rnp->expmask, + ".T"[!!rnp->exp_tasks]); + } + pr_cont("\n"); + } + rcu_for_each_leaf_node(rsp, rnp) { + for_each_leaf_node_possible_cpu(rnp, cpu) { + mask = leaf_node_cpu_bit(rnp, cpu); + if (!(rnp->expmask & mask)) + continue; + dump_cpu_task(cpu); + } + } + jiffies_stall = 3 * rcu_jiffies_till_stall_check() + 3; + } +} + +/* + * Wait for the current expedited grace period to complete, and then + * wake up everyone who piggybacked on the just-completed expedited + * grace period. Also update all the ->exp_seq_rq counters as needed + * in order to avoid counter-wrap problems. + */ +static void rcu_exp_wait_wake(struct rcu_state *rsp, unsigned long s) +{ + struct rcu_node *rnp; + + synchronize_sched_expedited_wait(rsp); + rcu_exp_gp_seq_end(rsp); + trace_rcu_exp_grace_period(rsp->name, s, TPS("end")); + + /* + * Switch over to wakeup mode, allowing the next GP, but -only- the + * next GP, to proceed. + */ + mutex_lock(&rsp->exp_wake_mutex); + + rcu_for_each_node_breadth_first(rsp, rnp) { + if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s)) { + spin_lock(&rnp->exp_lock); + /* Recheck, avoid hang in case someone just arrived. */ + if (ULONG_CMP_LT(rnp->exp_seq_rq, s)) + rnp->exp_seq_rq = s; + spin_unlock(&rnp->exp_lock); + } + smp_mb(); /* All above changes before wakeup. */ + wake_up_all(&rnp->exp_wq[rcu_seq_ctr(s) & 0x3]); + } + trace_rcu_exp_grace_period(rsp->name, s, TPS("endwake")); + mutex_unlock(&rsp->exp_wake_mutex); +} + +/* + * Common code to drive an expedited grace period forward, used by + * workqueues and mid-boot-time tasks. + */ +static void rcu_exp_sel_wait_wake(struct rcu_state *rsp, + smp_call_func_t func, unsigned long s) +{ + /* Initialize the rcu_node tree in preparation for the wait. */ + sync_rcu_exp_select_cpus(rsp, func); + + /* Wait and clean up, including waking everyone. */ + rcu_exp_wait_wake(rsp, s); +} + +/* + * Work-queue handler to drive an expedited grace period forward. + */ +static void wait_rcu_exp_gp(struct work_struct *wp) +{ + struct rcu_exp_work *rewp; + + rewp = container_of(wp, struct rcu_exp_work, rew_work); + rcu_exp_sel_wait_wake(rewp->rew_rsp, rewp->rew_func, rewp->rew_s); +} + +/* + * Given an rcu_state pointer and a smp_call_function() handler, kick + * off the specified flavor of expedited grace period. + */ +static void _synchronize_rcu_expedited(struct rcu_state *rsp, + smp_call_func_t func) +{ + struct rcu_data *rdp; + struct rcu_exp_work rew; + struct rcu_node *rnp; + unsigned long s; + + /* If expedited grace periods are prohibited, fall back to normal. */ + if (rcu_gp_is_normal()) { + wait_rcu_gp(rsp->call); + return; + } + + /* Take a snapshot of the sequence number. */ + s = rcu_exp_gp_seq_snap(rsp); + if (exp_funnel_lock(rsp, s)) + return; /* Someone else did our work for us. */ + + /* Ensure that load happens before action based on it. */ + if (unlikely(rcu_scheduler_active == RCU_SCHEDULER_INIT)) { + /* Direct call during scheduler init and early_initcalls(). */ + rcu_exp_sel_wait_wake(rsp, func, s); + } else { + /* Marshall arguments & schedule the expedited grace period. */ + rew.rew_func = func; + rew.rew_rsp = rsp; + rew.rew_s = s; + INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp); + queue_work(rcu_gp_wq, &rew.rew_work); + } + + /* Wait for expedited grace period to complete. */ + rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id()); + rnp = rcu_get_root(rsp); + wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], + sync_exp_work_done(rsp, s)); + smp_mb(); /* Workqueue actions happen before return. */ + + /* Let the next expedited grace period start. */ + mutex_unlock(&rsp->exp_mutex); +} + +/** + * synchronize_sched_expedited - Brute-force RCU-sched grace period + * + * Wait for an RCU-sched grace period to elapse, but use a "big hammer" + * approach to force the grace period to end quickly. This consumes + * significant time on all CPUs and is unfriendly to real-time workloads, + * so is thus not recommended for any sort of common-case code. In fact, + * if you are using synchronize_sched_expedited() in a loop, please + * restructure your code to batch your updates, and then use a single + * synchronize_sched() instead. + * + * This implementation can be thought of as an application of sequence + * locking to expedited grace periods, but using the sequence counter to + * determine when someone else has already done the work instead of for + * retrying readers. + */ +void synchronize_sched_expedited(void) +{ + struct rcu_state *rsp = &rcu_sched_state; + + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_sched_expedited() in RCU read-side critical section"); + + /* If only one CPU, this is automatically a grace period. */ + if (rcu_blocking_is_gp()) + return; + + _synchronize_rcu_expedited(rsp, sync_sched_exp_handler); +} +EXPORT_SYMBOL_GPL(synchronize_sched_expedited); + +#ifdef CONFIG_PREEMPT_RCU + +/* + * Remote handler for smp_call_function_single(). If there is an + * RCU read-side critical section in effect, request that the + * next rcu_read_unlock() record the quiescent state up the + * ->expmask fields in the rcu_node tree. Otherwise, immediately + * report the quiescent state. + */ +static void sync_rcu_exp_handler(void *info) +{ + struct rcu_data *rdp; + struct rcu_state *rsp = info; + struct task_struct *t = current; + + /* + * Within an RCU read-side critical section, request that the next + * rcu_read_unlock() report. Unless this RCU read-side critical + * section has already blocked, in which case it is already set + * up for the expedited grace period to wait on it. + */ + if (t->rcu_read_lock_nesting > 0 && + !t->rcu_read_unlock_special.b.blocked) { + t->rcu_read_unlock_special.b.exp_need_qs = true; + return; + } + + /* + * We are either exiting an RCU read-side critical section (negative + * values of t->rcu_read_lock_nesting) or are not in one at all + * (zero value of t->rcu_read_lock_nesting). Or we are in an RCU + * read-side critical section that blocked before this expedited + * grace period started. Either way, we can immediately report + * the quiescent state. + */ + rdp = this_cpu_ptr(rsp->rda); + rcu_report_exp_rdp(rsp, rdp, true); +} + +/** + * synchronize_rcu_expedited - Brute-force RCU grace period + * + * Wait for an RCU-preempt grace period, but expedite it. The basic + * idea is to IPI all non-idle non-nohz online CPUs. The IPI handler + * checks whether the CPU is in an RCU-preempt critical section, and + * if so, it sets a flag that causes the outermost rcu_read_unlock() + * to report the quiescent state. On the other hand, if the CPU is + * not in an RCU read-side critical section, the IPI handler reports + * the quiescent state immediately. + * + * Although this is a greate improvement over previous expedited + * implementations, it is still unfriendly to real-time workloads, so is + * thus not recommended for any sort of common-case code. In fact, if + * you are using synchronize_rcu_expedited() in a loop, please restructure + * your code to batch your updates, and then Use a single synchronize_rcu() + * instead. + */ +void synchronize_rcu_expedited(void) +{ + struct rcu_state *rsp = rcu_state_p; + + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_rcu_expedited() in RCU read-side critical section"); + + if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) + return; + _synchronize_rcu_expedited(rsp, sync_rcu_exp_handler); +} +EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); + +#else /* #ifdef CONFIG_PREEMPT_RCU */ + +/* + * Wait for an rcu-preempt grace period, but make it happen quickly. + * But because preemptible RCU does not exist, map to rcu-sched. + */ +void synchronize_rcu_expedited(void) +{ + synchronize_sched_expedited(); +} +EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); + +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h new file mode 100644 index 000000000..5f6de49dc --- /dev/null +++ b/kernel/rcu/tree_plugin.h @@ -0,0 +1,2693 @@ +/* + * Read-Copy Update mechanism for mutual exclusion (tree-based version) + * Internal non-public definitions that provide either classic + * or preemptible semantics. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright Red Hat, 2009 + * Copyright IBM Corporation, 2009 + * + * Author: Ingo Molnar <mingo@elte.hu> + * Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + +#include <linux/delay.h> +#include <linux/gfp.h> +#include <linux/oom.h> +#include <linux/sched/debug.h> +#include <linux/smpboot.h> +#include <linux/sched/isolation.h> +#include <uapi/linux/sched/types.h> +#include "../time/tick-internal.h" + +#ifdef CONFIG_RCU_BOOST + +#include "../locking/rtmutex_common.h" + +/* + * Control variables for per-CPU and per-rcu_node kthreads. These + * handle all flavors of RCU. + */ +static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); +DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); +DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); +DEFINE_PER_CPU(char, rcu_cpu_has_work); + +#else /* #ifdef CONFIG_RCU_BOOST */ + +/* + * Some architectures do not define rt_mutexes, but if !CONFIG_RCU_BOOST, + * all uses are in dead code. Provide a definition to keep the compiler + * happy, but add WARN_ON_ONCE() to complain if used in the wrong place. + * This probably needs to be excluded from -rt builds. + */ +#define rt_mutex_owner(a) ({ WARN_ON_ONCE(1); NULL; }) +#define rt_mutex_futex_unlock(x) WARN_ON_ONCE(1) + +#endif /* #else #ifdef CONFIG_RCU_BOOST */ + +#ifdef CONFIG_RCU_NOCB_CPU +static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */ +static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */ +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ + +/* + * Check the RCU kernel configuration parameters and print informative + * messages about anything out of the ordinary. + */ +static void __init rcu_bootup_announce_oddness(void) +{ + if (IS_ENABLED(CONFIG_RCU_TRACE)) + pr_info("\tRCU event tracing is enabled.\n"); + if ((IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 64) || + (!IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 32)) + pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d.\n", + RCU_FANOUT); + if (rcu_fanout_exact) + pr_info("\tHierarchical RCU autobalancing is disabled.\n"); + if (IS_ENABLED(CONFIG_RCU_FAST_NO_HZ)) + pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n"); + if (IS_ENABLED(CONFIG_PROVE_RCU)) + pr_info("\tRCU lockdep checking is enabled.\n"); + if (RCU_NUM_LVLS >= 4) + pr_info("\tFour(or more)-level hierarchy is enabled.\n"); + if (RCU_FANOUT_LEAF != 16) + pr_info("\tBuild-time adjustment of leaf fanout to %d.\n", + RCU_FANOUT_LEAF); + if (rcu_fanout_leaf != RCU_FANOUT_LEAF) + pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", + rcu_fanout_leaf); + if (nr_cpu_ids != NR_CPUS) + pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%u.\n", NR_CPUS, nr_cpu_ids); +#ifdef CONFIG_RCU_BOOST + pr_info("\tRCU priority boosting: priority %d delay %d ms.\n", + kthread_prio, CONFIG_RCU_BOOST_DELAY); +#endif + if (blimit != DEFAULT_RCU_BLIMIT) + pr_info("\tBoot-time adjustment of callback invocation limit to %ld.\n", blimit); + if (qhimark != DEFAULT_RCU_QHIMARK) + pr_info("\tBoot-time adjustment of callback high-water mark to %ld.\n", qhimark); + if (qlowmark != DEFAULT_RCU_QLOMARK) + pr_info("\tBoot-time adjustment of callback low-water mark to %ld.\n", qlowmark); + if (jiffies_till_first_fqs != ULONG_MAX) + pr_info("\tBoot-time adjustment of first FQS scan delay to %ld jiffies.\n", jiffies_till_first_fqs); + if (jiffies_till_next_fqs != ULONG_MAX) + pr_info("\tBoot-time adjustment of subsequent FQS scan delay to %ld jiffies.\n", jiffies_till_next_fqs); + if (rcu_kick_kthreads) + pr_info("\tKick kthreads if too-long grace period.\n"); + if (IS_ENABLED(CONFIG_DEBUG_OBJECTS_RCU_HEAD)) + pr_info("\tRCU callback double-/use-after-free debug enabled.\n"); + if (gp_preinit_delay) + pr_info("\tRCU debug GP pre-init slowdown %d jiffies.\n", gp_preinit_delay); + if (gp_init_delay) + pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_init_delay); + if (gp_cleanup_delay) + pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_cleanup_delay); + if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG)) + pr_info("\tRCU debug extended QS entry/exit.\n"); + rcupdate_announce_bootup_oddness(); +} + +#ifdef CONFIG_PREEMPT_RCU + +RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu); +static struct rcu_state *const rcu_state_p = &rcu_preempt_state; +static struct rcu_data __percpu *const rcu_data_p = &rcu_preempt_data; + +static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, + bool wake); +static void rcu_read_unlock_special(struct task_struct *t); + +/* + * Tell them what RCU they are running. + */ +static void __init rcu_bootup_announce(void) +{ + pr_info("Preemptible hierarchical RCU implementation.\n"); + rcu_bootup_announce_oddness(); +} + +/* Flags for rcu_preempt_ctxt_queue() decision table. */ +#define RCU_GP_TASKS 0x8 +#define RCU_EXP_TASKS 0x4 +#define RCU_GP_BLKD 0x2 +#define RCU_EXP_BLKD 0x1 + +/* + * Queues a task preempted within an RCU-preempt read-side critical + * section into the appropriate location within the ->blkd_tasks list, + * depending on the states of any ongoing normal and expedited grace + * periods. The ->gp_tasks pointer indicates which element the normal + * grace period is waiting on (NULL if none), and the ->exp_tasks pointer + * indicates which element the expedited grace period is waiting on (again, + * NULL if none). If a grace period is waiting on a given element in the + * ->blkd_tasks list, it also waits on all subsequent elements. Thus, + * adding a task to the tail of the list blocks any grace period that is + * already waiting on one of the elements. In contrast, adding a task + * to the head of the list won't block any grace period that is already + * waiting on one of the elements. + * + * This queuing is imprecise, and can sometimes make an ongoing grace + * period wait for a task that is not strictly speaking blocking it. + * Given the choice, we needlessly block a normal grace period rather than + * blocking an expedited grace period. + * + * Note that an endless sequence of expedited grace periods still cannot + * indefinitely postpone a normal grace period. Eventually, all of the + * fixed number of preempted tasks blocking the normal grace period that are + * not also blocking the expedited grace period will resume and complete + * their RCU read-side critical sections. At that point, the ->gp_tasks + * pointer will equal the ->exp_tasks pointer, at which point the end of + * the corresponding expedited grace period will also be the end of the + * normal grace period. + */ +static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp) + __releases(rnp->lock) /* But leaves rrupts disabled. */ +{ + int blkd_state = (rnp->gp_tasks ? RCU_GP_TASKS : 0) + + (rnp->exp_tasks ? RCU_EXP_TASKS : 0) + + (rnp->qsmask & rdp->grpmask ? RCU_GP_BLKD : 0) + + (rnp->expmask & rdp->grpmask ? RCU_EXP_BLKD : 0); + struct task_struct *t = current; + + raw_lockdep_assert_held_rcu_node(rnp); + WARN_ON_ONCE(rdp->mynode != rnp); + WARN_ON_ONCE(!rcu_is_leaf_node(rnp)); + /* RCU better not be waiting on newly onlined CPUs! */ + WARN_ON_ONCE(rnp->qsmaskinitnext & ~rnp->qsmaskinit & rnp->qsmask & + rdp->grpmask); + + /* + * Decide where to queue the newly blocked task. In theory, + * this could be an if-statement. In practice, when I tried + * that, it was quite messy. + */ + switch (blkd_state) { + case 0: + case RCU_EXP_TASKS: + case RCU_EXP_TASKS + RCU_GP_BLKD: + case RCU_GP_TASKS: + case RCU_GP_TASKS + RCU_EXP_TASKS: + + /* + * Blocking neither GP, or first task blocking the normal + * GP but not blocking the already-waiting expedited GP. + * Queue at the head of the list to avoid unnecessarily + * blocking the already-waiting GPs. + */ + list_add(&t->rcu_node_entry, &rnp->blkd_tasks); + break; + + case RCU_EXP_BLKD: + case RCU_GP_BLKD: + case RCU_GP_BLKD + RCU_EXP_BLKD: + case RCU_GP_TASKS + RCU_EXP_BLKD: + case RCU_GP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: + case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: + + /* + * First task arriving that blocks either GP, or first task + * arriving that blocks the expedited GP (with the normal + * GP already waiting), or a task arriving that blocks + * both GPs with both GPs already waiting. Queue at the + * tail of the list to avoid any GP waiting on any of the + * already queued tasks that are not blocking it. + */ + list_add_tail(&t->rcu_node_entry, &rnp->blkd_tasks); + break; + + case RCU_EXP_TASKS + RCU_EXP_BLKD: + case RCU_EXP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: + case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_EXP_BLKD: + + /* + * Second or subsequent task blocking the expedited GP. + * The task either does not block the normal GP, or is the + * first task blocking the normal GP. Queue just after + * the first task blocking the expedited GP. + */ + list_add(&t->rcu_node_entry, rnp->exp_tasks); + break; + + case RCU_GP_TASKS + RCU_GP_BLKD: + case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_GP_BLKD: + + /* + * Second or subsequent task blocking the normal GP. + * The task does not block the expedited GP. Queue just + * after the first task blocking the normal GP. + */ + list_add(&t->rcu_node_entry, rnp->gp_tasks); + break; + + default: + + /* Yet another exercise in excessive paranoia. */ + WARN_ON_ONCE(1); + break; + } + + /* + * We have now queued the task. If it was the first one to + * block either grace period, update the ->gp_tasks and/or + * ->exp_tasks pointers, respectively, to reference the newly + * blocked tasks. + */ + if (!rnp->gp_tasks && (blkd_state & RCU_GP_BLKD)) { + WRITE_ONCE(rnp->gp_tasks, &t->rcu_node_entry); + WARN_ON_ONCE(rnp->completedqs == rnp->gp_seq); + } + if (!rnp->exp_tasks && (blkd_state & RCU_EXP_BLKD)) + rnp->exp_tasks = &t->rcu_node_entry; + WARN_ON_ONCE(!(blkd_state & RCU_GP_BLKD) != + !(rnp->qsmask & rdp->grpmask)); + WARN_ON_ONCE(!(blkd_state & RCU_EXP_BLKD) != + !(rnp->expmask & rdp->grpmask)); + raw_spin_unlock_rcu_node(rnp); /* interrupts remain disabled. */ + + /* + * Report the quiescent state for the expedited GP. This expedited + * GP should not be able to end until we report, so there should be + * no need to check for a subsequent expedited GP. (Though we are + * still in a quiescent state in any case.) + */ + if (blkd_state & RCU_EXP_BLKD && + t->rcu_read_unlock_special.b.exp_need_qs) { + t->rcu_read_unlock_special.b.exp_need_qs = false; + rcu_report_exp_rdp(rdp->rsp, rdp, true); + } else { + WARN_ON_ONCE(t->rcu_read_unlock_special.b.exp_need_qs); + } +} + +/* + * Record a preemptible-RCU quiescent state for the specified CPU. + * Note that this does not necessarily mean that the task currently running + * on the CPU is in a quiescent state: Instead, it means that the current + * grace period need not wait on any RCU read-side critical section that + * starts later on this CPU. It also means that if the current task is + * in an RCU read-side critical section, it has already added itself to + * some leaf rcu_node structure's ->blkd_tasks list. In addition to the + * current task, there might be any number of other tasks blocked while + * in an RCU read-side critical section. + * + * Callers to this function must disable preemption. + */ +static void rcu_preempt_qs(void) +{ + RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_qs() invoked with preemption enabled!!!\n"); + if (__this_cpu_read(rcu_data_p->cpu_no_qs.s)) { + trace_rcu_grace_period(TPS("rcu_preempt"), + __this_cpu_read(rcu_data_p->gp_seq), + TPS("cpuqs")); + __this_cpu_write(rcu_data_p->cpu_no_qs.b.norm, false); + barrier(); /* Coordinate with rcu_preempt_check_callbacks(). */ + current->rcu_read_unlock_special.b.need_qs = false; + } +} + +/* + * We have entered the scheduler, and the current task might soon be + * context-switched away from. If this task is in an RCU read-side + * critical section, we will no longer be able to rely on the CPU to + * record that fact, so we enqueue the task on the blkd_tasks list. + * The task will dequeue itself when it exits the outermost enclosing + * RCU read-side critical section. Therefore, the current grace period + * cannot be permitted to complete until the blkd_tasks list entries + * predating the current grace period drain, in other words, until + * rnp->gp_tasks becomes NULL. + * + * Caller must disable interrupts. + */ +static void rcu_preempt_note_context_switch(bool preempt) +{ + struct task_struct *t = current; + struct rcu_data *rdp; + struct rcu_node *rnp; + + lockdep_assert_irqs_disabled(); + WARN_ON_ONCE(!preempt && t->rcu_read_lock_nesting > 0); + if (t->rcu_read_lock_nesting > 0 && + !t->rcu_read_unlock_special.b.blocked) { + + /* Possibly blocking in an RCU read-side critical section. */ + rdp = this_cpu_ptr(rcu_state_p->rda); + rnp = rdp->mynode; + raw_spin_lock_rcu_node(rnp); + t->rcu_read_unlock_special.b.blocked = true; + t->rcu_blocked_node = rnp; + + /* + * Verify the CPU's sanity, trace the preemption, and + * then queue the task as required based on the states + * of any ongoing and expedited grace periods. + */ + WARN_ON_ONCE((rdp->grpmask & rcu_rnp_online_cpus(rnp)) == 0); + WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); + trace_rcu_preempt_task(rdp->rsp->name, + t->pid, + (rnp->qsmask & rdp->grpmask) + ? rnp->gp_seq + : rcu_seq_snap(&rnp->gp_seq)); + rcu_preempt_ctxt_queue(rnp, rdp); + } else if (t->rcu_read_lock_nesting < 0 && + t->rcu_read_unlock_special.s) { + + /* + * Complete exit from RCU read-side critical section on + * behalf of preempted instance of __rcu_read_unlock(). + */ + rcu_read_unlock_special(t); + } + + /* + * Either we were not in an RCU read-side critical section to + * begin with, or we have now recorded that critical section + * globally. Either way, we can now note a quiescent state + * for this CPU. Again, if we were in an RCU read-side critical + * section, and if that critical section was blocking the current + * grace period, then the fact that the task has been enqueued + * means that we continue to block the current grace period. + */ + rcu_preempt_qs(); +} + +/* + * Check for preempted RCU readers blocking the current grace period + * for the specified rcu_node structure. If the caller needs a reliable + * answer, it must hold the rcu_node's ->lock. + */ +static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) +{ + return READ_ONCE(rnp->gp_tasks) != NULL; +} + +/* + * Preemptible RCU implementation for rcu_read_lock(). + * Just increment ->rcu_read_lock_nesting, shared state will be updated + * if we block. + */ +void __rcu_read_lock(void) +{ + current->rcu_read_lock_nesting++; + barrier(); /* critical section after entry code. */ +} +EXPORT_SYMBOL_GPL(__rcu_read_lock); + +/* + * Preemptible RCU implementation for rcu_read_unlock(). + * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost + * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then + * invoke rcu_read_unlock_special() to clean up after a context switch + * in an RCU read-side critical section and other special cases. + */ +void __rcu_read_unlock(void) +{ + struct task_struct *t = current; + + if (t->rcu_read_lock_nesting != 1) { + --t->rcu_read_lock_nesting; + } else { + barrier(); /* critical section before exit code. */ + t->rcu_read_lock_nesting = INT_MIN; + barrier(); /* assign before ->rcu_read_unlock_special load */ + if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s))) + rcu_read_unlock_special(t); + barrier(); /* ->rcu_read_unlock_special load before assign */ + t->rcu_read_lock_nesting = 0; + } +#ifdef CONFIG_PROVE_LOCKING + { + int rrln = READ_ONCE(t->rcu_read_lock_nesting); + + WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2); + } +#endif /* #ifdef CONFIG_PROVE_LOCKING */ +} +EXPORT_SYMBOL_GPL(__rcu_read_unlock); + +/* + * Advance a ->blkd_tasks-list pointer to the next entry, instead + * returning NULL if at the end of the list. + */ +static struct list_head *rcu_next_node_entry(struct task_struct *t, + struct rcu_node *rnp) +{ + struct list_head *np; + + np = t->rcu_node_entry.next; + if (np == &rnp->blkd_tasks) + np = NULL; + return np; +} + +/* + * Return true if the specified rcu_node structure has tasks that were + * preempted within an RCU read-side critical section. + */ +static bool rcu_preempt_has_tasks(struct rcu_node *rnp) +{ + return !list_empty(&rnp->blkd_tasks); +} + +/* + * Handle special cases during rcu_read_unlock(), such as needing to + * notify RCU core processing or task having blocked during the RCU + * read-side critical section. + */ +static void rcu_read_unlock_special(struct task_struct *t) +{ + bool empty_exp; + bool empty_norm; + bool empty_exp_now; + unsigned long flags; + struct list_head *np; + bool drop_boost_mutex = false; + struct rcu_data *rdp; + struct rcu_node *rnp; + union rcu_special special; + + /* NMI handlers cannot block and cannot safely manipulate state. */ + if (in_nmi()) + return; + + local_irq_save(flags); + + /* + * If RCU core is waiting for this CPU to exit its critical section, + * report the fact that it has exited. Because irqs are disabled, + * t->rcu_read_unlock_special cannot change. + */ + special = t->rcu_read_unlock_special; + if (special.b.need_qs) { + rcu_preempt_qs(); + t->rcu_read_unlock_special.b.need_qs = false; + if (!t->rcu_read_unlock_special.s) { + local_irq_restore(flags); + return; + } + } + + /* + * Respond to a request for an expedited grace period, but only if + * we were not preempted, meaning that we were running on the same + * CPU throughout. If we were preempted, the exp_need_qs flag + * would have been cleared at the time of the first preemption, + * and the quiescent state would be reported when we were dequeued. + */ + if (special.b.exp_need_qs) { + WARN_ON_ONCE(special.b.blocked); + t->rcu_read_unlock_special.b.exp_need_qs = false; + rdp = this_cpu_ptr(rcu_state_p->rda); + rcu_report_exp_rdp(rcu_state_p, rdp, true); + if (!t->rcu_read_unlock_special.s) { + local_irq_restore(flags); + return; + } + } + + /* Hardware IRQ handlers cannot block, complain if they get here. */ + if (in_irq() || in_serving_softirq()) { + lockdep_rcu_suspicious(__FILE__, __LINE__, + "rcu_read_unlock() from irq or softirq with blocking in critical section!!!\n"); + pr_alert("->rcu_read_unlock_special: %#x (b: %d, enq: %d nq: %d)\n", + t->rcu_read_unlock_special.s, + t->rcu_read_unlock_special.b.blocked, + t->rcu_read_unlock_special.b.exp_need_qs, + t->rcu_read_unlock_special.b.need_qs); + local_irq_restore(flags); + return; + } + + /* Clean up if blocked during RCU read-side critical section. */ + if (special.b.blocked) { + t->rcu_read_unlock_special.b.blocked = false; + + /* + * Remove this task from the list it blocked on. The task + * now remains queued on the rcu_node corresponding to the + * CPU it first blocked on, so there is no longer any need + * to loop. Retain a WARN_ON_ONCE() out of sheer paranoia. + */ + rnp = t->rcu_blocked_node; + raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ + WARN_ON_ONCE(rnp != t->rcu_blocked_node); + WARN_ON_ONCE(!rcu_is_leaf_node(rnp)); + empty_norm = !rcu_preempt_blocked_readers_cgp(rnp); + WARN_ON_ONCE(rnp->completedqs == rnp->gp_seq && + (!empty_norm || rnp->qsmask)); + empty_exp = sync_rcu_preempt_exp_done(rnp); + smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ + np = rcu_next_node_entry(t, rnp); + list_del_init(&t->rcu_node_entry); + t->rcu_blocked_node = NULL; + trace_rcu_unlock_preempted_task(TPS("rcu_preempt"), + rnp->gp_seq, t->pid); + if (&t->rcu_node_entry == rnp->gp_tasks) + WRITE_ONCE(rnp->gp_tasks, np); + if (&t->rcu_node_entry == rnp->exp_tasks) + rnp->exp_tasks = np; + if (IS_ENABLED(CONFIG_RCU_BOOST)) { + /* Snapshot ->boost_mtx ownership w/rnp->lock held. */ + drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t; + if (&t->rcu_node_entry == rnp->boost_tasks) + rnp->boost_tasks = np; + } + + /* + * If this was the last task on the current list, and if + * we aren't waiting on any CPUs, report the quiescent state. + * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, + * so we must take a snapshot of the expedited state. + */ + empty_exp_now = sync_rcu_preempt_exp_done(rnp); + if (!empty_norm && !rcu_preempt_blocked_readers_cgp(rnp)) { + trace_rcu_quiescent_state_report(TPS("preempt_rcu"), + rnp->gp_seq, + 0, rnp->qsmask, + rnp->level, + rnp->grplo, + rnp->grphi, + !!rnp->gp_tasks); + rcu_report_unblock_qs_rnp(rcu_state_p, rnp, flags); + } else { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + + /* Unboost if we were boosted. */ + if (IS_ENABLED(CONFIG_RCU_BOOST) && drop_boost_mutex) + rt_mutex_futex_unlock(&rnp->boost_mtx); + + /* + * If this was the last task on the expedited lists, + * then we need to report up the rcu_node hierarchy. + */ + if (!empty_exp && empty_exp_now) + rcu_report_exp_rnp(rcu_state_p, rnp, true); + } else { + local_irq_restore(flags); + } +} + +/* + * Dump detailed information for all tasks blocking the current RCU + * grace period on the specified rcu_node structure. + */ +static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp) +{ + unsigned long flags; + struct task_struct *t; + + raw_spin_lock_irqsave_rcu_node(rnp, flags); + if (!rcu_preempt_blocked_readers_cgp(rnp)) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + t = list_entry(rnp->gp_tasks->prev, + struct task_struct, rcu_node_entry); + list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { + /* + * We could be printing a lot while holding a spinlock. + * Avoid triggering hard lockup. + */ + touch_nmi_watchdog(); + sched_show_task(t); + } + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); +} + +/* + * Dump detailed information for all tasks blocking the current RCU + * grace period. + */ +static void rcu_print_detail_task_stall(struct rcu_state *rsp) +{ + struct rcu_node *rnp = rcu_get_root(rsp); + + rcu_print_detail_task_stall_rnp(rnp); + rcu_for_each_leaf_node(rsp, rnp) + rcu_print_detail_task_stall_rnp(rnp); +} + +static void rcu_print_task_stall_begin(struct rcu_node *rnp) +{ + pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", + rnp->level, rnp->grplo, rnp->grphi); +} + +static void rcu_print_task_stall_end(void) +{ + pr_cont("\n"); +} + +/* + * Scan the current list of tasks blocked within RCU read-side critical + * sections, printing out the tid of each. + */ +static int rcu_print_task_stall(struct rcu_node *rnp) +{ + struct task_struct *t; + int ndetected = 0; + + if (!rcu_preempt_blocked_readers_cgp(rnp)) + return 0; + rcu_print_task_stall_begin(rnp); + t = list_entry(rnp->gp_tasks->prev, + struct task_struct, rcu_node_entry); + list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { + pr_cont(" P%d", t->pid); + ndetected++; + } + rcu_print_task_stall_end(); + return ndetected; +} + +/* + * Scan the current list of tasks blocked within RCU read-side critical + * sections, printing out the tid of each that is blocking the current + * expedited grace period. + */ +static int rcu_print_task_exp_stall(struct rcu_node *rnp) +{ + struct task_struct *t; + int ndetected = 0; + + if (!rnp->exp_tasks) + return 0; + t = list_entry(rnp->exp_tasks->prev, + struct task_struct, rcu_node_entry); + list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { + pr_cont(" P%d", t->pid); + ndetected++; + } + return ndetected; +} + +/* + * Check that the list of blocked tasks for the newly completed grace + * period is in fact empty. It is a serious bug to complete a grace + * period that still has RCU readers blocked! This function must be + * invoked -before- updating this rnp's ->gp_seq, and the rnp's ->lock + * must be held by the caller. + * + * Also, if there are blocked tasks on the list, they automatically + * block the newly created grace period, so set up ->gp_tasks accordingly. + */ +static void +rcu_preempt_check_blocked_tasks(struct rcu_state *rsp, struct rcu_node *rnp) +{ + struct task_struct *t; + + RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_check_blocked_tasks() invoked with preemption enabled!!!\n"); + if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp))) + dump_blkd_tasks(rsp, rnp, 10); + if (rcu_preempt_has_tasks(rnp) && + (rnp->qsmaskinit || rnp->wait_blkd_tasks)) { + WRITE_ONCE(rnp->gp_tasks, rnp->blkd_tasks.next); + t = container_of(rnp->gp_tasks, struct task_struct, + rcu_node_entry); + trace_rcu_unlock_preempted_task(TPS("rcu_preempt-GPS"), + rnp->gp_seq, t->pid); + } + WARN_ON_ONCE(rnp->qsmask); +} + +/* + * Check for a quiescent state from the current CPU. When a task blocks, + * the task is recorded in the corresponding CPU's rcu_node structure, + * which is checked elsewhere. + * + * Caller must disable hard irqs. + */ +static void rcu_preempt_check_callbacks(void) +{ + struct rcu_state *rsp = &rcu_preempt_state; + struct task_struct *t = current; + + if (t->rcu_read_lock_nesting == 0) { + rcu_preempt_qs(); + return; + } + if (t->rcu_read_lock_nesting > 0 && + __this_cpu_read(rcu_data_p->core_needs_qs) && + __this_cpu_read(rcu_data_p->cpu_no_qs.b.norm) && + !t->rcu_read_unlock_special.b.need_qs && + time_after(jiffies, rsp->gp_start + HZ)) + t->rcu_read_unlock_special.b.need_qs = true; +} + +/** + * call_rcu() - Queue an RCU callback for invocation after a grace period. + * @head: structure to be used for queueing the RCU updates. + * @func: actual callback function to be invoked after the grace period + * + * The callback function will be invoked some time after a full grace + * period elapses, in other words after all pre-existing RCU read-side + * critical sections have completed. However, the callback function + * might well execute concurrently with RCU read-side critical sections + * that started after call_rcu() was invoked. RCU read-side critical + * sections are delimited by rcu_read_lock() and rcu_read_unlock(), + * and may be nested. + * + * Note that all CPUs must agree that the grace period extended beyond + * all pre-existing RCU read-side critical section. On systems with more + * than one CPU, this means that when "func()" is invoked, each CPU is + * guaranteed to have executed a full memory barrier since the end of its + * last RCU read-side critical section whose beginning preceded the call + * to call_rcu(). It also means that each CPU executing an RCU read-side + * critical section that continues beyond the start of "func()" must have + * executed a memory barrier after the call_rcu() but before the beginning + * of that RCU read-side critical section. Note that these guarantees + * include CPUs that are offline, idle, or executing in user mode, as + * well as CPUs that are executing in the kernel. + * + * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the + * resulting RCU callback function "func()", then both CPU A and CPU B are + * guaranteed to execute a full memory barrier during the time interval + * between the call to call_rcu() and the invocation of "func()" -- even + * if CPU A and CPU B are the same CPU (but again only if the system has + * more than one CPU). + */ +void call_rcu(struct rcu_head *head, rcu_callback_t func) +{ + __call_rcu(head, func, rcu_state_p, -1, 0); +} +EXPORT_SYMBOL_GPL(call_rcu); + +/** + * synchronize_rcu - wait until a grace period has elapsed. + * + * Control will return to the caller some time after a full grace + * period has elapsed, in other words after all currently executing RCU + * read-side critical sections have completed. Note, however, that + * upon return from synchronize_rcu(), the caller might well be executing + * concurrently with new RCU read-side critical sections that began while + * synchronize_rcu() was waiting. RCU read-side critical sections are + * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. + * + * See the description of synchronize_sched() for more detailed + * information on memory-ordering guarantees. However, please note + * that -only- the memory-ordering guarantees apply. For example, + * synchronize_rcu() is -not- guaranteed to wait on things like code + * protected by preempt_disable(), instead, synchronize_rcu() is -only- + * guaranteed to wait on RCU read-side critical sections, that is, sections + * of code protected by rcu_read_lock(). + */ +void synchronize_rcu(void) +{ + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_rcu() in RCU read-side critical section"); + if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) + return; + if (rcu_gp_is_expedited()) + synchronize_rcu_expedited(); + else + wait_rcu_gp(call_rcu); +} +EXPORT_SYMBOL_GPL(synchronize_rcu); + +/** + * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. + * + * Note that this primitive does not necessarily wait for an RCU grace period + * to complete. For example, if there are no RCU callbacks queued anywhere + * in the system, then rcu_barrier() is within its rights to return + * immediately, without waiting for anything, much less an RCU grace period. + */ +void rcu_barrier(void) +{ + _rcu_barrier(rcu_state_p); +} +EXPORT_SYMBOL_GPL(rcu_barrier); + +/* + * Initialize preemptible RCU's state structures. + */ +static void __init __rcu_init_preempt(void) +{ + rcu_init_one(rcu_state_p); +} + +/* + * Check for a task exiting while in a preemptible-RCU read-side + * critical section, clean up if so. No need to issue warnings, + * as debug_check_no_locks_held() already does this if lockdep + * is enabled. + */ +void exit_rcu(void) +{ + struct task_struct *t = current; + + if (likely(list_empty(¤t->rcu_node_entry))) + return; + t->rcu_read_lock_nesting = 1; + barrier(); + t->rcu_read_unlock_special.b.blocked = true; + __rcu_read_unlock(); +} + +/* + * Dump the blocked-tasks state, but limit the list dump to the + * specified number of elements. + */ +static void +dump_blkd_tasks(struct rcu_state *rsp, struct rcu_node *rnp, int ncheck) +{ + int cpu; + int i; + struct list_head *lhp; + bool onl; + struct rcu_data *rdp; + struct rcu_node *rnp1; + + raw_lockdep_assert_held_rcu_node(rnp); + pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n", + __func__, rnp->grplo, rnp->grphi, rnp->level, + (long)rnp->gp_seq, (long)rnp->completedqs); + for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent) + pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx\n", + __func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext); + pr_info("%s: ->gp_tasks %p ->boost_tasks %p ->exp_tasks %p\n", + __func__, READ_ONCE(rnp->gp_tasks), rnp->boost_tasks, + rnp->exp_tasks); + pr_info("%s: ->blkd_tasks", __func__); + i = 0; + list_for_each(lhp, &rnp->blkd_tasks) { + pr_cont(" %p", lhp); + if (++i >= 10) + break; + } + pr_cont("\n"); + for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) { + rdp = per_cpu_ptr(rsp->rda, cpu); + onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp)); + pr_info("\t%d: %c online: %ld(%d) offline: %ld(%d)\n", + cpu, ".o"[onl], + (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags, + (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags); + } +} + +#else /* #ifdef CONFIG_PREEMPT_RCU */ + +static struct rcu_state *const rcu_state_p = &rcu_sched_state; + +/* + * Tell them what RCU they are running. + */ +static void __init rcu_bootup_announce(void) +{ + pr_info("Hierarchical RCU implementation.\n"); + rcu_bootup_announce_oddness(); +} + +/* + * Because preemptible RCU does not exist, we never have to check for + * CPUs being in quiescent states. + */ +static void rcu_preempt_note_context_switch(bool preempt) +{ +} + +/* + * Because preemptible RCU does not exist, there are never any preempted + * RCU readers. + */ +static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) +{ + return 0; +} + +/* + * Because there is no preemptible RCU, there can be no readers blocked. + */ +static bool rcu_preempt_has_tasks(struct rcu_node *rnp) +{ + return false; +} + +/* + * Because preemptible RCU does not exist, we never have to check for + * tasks blocked within RCU read-side critical sections. + */ +static void rcu_print_detail_task_stall(struct rcu_state *rsp) +{ +} + +/* + * Because preemptible RCU does not exist, we never have to check for + * tasks blocked within RCU read-side critical sections. + */ +static int rcu_print_task_stall(struct rcu_node *rnp) +{ + return 0; +} + +/* + * Because preemptible RCU does not exist, we never have to check for + * tasks blocked within RCU read-side critical sections that are + * blocking the current expedited grace period. + */ +static int rcu_print_task_exp_stall(struct rcu_node *rnp) +{ + return 0; +} + +/* + * Because there is no preemptible RCU, there can be no readers blocked, + * so there is no need to check for blocked tasks. So check only for + * bogus qsmask values. + */ +static void +rcu_preempt_check_blocked_tasks(struct rcu_state *rsp, struct rcu_node *rnp) +{ + WARN_ON_ONCE(rnp->qsmask); +} + +/* + * Because preemptible RCU does not exist, it never has any callbacks + * to check. + */ +static void rcu_preempt_check_callbacks(void) +{ +} + +/* + * Because preemptible RCU does not exist, rcu_barrier() is just + * another name for rcu_barrier_sched(). + */ +void rcu_barrier(void) +{ + rcu_barrier_sched(); +} +EXPORT_SYMBOL_GPL(rcu_barrier); + +/* + * Because preemptible RCU does not exist, it need not be initialized. + */ +static void __init __rcu_init_preempt(void) +{ +} + +/* + * Because preemptible RCU does not exist, tasks cannot possibly exit + * while in preemptible RCU read-side critical sections. + */ +void exit_rcu(void) +{ +} + +/* + * Dump the guaranteed-empty blocked-tasks state. Trust but verify. + */ +static void +dump_blkd_tasks(struct rcu_state *rsp, struct rcu_node *rnp, int ncheck) +{ + WARN_ON_ONCE(!list_empty(&rnp->blkd_tasks)); +} + +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ + +#ifdef CONFIG_RCU_BOOST + +static void rcu_wake_cond(struct task_struct *t, int status) +{ + /* + * If the thread is yielding, only wake it when this + * is invoked from idle + */ + if (status != RCU_KTHREAD_YIELDING || is_idle_task(current)) + wake_up_process(t); +} + +/* + * Carry out RCU priority boosting on the task indicated by ->exp_tasks + * or ->boost_tasks, advancing the pointer to the next task in the + * ->blkd_tasks list. + * + * Note that irqs must be enabled: boosting the task can block. + * Returns 1 if there are more tasks needing to be boosted. + */ +static int rcu_boost(struct rcu_node *rnp) +{ + unsigned long flags; + struct task_struct *t; + struct list_head *tb; + + if (READ_ONCE(rnp->exp_tasks) == NULL && + READ_ONCE(rnp->boost_tasks) == NULL) + return 0; /* Nothing left to boost. */ + + raw_spin_lock_irqsave_rcu_node(rnp, flags); + + /* + * Recheck under the lock: all tasks in need of boosting + * might exit their RCU read-side critical sections on their own. + */ + if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return 0; + } + + /* + * Preferentially boost tasks blocking expedited grace periods. + * This cannot starve the normal grace periods because a second + * expedited grace period must boost all blocked tasks, including + * those blocking the pre-existing normal grace period. + */ + if (rnp->exp_tasks != NULL) + tb = rnp->exp_tasks; + else + tb = rnp->boost_tasks; + + /* + * We boost task t by manufacturing an rt_mutex that appears to + * be held by task t. We leave a pointer to that rt_mutex where + * task t can find it, and task t will release the mutex when it + * exits its outermost RCU read-side critical section. Then + * simply acquiring this artificial rt_mutex will boost task + * t's priority. (Thanks to tglx for suggesting this approach!) + * + * Note that task t must acquire rnp->lock to remove itself from + * the ->blkd_tasks list, which it will do from exit() if from + * nowhere else. We therefore are guaranteed that task t will + * stay around at least until we drop rnp->lock. Note that + * rnp->lock also resolves races between our priority boosting + * and task t's exiting its outermost RCU read-side critical + * section. + */ + t = container_of(tb, struct task_struct, rcu_node_entry); + rt_mutex_init_proxy_locked(&rnp->boost_mtx, t); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + /* Lock only for side effect: boosts task t's priority. */ + rt_mutex_lock(&rnp->boost_mtx); + rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ + + return READ_ONCE(rnp->exp_tasks) != NULL || + READ_ONCE(rnp->boost_tasks) != NULL; +} + +/* + * Priority-boosting kthread, one per leaf rcu_node. + */ +static int rcu_boost_kthread(void *arg) +{ + struct rcu_node *rnp = (struct rcu_node *)arg; + int spincnt = 0; + int more2boost; + + trace_rcu_utilization(TPS("Start boost kthread@init")); + for (;;) { + rnp->boost_kthread_status = RCU_KTHREAD_WAITING; + trace_rcu_utilization(TPS("End boost kthread@rcu_wait")); + rcu_wait(rnp->boost_tasks || rnp->exp_tasks); + trace_rcu_utilization(TPS("Start boost kthread@rcu_wait")); + rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; + more2boost = rcu_boost(rnp); + if (more2boost) + spincnt++; + else + spincnt = 0; + if (spincnt > 10) { + rnp->boost_kthread_status = RCU_KTHREAD_YIELDING; + trace_rcu_utilization(TPS("End boost kthread@rcu_yield")); + schedule_timeout_interruptible(2); + trace_rcu_utilization(TPS("Start boost kthread@rcu_yield")); + spincnt = 0; + } + } + /* NOTREACHED */ + trace_rcu_utilization(TPS("End boost kthread@notreached")); + return 0; +} + +/* + * Check to see if it is time to start boosting RCU readers that are + * blocking the current grace period, and, if so, tell the per-rcu_node + * kthread to start boosting them. If there is an expedited grace + * period in progress, it is always time to boost. + * + * The caller must hold rnp->lock, which this function releases. + * The ->boost_kthread_task is immortal, so we don't need to worry + * about it going away. + */ +static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) + __releases(rnp->lock) +{ + struct task_struct *t; + + raw_lockdep_assert_held_rcu_node(rnp); + if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + if (rnp->exp_tasks != NULL || + (rnp->gp_tasks != NULL && + rnp->boost_tasks == NULL && + rnp->qsmask == 0 && + ULONG_CMP_GE(jiffies, rnp->boost_time))) { + if (rnp->exp_tasks == NULL) + rnp->boost_tasks = rnp->gp_tasks; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + t = rnp->boost_kthread_task; + if (t) + rcu_wake_cond(t, rnp->boost_kthread_status); + } else { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } +} + +/* + * Wake up the per-CPU kthread to invoke RCU callbacks. + */ +static void invoke_rcu_callbacks_kthread(void) +{ + unsigned long flags; + + local_irq_save(flags); + __this_cpu_write(rcu_cpu_has_work, 1); + if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && + current != __this_cpu_read(rcu_cpu_kthread_task)) { + rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), + __this_cpu_read(rcu_cpu_kthread_status)); + } + local_irq_restore(flags); +} + +/* + * Is the current CPU running the RCU-callbacks kthread? + * Caller must have preemption disabled. + */ +static bool rcu_is_callbacks_kthread(void) +{ + return __this_cpu_read(rcu_cpu_kthread_task) == current; +} + +#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) + +/* + * Do priority-boost accounting for the start of a new grace period. + */ +static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) +{ + rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; +} + +/* + * Create an RCU-boost kthread for the specified node if one does not + * already exist. We only create this kthread for preemptible RCU. + * Returns zero if all is well, a negated errno otherwise. + */ +static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, + struct rcu_node *rnp) +{ + int rnp_index = rnp - &rsp->node[0]; + unsigned long flags; + struct sched_param sp; + struct task_struct *t; + + if (rcu_state_p != rsp) + return 0; + + if (!rcu_scheduler_fully_active || rcu_rnp_online_cpus(rnp) == 0) + return 0; + + rsp->boost = 1; + if (rnp->boost_kthread_task != NULL) + return 0; + t = kthread_create(rcu_boost_kthread, (void *)rnp, + "rcub/%d", rnp_index); + if (IS_ERR(t)) + return PTR_ERR(t); + raw_spin_lock_irqsave_rcu_node(rnp, flags); + rnp->boost_kthread_task = t; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + sp.sched_priority = kthread_prio; + sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); + wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ + return 0; +} + +static void rcu_kthread_do_work(void) +{ + rcu_do_batch(&rcu_sched_state, this_cpu_ptr(&rcu_sched_data)); + rcu_do_batch(&rcu_bh_state, this_cpu_ptr(&rcu_bh_data)); + rcu_do_batch(&rcu_preempt_state, this_cpu_ptr(&rcu_preempt_data)); +} + +static void rcu_cpu_kthread_setup(unsigned int cpu) +{ + struct sched_param sp; + + sp.sched_priority = kthread_prio; + sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); +} + +static void rcu_cpu_kthread_park(unsigned int cpu) +{ + per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; +} + +static int rcu_cpu_kthread_should_run(unsigned int cpu) +{ + return __this_cpu_read(rcu_cpu_has_work); +} + +/* + * Per-CPU kernel thread that invokes RCU callbacks. This replaces the + * RCU softirq used in flavors and configurations of RCU that do not + * support RCU priority boosting. + */ +static void rcu_cpu_kthread(unsigned int cpu) +{ + unsigned int *statusp = this_cpu_ptr(&rcu_cpu_kthread_status); + char work, *workp = this_cpu_ptr(&rcu_cpu_has_work); + int spincnt; + + for (spincnt = 0; spincnt < 10; spincnt++) { + trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait")); + local_bh_disable(); + *statusp = RCU_KTHREAD_RUNNING; + this_cpu_inc(rcu_cpu_kthread_loops); + local_irq_disable(); + work = *workp; + *workp = 0; + local_irq_enable(); + if (work) + rcu_kthread_do_work(); + local_bh_enable(); + if (*workp == 0) { + trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); + *statusp = RCU_KTHREAD_WAITING; + return; + } + } + *statusp = RCU_KTHREAD_YIELDING; + trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield")); + schedule_timeout_interruptible(2); + trace_rcu_utilization(TPS("End CPU kthread@rcu_yield")); + *statusp = RCU_KTHREAD_WAITING; +} + +/* + * Set the per-rcu_node kthread's affinity to cover all CPUs that are + * served by the rcu_node in question. The CPU hotplug lock is still + * held, so the value of rnp->qsmaskinit will be stable. + * + * We don't include outgoingcpu in the affinity set, use -1 if there is + * no outgoing CPU. If there are no CPUs left in the affinity set, + * this function allows the kthread to execute on any CPU. + */ +static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) +{ + struct task_struct *t = rnp->boost_kthread_task; + unsigned long mask = rcu_rnp_online_cpus(rnp); + cpumask_var_t cm; + int cpu; + + if (!t) + return; + if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) + return; + for_each_leaf_node_possible_cpu(rnp, cpu) + if ((mask & leaf_node_cpu_bit(rnp, cpu)) && + cpu != outgoingcpu) + cpumask_set_cpu(cpu, cm); + if (cpumask_weight(cm) == 0) + cpumask_setall(cm); + set_cpus_allowed_ptr(t, cm); + free_cpumask_var(cm); +} + +static struct smp_hotplug_thread rcu_cpu_thread_spec = { + .store = &rcu_cpu_kthread_task, + .thread_should_run = rcu_cpu_kthread_should_run, + .thread_fn = rcu_cpu_kthread, + .thread_comm = "rcuc/%u", + .setup = rcu_cpu_kthread_setup, + .park = rcu_cpu_kthread_park, +}; + +/* + * Spawn boost kthreads -- called as soon as the scheduler is running. + */ +static void __init rcu_spawn_boost_kthreads(void) +{ + struct rcu_node *rnp; + int cpu; + + for_each_possible_cpu(cpu) + per_cpu(rcu_cpu_has_work, cpu) = 0; + BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); + rcu_for_each_leaf_node(rcu_state_p, rnp) + (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); +} + +static void rcu_prepare_kthreads(int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); + struct rcu_node *rnp = rdp->mynode; + + /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ + if (rcu_scheduler_fully_active) + (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); +} + +#else /* #ifdef CONFIG_RCU_BOOST */ + +static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) + __releases(rnp->lock) +{ + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); +} + +static void invoke_rcu_callbacks_kthread(void) +{ + WARN_ON_ONCE(1); +} + +static bool rcu_is_callbacks_kthread(void) +{ + return false; +} + +static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) +{ +} + +static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) +{ +} + +static void __init rcu_spawn_boost_kthreads(void) +{ +} + +static void rcu_prepare_kthreads(int cpu) +{ +} + +#endif /* #else #ifdef CONFIG_RCU_BOOST */ + +#if !defined(CONFIG_RCU_FAST_NO_HZ) + +/* + * Check to see if any future RCU-related work will need to be done + * by the current CPU, even if none need be done immediately, returning + * 1 if so. This function is part of the RCU implementation; it is -not- + * an exported member of the RCU API. + * + * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs + * any flavor of RCU. + */ +int rcu_needs_cpu(u64 basemono, u64 *nextevt) +{ + *nextevt = KTIME_MAX; + return rcu_cpu_has_callbacks(NULL); +} + +/* + * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up + * after it. + */ +static void rcu_cleanup_after_idle(void) +{ +} + +/* + * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, + * is nothing. + */ +static void rcu_prepare_for_idle(void) +{ +} + +/* + * Don't bother keeping a running count of the number of RCU callbacks + * posted because CONFIG_RCU_FAST_NO_HZ=n. + */ +static void rcu_idle_count_callbacks_posted(void) +{ +} + +#else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ + +/* + * This code is invoked when a CPU goes idle, at which point we want + * to have the CPU do everything required for RCU so that it can enter + * the energy-efficient dyntick-idle mode. This is handled by a + * state machine implemented by rcu_prepare_for_idle() below. + * + * The following three proprocessor symbols control this state machine: + * + * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted + * to sleep in dyntick-idle mode with RCU callbacks pending. This + * is sized to be roughly one RCU grace period. Those energy-efficiency + * benchmarkers who might otherwise be tempted to set this to a large + * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your + * system. And if you are -that- concerned about energy efficiency, + * just power the system down and be done with it! + * RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is + * permitted to sleep in dyntick-idle mode with only lazy RCU + * callbacks pending. Setting this too high can OOM your system. + * + * The values below work well in practice. If future workloads require + * adjustment, they can be converted into kernel config parameters, though + * making the state machine smarter might be a better option. + */ +#define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ +#define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ + +static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY; +module_param(rcu_idle_gp_delay, int, 0644); +static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY; +module_param(rcu_idle_lazy_gp_delay, int, 0644); + +/* + * Try to advance callbacks for all flavors of RCU on the current CPU, but + * only if it has been awhile since the last time we did so. Afterwards, + * if there are any callbacks ready for immediate invocation, return true. + */ +static bool __maybe_unused rcu_try_advance_all_cbs(void) +{ + bool cbs_ready = false; + struct rcu_data *rdp; + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + struct rcu_node *rnp; + struct rcu_state *rsp; + + /* Exit early if we advanced recently. */ + if (jiffies == rdtp->last_advance_all) + return false; + rdtp->last_advance_all = jiffies; + + for_each_rcu_flavor(rsp) { + rdp = this_cpu_ptr(rsp->rda); + rnp = rdp->mynode; + + /* + * Don't bother checking unless a grace period has + * completed since we last checked and there are + * callbacks not yet ready to invoke. + */ + if ((rcu_seq_completed_gp(rdp->gp_seq, + rcu_seq_current(&rnp->gp_seq)) || + unlikely(READ_ONCE(rdp->gpwrap))) && + rcu_segcblist_pend_cbs(&rdp->cblist)) + note_gp_changes(rsp, rdp); + + if (rcu_segcblist_ready_cbs(&rdp->cblist)) + cbs_ready = true; + } + return cbs_ready; +} + +/* + * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready + * to invoke. If the CPU has callbacks, try to advance them. Tell the + * caller to set the timeout based on whether or not there are non-lazy + * callbacks. + * + * The caller must have disabled interrupts. + */ +int rcu_needs_cpu(u64 basemono, u64 *nextevt) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + unsigned long dj; + + lockdep_assert_irqs_disabled(); + + /* Snapshot to detect later posting of non-lazy callback. */ + rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; + + /* If no callbacks, RCU doesn't need the CPU. */ + if (!rcu_cpu_has_callbacks(&rdtp->all_lazy)) { + *nextevt = KTIME_MAX; + return 0; + } + + /* Attempt to advance callbacks. */ + if (rcu_try_advance_all_cbs()) { + /* Some ready to invoke, so initiate later invocation. */ + invoke_rcu_core(); + return 1; + } + rdtp->last_accelerate = jiffies; + + /* Request timer delay depending on laziness, and round. */ + if (!rdtp->all_lazy) { + dj = round_up(rcu_idle_gp_delay + jiffies, + rcu_idle_gp_delay) - jiffies; + } else { + dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; + } + *nextevt = basemono + dj * TICK_NSEC; + return 0; +} + +/* + * Prepare a CPU for idle from an RCU perspective. The first major task + * is to sense whether nohz mode has been enabled or disabled via sysfs. + * The second major task is to check to see if a non-lazy callback has + * arrived at a CPU that previously had only lazy callbacks. The third + * major task is to accelerate (that is, assign grace-period numbers to) + * any recently arrived callbacks. + * + * The caller must have disabled interrupts. + */ +static void rcu_prepare_for_idle(void) +{ + bool needwake; + struct rcu_data *rdp; + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + struct rcu_node *rnp; + struct rcu_state *rsp; + int tne; + + lockdep_assert_irqs_disabled(); + if (rcu_is_nocb_cpu(smp_processor_id())) + return; + + /* Handle nohz enablement switches conservatively. */ + tne = READ_ONCE(tick_nohz_active); + if (tne != rdtp->tick_nohz_enabled_snap) { + if (rcu_cpu_has_callbacks(NULL)) + invoke_rcu_core(); /* force nohz to see update. */ + rdtp->tick_nohz_enabled_snap = tne; + return; + } + if (!tne) + return; + + /* + * If a non-lazy callback arrived at a CPU having only lazy + * callbacks, invoke RCU core for the side-effect of recalculating + * idle duration on re-entry to idle. + */ + if (rdtp->all_lazy && + rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) { + rdtp->all_lazy = false; + rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; + invoke_rcu_core(); + return; + } + + /* + * If we have not yet accelerated this jiffy, accelerate all + * callbacks on this CPU. + */ + if (rdtp->last_accelerate == jiffies) + return; + rdtp->last_accelerate = jiffies; + for_each_rcu_flavor(rsp) { + rdp = this_cpu_ptr(rsp->rda); + if (!rcu_segcblist_pend_cbs(&rdp->cblist)) + continue; + rnp = rdp->mynode; + raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ + needwake = rcu_accelerate_cbs(rsp, rnp, rdp); + raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ + if (needwake) + rcu_gp_kthread_wake(rsp); + } +} + +/* + * Clean up for exit from idle. Attempt to advance callbacks based on + * any grace periods that elapsed while the CPU was idle, and if any + * callbacks are now ready to invoke, initiate invocation. + */ +static void rcu_cleanup_after_idle(void) +{ + lockdep_assert_irqs_disabled(); + if (rcu_is_nocb_cpu(smp_processor_id())) + return; + if (rcu_try_advance_all_cbs()) + invoke_rcu_core(); +} + +/* + * Keep a running count of the number of non-lazy callbacks posted + * on this CPU. This running counter (which is never decremented) allows + * rcu_prepare_for_idle() to detect when something out of the idle loop + * posts a callback, even if an equal number of callbacks are invoked. + * Of course, callbacks should only be posted from within a trace event + * designed to be called from idle or from within RCU_NONIDLE(). + */ +static void rcu_idle_count_callbacks_posted(void) +{ + __this_cpu_add(rcu_dynticks.nonlazy_posted, 1); +} + +/* + * Data for flushing lazy RCU callbacks at OOM time. + */ +static atomic_t oom_callback_count; +static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq); + +/* + * RCU OOM callback -- decrement the outstanding count and deliver the + * wake-up if we are the last one. + */ +static void rcu_oom_callback(struct rcu_head *rhp) +{ + if (atomic_dec_and_test(&oom_callback_count)) + wake_up(&oom_callback_wq); +} + +/* + * Post an rcu_oom_notify callback on the current CPU if it has at + * least one lazy callback. This will unnecessarily post callbacks + * to CPUs that already have a non-lazy callback at the end of their + * callback list, but this is an infrequent operation, so accept some + * extra overhead to keep things simple. + */ +static void rcu_oom_notify_cpu(void *unused) +{ + struct rcu_state *rsp; + struct rcu_data *rdp; + + for_each_rcu_flavor(rsp) { + rdp = raw_cpu_ptr(rsp->rda); + if (rcu_segcblist_n_lazy_cbs(&rdp->cblist)) { + atomic_inc(&oom_callback_count); + rsp->call(&rdp->oom_head, rcu_oom_callback); + } + } +} + +/* + * If low on memory, ensure that each CPU has a non-lazy callback. + * This will wake up CPUs that have only lazy callbacks, in turn + * ensuring that they free up the corresponding memory in a timely manner. + * Because an uncertain amount of memory will be freed in some uncertain + * timeframe, we do not claim to have freed anything. + */ +static int rcu_oom_notify(struct notifier_block *self, + unsigned long notused, void *nfreed) +{ + int cpu; + + /* Wait for callbacks from earlier instance to complete. */ + wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0); + smp_mb(); /* Ensure callback reuse happens after callback invocation. */ + + /* + * Prevent premature wakeup: ensure that all increments happen + * before there is a chance of the counter reaching zero. + */ + atomic_set(&oom_callback_count, 1); + + for_each_online_cpu(cpu) { + smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1); + cond_resched_tasks_rcu_qs(); + } + + /* Unconditionally decrement: no need to wake ourselves up. */ + atomic_dec(&oom_callback_count); + + return NOTIFY_OK; +} + +static struct notifier_block rcu_oom_nb = { + .notifier_call = rcu_oom_notify +}; + +static int __init rcu_register_oom_notifier(void) +{ + register_oom_notifier(&rcu_oom_nb); + return 0; +} +early_initcall(rcu_register_oom_notifier); + +#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ + +#ifdef CONFIG_RCU_FAST_NO_HZ + +static void print_cpu_stall_fast_no_hz(char *cp, int cpu) +{ + struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); + unsigned long nlpd = rdtp->nonlazy_posted - rdtp->nonlazy_posted_snap; + + sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c", + rdtp->last_accelerate & 0xffff, jiffies & 0xffff, + ulong2long(nlpd), + rdtp->all_lazy ? 'L' : '.', + rdtp->tick_nohz_enabled_snap ? '.' : 'D'); +} + +#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ + +static void print_cpu_stall_fast_no_hz(char *cp, int cpu) +{ + *cp = '\0'; +} + +#endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */ + +/* Initiate the stall-info list. */ +static void print_cpu_stall_info_begin(void) +{ + pr_cont("\n"); +} + +/* + * Print out diagnostic information for the specified stalled CPU. + * + * If the specified CPU is aware of the current RCU grace period + * (flavor specified by rsp), then print the number of scheduling + * clock interrupts the CPU has taken during the time that it has + * been aware. Otherwise, print the number of RCU grace periods + * that this CPU is ignorant of, for example, "1" if the CPU was + * aware of the previous grace period. + * + * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info. + */ +static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) +{ + unsigned long delta; + char fast_no_hz[72]; + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_dynticks *rdtp = rdp->dynticks; + char *ticks_title; + unsigned long ticks_value; + + /* + * We could be printing a lot while holding a spinlock. Avoid + * triggering hard lockup. + */ + touch_nmi_watchdog(); + + ticks_value = rcu_seq_ctr(rsp->gp_seq - rdp->gp_seq); + if (ticks_value) { + ticks_title = "GPs behind"; + } else { + ticks_title = "ticks this GP"; + ticks_value = rdp->ticks_this_gp; + } + print_cpu_stall_fast_no_hz(fast_no_hz, cpu); + delta = rcu_seq_ctr(rdp->mynode->gp_seq - rdp->rcu_iw_gp_seq); + pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%03x/%ld/%#lx softirq=%u/%u fqs=%ld %s\n", + cpu, + "O."[!!cpu_online(cpu)], + "o."[!!(rdp->grpmask & rdp->mynode->qsmaskinit)], + "N."[!!(rdp->grpmask & rdp->mynode->qsmaskinitnext)], + !IS_ENABLED(CONFIG_IRQ_WORK) ? '?' : + rdp->rcu_iw_pending ? (int)min(delta, 9UL) + '0' : + "!."[!delta], + ticks_value, ticks_title, + rcu_dynticks_snap(rdtp) & 0xfff, + rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting, + rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu), + READ_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart, + fast_no_hz); +} + +/* Terminate the stall-info list. */ +static void print_cpu_stall_info_end(void) +{ + pr_err("\t"); +} + +/* Zero ->ticks_this_gp for all flavors of RCU. */ +static void zero_cpu_stall_ticks(struct rcu_data *rdp) +{ + rdp->ticks_this_gp = 0; + rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id()); +} + +/* Increment ->ticks_this_gp for all flavors of RCU. */ +static void increment_cpu_stall_ticks(void) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + raw_cpu_inc(rsp->rda->ticks_this_gp); +} + +#ifdef CONFIG_RCU_NOCB_CPU + +/* + * Offload callback processing from the boot-time-specified set of CPUs + * specified by rcu_nocb_mask. For each CPU in the set, there is a + * kthread created that pulls the callbacks from the corresponding CPU, + * waits for a grace period to elapse, and invokes the callbacks. + * The no-CBs CPUs do a wake_up() on their kthread when they insert + * a callback into any empty list, unless the rcu_nocb_poll boot parameter + * has been specified, in which case each kthread actively polls its + * CPU. (Which isn't so great for energy efficiency, but which does + * reduce RCU's overhead on that CPU.) + * + * This is intended to be used in conjunction with Frederic Weisbecker's + * adaptive-idle work, which would seriously reduce OS jitter on CPUs + * running CPU-bound user-mode computations. + * + * Offloading of callback processing could also in theory be used as + * an energy-efficiency measure because CPUs with no RCU callbacks + * queued are more aggressive about entering dyntick-idle mode. + */ + + +/* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */ +static int __init rcu_nocb_setup(char *str) +{ + alloc_bootmem_cpumask_var(&rcu_nocb_mask); + cpulist_parse(str, rcu_nocb_mask); + return 1; +} +__setup("rcu_nocbs=", rcu_nocb_setup); + +static int __init parse_rcu_nocb_poll(char *arg) +{ + rcu_nocb_poll = true; + return 0; +} +early_param("rcu_nocb_poll", parse_rcu_nocb_poll); + +/* + * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended + * grace period. + */ +static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq) +{ + swake_up_all(sq); +} + +static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp) +{ + return &rnp->nocb_gp_wq[rcu_seq_ctr(rnp->gp_seq) & 0x1]; +} + +static void rcu_init_one_nocb(struct rcu_node *rnp) +{ + init_swait_queue_head(&rnp->nocb_gp_wq[0]); + init_swait_queue_head(&rnp->nocb_gp_wq[1]); +} + +/* Is the specified CPU a no-CBs CPU? */ +bool rcu_is_nocb_cpu(int cpu) +{ + if (cpumask_available(rcu_nocb_mask)) + return cpumask_test_cpu(cpu, rcu_nocb_mask); + return false; +} + +/* + * Kick the leader kthread for this NOCB group. Caller holds ->nocb_lock + * and this function releases it. + */ +static void __wake_nocb_leader(struct rcu_data *rdp, bool force, + unsigned long flags) + __releases(rdp->nocb_lock) +{ + struct rcu_data *rdp_leader = rdp->nocb_leader; + + lockdep_assert_held(&rdp->nocb_lock); + if (!READ_ONCE(rdp_leader->nocb_kthread)) { + raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); + return; + } + if (rdp_leader->nocb_leader_sleep || force) { + /* Prior smp_mb__after_atomic() orders against prior enqueue. */ + WRITE_ONCE(rdp_leader->nocb_leader_sleep, false); + del_timer(&rdp->nocb_timer); + raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); + smp_mb(); /* ->nocb_leader_sleep before swake_up_one(). */ + swake_up_one(&rdp_leader->nocb_wq); + } else { + raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); + } +} + +/* + * Kick the leader kthread for this NOCB group, but caller has not + * acquired locks. + */ +static void wake_nocb_leader(struct rcu_data *rdp, bool force) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&rdp->nocb_lock, flags); + __wake_nocb_leader(rdp, force, flags); +} + +/* + * Arrange to wake the leader kthread for this NOCB group at some + * future time when it is safe to do so. + */ +static void wake_nocb_leader_defer(struct rcu_data *rdp, int waketype, + const char *reason) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&rdp->nocb_lock, flags); + if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_NOT) + mod_timer(&rdp->nocb_timer, jiffies + 1); + WRITE_ONCE(rdp->nocb_defer_wakeup, waketype); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, reason); + raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); +} + +/* + * Does the specified CPU need an RCU callback for the specified flavor + * of rcu_barrier()? + */ +static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + unsigned long ret; +#ifdef CONFIG_PROVE_RCU + struct rcu_head *rhp; +#endif /* #ifdef CONFIG_PROVE_RCU */ + + /* + * Check count of all no-CBs callbacks awaiting invocation. + * There needs to be a barrier before this function is called, + * but associated with a prior determination that no more + * callbacks would be posted. In the worst case, the first + * barrier in _rcu_barrier() suffices (but the caller cannot + * necessarily rely on this, not a substitute for the caller + * getting the concurrency design right!). There must also be + * a barrier between the following load an posting of a callback + * (if a callback is in fact needed). This is associated with an + * atomic_inc() in the caller. + */ + ret = atomic_long_read(&rdp->nocb_q_count); + +#ifdef CONFIG_PROVE_RCU + rhp = READ_ONCE(rdp->nocb_head); + if (!rhp) + rhp = READ_ONCE(rdp->nocb_gp_head); + if (!rhp) + rhp = READ_ONCE(rdp->nocb_follower_head); + + /* Having no rcuo kthread but CBs after scheduler starts is bad! */ + if (!READ_ONCE(rdp->nocb_kthread) && rhp && + rcu_scheduler_fully_active) { + /* RCU callback enqueued before CPU first came online??? */ + pr_err("RCU: Never-onlined no-CBs CPU %d has CB %p\n", + cpu, rhp->func); + WARN_ON_ONCE(1); + } +#endif /* #ifdef CONFIG_PROVE_RCU */ + + return !!ret; +} + +/* + * Enqueue the specified string of rcu_head structures onto the specified + * CPU's no-CBs lists. The CPU is specified by rdp, the head of the + * string by rhp, and the tail of the string by rhtp. The non-lazy/lazy + * counts are supplied by rhcount and rhcount_lazy. + * + * If warranted, also wake up the kthread servicing this CPUs queues. + */ +static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, + struct rcu_head *rhp, + struct rcu_head **rhtp, + int rhcount, int rhcount_lazy, + unsigned long flags) +{ + int len; + struct rcu_head **old_rhpp; + struct task_struct *t; + + /* Enqueue the callback on the nocb list and update counts. */ + atomic_long_add(rhcount, &rdp->nocb_q_count); + /* rcu_barrier() relies on ->nocb_q_count add before xchg. */ + old_rhpp = xchg(&rdp->nocb_tail, rhtp); + WRITE_ONCE(*old_rhpp, rhp); + atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy); + smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */ + + /* If we are not being polled and there is a kthread, awaken it ... */ + t = READ_ONCE(rdp->nocb_kthread); + if (rcu_nocb_poll || !t) { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WakeNotPoll")); + return; + } + len = atomic_long_read(&rdp->nocb_q_count); + if (old_rhpp == &rdp->nocb_head) { + if (!irqs_disabled_flags(flags)) { + /* ... if queue was empty ... */ + wake_nocb_leader(rdp, false); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WakeEmpty")); + } else { + wake_nocb_leader_defer(rdp, RCU_NOCB_WAKE, + TPS("WakeEmptyIsDeferred")); + } + rdp->qlen_last_fqs_check = 0; + } else if (len > rdp->qlen_last_fqs_check + qhimark) { + /* ... or if many callbacks queued. */ + if (!irqs_disabled_flags(flags)) { + wake_nocb_leader(rdp, true); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WakeOvf")); + } else { + wake_nocb_leader_defer(rdp, RCU_NOCB_WAKE_FORCE, + TPS("WakeOvfIsDeferred")); + } + rdp->qlen_last_fqs_check = LONG_MAX / 2; + } else { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot")); + } + return; +} + +/* + * This is a helper for __call_rcu(), which invokes this when the normal + * callback queue is inoperable. If this is not a no-CBs CPU, this + * function returns failure back to __call_rcu(), which can complain + * appropriately. + * + * Otherwise, this function queues the callback where the corresponding + * "rcuo" kthread can find it. + */ +static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, + bool lazy, unsigned long flags) +{ + + if (!rcu_is_nocb_cpu(rdp->cpu)) + return false; + __call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy, flags); + if (__is_kfree_rcu_offset((unsigned long)rhp->func)) + trace_rcu_kfree_callback(rdp->rsp->name, rhp, + (unsigned long)rhp->func, + -atomic_long_read(&rdp->nocb_q_count_lazy), + -atomic_long_read(&rdp->nocb_q_count)); + else + trace_rcu_callback(rdp->rsp->name, rhp, + -atomic_long_read(&rdp->nocb_q_count_lazy), + -atomic_long_read(&rdp->nocb_q_count)); + + /* + * If called from an extended quiescent state with interrupts + * disabled, invoke the RCU core in order to allow the idle-entry + * deferred-wakeup check to function. + */ + if (irqs_disabled_flags(flags) && + !rcu_is_watching() && + cpu_online(smp_processor_id())) + invoke_rcu_core(); + + return true; +} + +/* + * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is + * not a no-CBs CPU. + */ +static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp, + struct rcu_data *rdp, + unsigned long flags) +{ + lockdep_assert_irqs_disabled(); + if (!rcu_is_nocb_cpu(smp_processor_id())) + return false; /* Not NOCBs CPU, caller must migrate CBs. */ + __call_rcu_nocb_enqueue(my_rdp, rcu_segcblist_head(&rdp->cblist), + rcu_segcblist_tail(&rdp->cblist), + rcu_segcblist_n_cbs(&rdp->cblist), + rcu_segcblist_n_lazy_cbs(&rdp->cblist), flags); + rcu_segcblist_init(&rdp->cblist); + rcu_segcblist_disable(&rdp->cblist); + return true; +} + +/* + * If necessary, kick off a new grace period, and either way wait + * for a subsequent grace period to complete. + */ +static void rcu_nocb_wait_gp(struct rcu_data *rdp) +{ + unsigned long c; + bool d; + unsigned long flags; + bool needwake; + struct rcu_node *rnp = rdp->mynode; + + local_irq_save(flags); + c = rcu_seq_snap(&rdp->rsp->gp_seq); + if (!rdp->gpwrap && ULONG_CMP_GE(rdp->gp_seq_needed, c)) { + local_irq_restore(flags); + } else { + raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ + needwake = rcu_start_this_gp(rnp, rdp, c); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + if (needwake) + rcu_gp_kthread_wake(rdp->rsp); + } + + /* + * Wait for the grace period. Do so interruptibly to avoid messing + * up the load average. + */ + trace_rcu_this_gp(rnp, rdp, c, TPS("StartWait")); + for (;;) { + swait_event_interruptible_exclusive( + rnp->nocb_gp_wq[rcu_seq_ctr(c) & 0x1], + (d = rcu_seq_done(&rnp->gp_seq, c))); + if (likely(d)) + break; + WARN_ON(signal_pending(current)); + trace_rcu_this_gp(rnp, rdp, c, TPS("ResumeWait")); + } + trace_rcu_this_gp(rnp, rdp, c, TPS("EndWait")); + smp_mb(); /* Ensure that CB invocation happens after GP end. */ +} + +/* + * Leaders come here to wait for additional callbacks to show up. + * This function does not return until callbacks appear. + */ +static void nocb_leader_wait(struct rcu_data *my_rdp) +{ + bool firsttime = true; + unsigned long flags; + bool gotcbs; + struct rcu_data *rdp; + struct rcu_head **tail; + +wait_again: + + /* Wait for callbacks to appear. */ + if (!rcu_nocb_poll) { + trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, TPS("Sleep")); + swait_event_interruptible_exclusive(my_rdp->nocb_wq, + !READ_ONCE(my_rdp->nocb_leader_sleep)); + raw_spin_lock_irqsave(&my_rdp->nocb_lock, flags); + my_rdp->nocb_leader_sleep = true; + WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT); + del_timer(&my_rdp->nocb_timer); + raw_spin_unlock_irqrestore(&my_rdp->nocb_lock, flags); + } else if (firsttime) { + firsttime = false; /* Don't drown trace log with "Poll"! */ + trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, TPS("Poll")); + } + + /* + * Each pass through the following loop checks a follower for CBs. + * We are our own first follower. Any CBs found are moved to + * nocb_gp_head, where they await a grace period. + */ + gotcbs = false; + smp_mb(); /* wakeup and _sleep before ->nocb_head reads. */ + for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { + rdp->nocb_gp_head = READ_ONCE(rdp->nocb_head); + if (!rdp->nocb_gp_head) + continue; /* No CBs here, try next follower. */ + + /* Move callbacks to wait-for-GP list, which is empty. */ + WRITE_ONCE(rdp->nocb_head, NULL); + rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head); + gotcbs = true; + } + + /* No callbacks? Sleep a bit if polling, and go retry. */ + if (unlikely(!gotcbs)) { + WARN_ON(signal_pending(current)); + if (rcu_nocb_poll) { + schedule_timeout_interruptible(1); + } else { + trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, + TPS("WokeEmpty")); + } + goto wait_again; + } + + /* Wait for one grace period. */ + rcu_nocb_wait_gp(my_rdp); + + /* Each pass through the following loop wakes a follower, if needed. */ + for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { + if (!rcu_nocb_poll && + READ_ONCE(rdp->nocb_head) && + READ_ONCE(my_rdp->nocb_leader_sleep)) { + raw_spin_lock_irqsave(&my_rdp->nocb_lock, flags); + my_rdp->nocb_leader_sleep = false;/* No need to sleep.*/ + raw_spin_unlock_irqrestore(&my_rdp->nocb_lock, flags); + } + if (!rdp->nocb_gp_head) + continue; /* No CBs, so no need to wake follower. */ + + /* Append callbacks to follower's "done" list. */ + raw_spin_lock_irqsave(&rdp->nocb_lock, flags); + tail = rdp->nocb_follower_tail; + rdp->nocb_follower_tail = rdp->nocb_gp_tail; + *tail = rdp->nocb_gp_head; + raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); + if (rdp != my_rdp && tail == &rdp->nocb_follower_head) { + /* List was empty, so wake up the follower. */ + swake_up_one(&rdp->nocb_wq); + } + } + + /* If we (the leader) don't have CBs, go wait some more. */ + if (!my_rdp->nocb_follower_head) + goto wait_again; +} + +/* + * Followers come here to wait for additional callbacks to show up. + * This function does not return until callbacks appear. + */ +static void nocb_follower_wait(struct rcu_data *rdp) +{ + for (;;) { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("FollowerSleep")); + swait_event_interruptible_exclusive(rdp->nocb_wq, + READ_ONCE(rdp->nocb_follower_head)); + if (smp_load_acquire(&rdp->nocb_follower_head)) { + /* ^^^ Ensure CB invocation follows _head test. */ + return; + } + WARN_ON(signal_pending(current)); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WokeEmpty")); + } +} + +/* + * Per-rcu_data kthread, but only for no-CBs CPUs. Each kthread invokes + * callbacks queued by the corresponding no-CBs CPU, however, there is + * an optional leader-follower relationship so that the grace-period + * kthreads don't have to do quite so many wakeups. + */ +static int rcu_nocb_kthread(void *arg) +{ + int c, cl; + unsigned long flags; + struct rcu_head *list; + struct rcu_head *next; + struct rcu_head **tail; + struct rcu_data *rdp = arg; + + /* Each pass through this loop invokes one batch of callbacks */ + for (;;) { + /* Wait for callbacks. */ + if (rdp->nocb_leader == rdp) + nocb_leader_wait(rdp); + else + nocb_follower_wait(rdp); + + /* Pull the ready-to-invoke callbacks onto local list. */ + raw_spin_lock_irqsave(&rdp->nocb_lock, flags); + list = rdp->nocb_follower_head; + rdp->nocb_follower_head = NULL; + tail = rdp->nocb_follower_tail; + rdp->nocb_follower_tail = &rdp->nocb_follower_head; + raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); + BUG_ON(!list); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WokeNonEmpty")); + + /* Each pass through the following loop invokes a callback. */ + trace_rcu_batch_start(rdp->rsp->name, + atomic_long_read(&rdp->nocb_q_count_lazy), + atomic_long_read(&rdp->nocb_q_count), -1); + c = cl = 0; + while (list) { + next = list->next; + /* Wait for enqueuing to complete, if needed. */ + while (next == NULL && &list->next != tail) { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WaitQueue")); + schedule_timeout_interruptible(1); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WokeQueue")); + next = list->next; + } + debug_rcu_head_unqueue(list); + local_bh_disable(); + if (__rcu_reclaim(rdp->rsp->name, list)) + cl++; + c++; + local_bh_enable(); + cond_resched_tasks_rcu_qs(); + list = next; + } + trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); + smp_mb__before_atomic(); /* _add after CB invocation. */ + atomic_long_add(-c, &rdp->nocb_q_count); + atomic_long_add(-cl, &rdp->nocb_q_count_lazy); + } + return 0; +} + +/* Is a deferred wakeup of rcu_nocb_kthread() required? */ +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) +{ + return READ_ONCE(rdp->nocb_defer_wakeup); +} + +/* Do a deferred wakeup of rcu_nocb_kthread(). */ +static void do_nocb_deferred_wakeup_common(struct rcu_data *rdp) +{ + unsigned long flags; + int ndw; + + raw_spin_lock_irqsave(&rdp->nocb_lock, flags); + if (!rcu_nocb_need_deferred_wakeup(rdp)) { + raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); + return; + } + ndw = READ_ONCE(rdp->nocb_defer_wakeup); + WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT); + __wake_nocb_leader(rdp, ndw == RCU_NOCB_WAKE_FORCE, flags); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("DeferredWake")); +} + +/* Do a deferred wakeup of rcu_nocb_kthread() from a timer handler. */ +static void do_nocb_deferred_wakeup_timer(struct timer_list *t) +{ + struct rcu_data *rdp = from_timer(rdp, t, nocb_timer); + + do_nocb_deferred_wakeup_common(rdp); +} + +/* + * Do a deferred wakeup of rcu_nocb_kthread() from fastpath. + * This means we do an inexact common-case check. Note that if + * we miss, ->nocb_timer will eventually clean things up. + */ +static void do_nocb_deferred_wakeup(struct rcu_data *rdp) +{ + if (rcu_nocb_need_deferred_wakeup(rdp)) + do_nocb_deferred_wakeup_common(rdp); +} + +void __init rcu_init_nohz(void) +{ + int cpu; + bool need_rcu_nocb_mask = false; + struct rcu_state *rsp; + +#if defined(CONFIG_NO_HZ_FULL) + if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask)) + need_rcu_nocb_mask = true; +#endif /* #if defined(CONFIG_NO_HZ_FULL) */ + + if (!cpumask_available(rcu_nocb_mask) && need_rcu_nocb_mask) { + if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { + pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); + return; + } + } + if (!cpumask_available(rcu_nocb_mask)) + return; + +#if defined(CONFIG_NO_HZ_FULL) + if (tick_nohz_full_running) + cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); +#endif /* #if defined(CONFIG_NO_HZ_FULL) */ + + if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { + pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n"); + cpumask_and(rcu_nocb_mask, cpu_possible_mask, + rcu_nocb_mask); + } + if (cpumask_empty(rcu_nocb_mask)) + pr_info("\tOffload RCU callbacks from CPUs: (none).\n"); + else + pr_info("\tOffload RCU callbacks from CPUs: %*pbl.\n", + cpumask_pr_args(rcu_nocb_mask)); + if (rcu_nocb_poll) + pr_info("\tPoll for callbacks from no-CBs CPUs.\n"); + + for_each_rcu_flavor(rsp) { + for_each_cpu(cpu, rcu_nocb_mask) + init_nocb_callback_list(per_cpu_ptr(rsp->rda, cpu)); + rcu_organize_nocb_kthreads(rsp); + } +} + +/* Initialize per-rcu_data variables for no-CBs CPUs. */ +static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) +{ + rdp->nocb_tail = &rdp->nocb_head; + init_swait_queue_head(&rdp->nocb_wq); + rdp->nocb_follower_tail = &rdp->nocb_follower_head; + raw_spin_lock_init(&rdp->nocb_lock); + timer_setup(&rdp->nocb_timer, do_nocb_deferred_wakeup_timer, 0); +} + +/* + * If the specified CPU is a no-CBs CPU that does not already have its + * rcuo kthread for the specified RCU flavor, spawn it. If the CPUs are + * brought online out of order, this can require re-organizing the + * leader-follower relationships. + */ +static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu) +{ + struct rcu_data *rdp; + struct rcu_data *rdp_last; + struct rcu_data *rdp_old_leader; + struct rcu_data *rdp_spawn = per_cpu_ptr(rsp->rda, cpu); + struct task_struct *t; + + /* + * If this isn't a no-CBs CPU or if it already has an rcuo kthread, + * then nothing to do. + */ + if (!rcu_is_nocb_cpu(cpu) || rdp_spawn->nocb_kthread) + return; + + /* If we didn't spawn the leader first, reorganize! */ + rdp_old_leader = rdp_spawn->nocb_leader; + if (rdp_old_leader != rdp_spawn && !rdp_old_leader->nocb_kthread) { + rdp_last = NULL; + rdp = rdp_old_leader; + do { + rdp->nocb_leader = rdp_spawn; + if (rdp_last && rdp != rdp_spawn) + rdp_last->nocb_next_follower = rdp; + if (rdp == rdp_spawn) { + rdp = rdp->nocb_next_follower; + } else { + rdp_last = rdp; + rdp = rdp->nocb_next_follower; + rdp_last->nocb_next_follower = NULL; + } + } while (rdp); + rdp_spawn->nocb_next_follower = rdp_old_leader; + } + + /* Spawn the kthread for this CPU and RCU flavor. */ + t = kthread_run(rcu_nocb_kthread, rdp_spawn, + "rcuo%c/%d", rsp->abbr, cpu); + BUG_ON(IS_ERR(t)); + WRITE_ONCE(rdp_spawn->nocb_kthread, t); +} + +/* + * If the specified CPU is a no-CBs CPU that does not already have its + * rcuo kthreads, spawn them. + */ +static void rcu_spawn_all_nocb_kthreads(int cpu) +{ + struct rcu_state *rsp; + + if (rcu_scheduler_fully_active) + for_each_rcu_flavor(rsp) + rcu_spawn_one_nocb_kthread(rsp, cpu); +} + +/* + * Once the scheduler is running, spawn rcuo kthreads for all online + * no-CBs CPUs. This assumes that the early_initcall()s happen before + * non-boot CPUs come online -- if this changes, we will need to add + * some mutual exclusion. + */ +static void __init rcu_spawn_nocb_kthreads(void) +{ + int cpu; + + for_each_online_cpu(cpu) + rcu_spawn_all_nocb_kthreads(cpu); +} + +/* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids). */ +static int rcu_nocb_leader_stride = -1; +module_param(rcu_nocb_leader_stride, int, 0444); + +/* + * Initialize leader-follower relationships for all no-CBs CPU. + */ +static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) +{ + int cpu; + int ls = rcu_nocb_leader_stride; + int nl = 0; /* Next leader. */ + struct rcu_data *rdp; + struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ + struct rcu_data *rdp_prev = NULL; + + if (!cpumask_available(rcu_nocb_mask)) + return; + if (ls == -1) { + ls = int_sqrt(nr_cpu_ids); + rcu_nocb_leader_stride = ls; + } + + /* + * Each pass through this loop sets up one rcu_data structure. + * Should the corresponding CPU come online in the future, then + * we will spawn the needed set of rcu_nocb_kthread() kthreads. + */ + for_each_cpu(cpu, rcu_nocb_mask) { + rdp = per_cpu_ptr(rsp->rda, cpu); + if (rdp->cpu >= nl) { + /* New leader, set up for followers & next leader. */ + nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls; + rdp->nocb_leader = rdp; + rdp_leader = rdp; + } else { + /* Another follower, link to previous leader. */ + rdp->nocb_leader = rdp_leader; + rdp_prev->nocb_next_follower = rdp; + } + rdp_prev = rdp; + } +} + +/* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ +static bool init_nocb_callback_list(struct rcu_data *rdp) +{ + if (!rcu_is_nocb_cpu(rdp->cpu)) + return false; + + /* If there are early-boot callbacks, move them to nocb lists. */ + if (!rcu_segcblist_empty(&rdp->cblist)) { + rdp->nocb_head = rcu_segcblist_head(&rdp->cblist); + rdp->nocb_tail = rcu_segcblist_tail(&rdp->cblist); + atomic_long_set(&rdp->nocb_q_count, + rcu_segcblist_n_cbs(&rdp->cblist)); + atomic_long_set(&rdp->nocb_q_count_lazy, + rcu_segcblist_n_lazy_cbs(&rdp->cblist)); + rcu_segcblist_init(&rdp->cblist); + } + rcu_segcblist_disable(&rdp->cblist); + return true; +} + +#else /* #ifdef CONFIG_RCU_NOCB_CPU */ + +static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) +{ + WARN_ON_ONCE(1); /* Should be dead code. */ + return false; +} + +static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq) +{ +} + +static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp) +{ + return NULL; +} + +static void rcu_init_one_nocb(struct rcu_node *rnp) +{ +} + +static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, + bool lazy, unsigned long flags) +{ + return false; +} + +static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp, + struct rcu_data *rdp, + unsigned long flags) +{ + return false; +} + +static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) +{ +} + +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) +{ + return false; +} + +static void do_nocb_deferred_wakeup(struct rcu_data *rdp) +{ +} + +static void rcu_spawn_all_nocb_kthreads(int cpu) +{ +} + +static void __init rcu_spawn_nocb_kthreads(void) +{ +} + +static bool init_nocb_callback_list(struct rcu_data *rdp) +{ + return false; +} + +#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ + +/* + * Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the + * grace-period kthread will do force_quiescent_state() processing? + * The idea is to avoid waking up RCU core processing on such a + * CPU unless the grace period has extended for too long. + * + * This code relies on the fact that all NO_HZ_FULL CPUs are also + * CONFIG_RCU_NOCB_CPU CPUs. + */ +static bool rcu_nohz_full_cpu(struct rcu_state *rsp) +{ +#ifdef CONFIG_NO_HZ_FULL + if (tick_nohz_full_cpu(smp_processor_id()) && + (!rcu_gp_in_progress(rsp) || + ULONG_CMP_LT(jiffies, READ_ONCE(rsp->gp_start) + HZ))) + return true; +#endif /* #ifdef CONFIG_NO_HZ_FULL */ + return false; +} + +/* + * Bind the RCU grace-period kthreads to the housekeeping CPU. + */ +static void rcu_bind_gp_kthread(void) +{ + if (!tick_nohz_full_enabled()) + return; + housekeeping_affine(current, HK_FLAG_RCU); +} + +/* Record the current task on dyntick-idle entry. */ +static void rcu_dynticks_task_enter(void) +{ +#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) + WRITE_ONCE(current->rcu_tasks_idle_cpu, smp_processor_id()); +#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ +} + +/* Record no current task on dyntick-idle exit. */ +static void rcu_dynticks_task_exit(void) +{ +#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) + WRITE_ONCE(current->rcu_tasks_idle_cpu, -1); +#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ +} diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c new file mode 100644 index 000000000..81688a133 --- /dev/null +++ b/kernel/rcu/update.c @@ -0,0 +1,977 @@ +/* + * Read-Copy Update mechanism for mutual exclusion + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2001 + * + * Authors: Dipankar Sarma <dipankar@in.ibm.com> + * Manfred Spraul <manfred@colorfullife.com> + * + * Based on the original work by Paul McKenney <paulmck@us.ibm.com> + * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. + * Papers: + * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf + * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) + * + * For detailed explanation of Read-Copy Update mechanism see - + * http://lse.sourceforge.net/locking/rcupdate.html + * + */ +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/spinlock.h> +#include <linux/smp.h> +#include <linux/interrupt.h> +#include <linux/sched/signal.h> +#include <linux/sched/debug.h> +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/percpu.h> +#include <linux/notifier.h> +#include <linux/cpu.h> +#include <linux/mutex.h> +#include <linux/export.h> +#include <linux/hardirq.h> +#include <linux/delay.h> +#include <linux/moduleparam.h> +#include <linux/kthread.h> +#include <linux/tick.h> +#include <linux/rcupdate_wait.h> +#include <linux/sched/isolation.h> +#include <linux/kprobes.h> + +#define CREATE_TRACE_POINTS + +#include "rcu.h" + +#ifdef MODULE_PARAM_PREFIX +#undef MODULE_PARAM_PREFIX +#endif +#define MODULE_PARAM_PREFIX "rcupdate." + +#ifndef CONFIG_TINY_RCU +extern int rcu_expedited; /* from sysctl */ +module_param(rcu_expedited, int, 0); +extern int rcu_normal; /* from sysctl */ +module_param(rcu_normal, int, 0); +static int rcu_normal_after_boot; +module_param(rcu_normal_after_boot, int, 0); +#endif /* #ifndef CONFIG_TINY_RCU */ + +#ifdef CONFIG_DEBUG_LOCK_ALLOC +/** + * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? + * + * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an + * RCU-sched read-side critical section. In absence of + * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side + * critical section unless it can prove otherwise. Note that disabling + * of preemption (including disabling irqs) counts as an RCU-sched + * read-side critical section. This is useful for debug checks in functions + * that required that they be called within an RCU-sched read-side + * critical section. + * + * Check debug_lockdep_rcu_enabled() to prevent false positives during boot + * and while lockdep is disabled. + * + * Note that if the CPU is in the idle loop from an RCU point of + * view (ie: that we are in the section between rcu_idle_enter() and + * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU + * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs + * that are in such a section, considering these as in extended quiescent + * state, so such a CPU is effectively never in an RCU read-side critical + * section regardless of what RCU primitives it invokes. This state of + * affairs is required --- we need to keep an RCU-free window in idle + * where the CPU may possibly enter into low power mode. This way we can + * notice an extended quiescent state to other CPUs that started a grace + * period. Otherwise we would delay any grace period as long as we run in + * the idle task. + * + * Similarly, we avoid claiming an SRCU read lock held if the current + * CPU is offline. + */ +int rcu_read_lock_sched_held(void) +{ + int lockdep_opinion = 0; + + if (!debug_lockdep_rcu_enabled()) + return 1; + if (!rcu_is_watching()) + return 0; + if (!rcu_lockdep_current_cpu_online()) + return 0; + if (debug_locks) + lockdep_opinion = lock_is_held(&rcu_sched_lock_map); + return lockdep_opinion || !preemptible(); +} +EXPORT_SYMBOL(rcu_read_lock_sched_held); +#endif + +#ifndef CONFIG_TINY_RCU + +/* + * Should expedited grace-period primitives always fall back to their + * non-expedited counterparts? Intended for use within RCU. Note + * that if the user specifies both rcu_expedited and rcu_normal, then + * rcu_normal wins. (Except during the time period during boot from + * when the first task is spawned until the rcu_set_runtime_mode() + * core_initcall() is invoked, at which point everything is expedited.) + */ +bool rcu_gp_is_normal(void) +{ + return READ_ONCE(rcu_normal) && + rcu_scheduler_active != RCU_SCHEDULER_INIT; +} +EXPORT_SYMBOL_GPL(rcu_gp_is_normal); + +static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1); + +/* + * Should normal grace-period primitives be expedited? Intended for + * use within RCU. Note that this function takes the rcu_expedited + * sysfs/boot variable and rcu_scheduler_active into account as well + * as the rcu_expedite_gp() nesting. So looping on rcu_unexpedite_gp() + * until rcu_gp_is_expedited() returns false is a -really- bad idea. + */ +bool rcu_gp_is_expedited(void) +{ + return rcu_expedited || atomic_read(&rcu_expedited_nesting) || + rcu_scheduler_active == RCU_SCHEDULER_INIT; +} +EXPORT_SYMBOL_GPL(rcu_gp_is_expedited); + +/** + * rcu_expedite_gp - Expedite future RCU grace periods + * + * After a call to this function, future calls to synchronize_rcu() and + * friends act as the corresponding synchronize_rcu_expedited() function + * had instead been called. + */ +void rcu_expedite_gp(void) +{ + atomic_inc(&rcu_expedited_nesting); +} +EXPORT_SYMBOL_GPL(rcu_expedite_gp); + +/** + * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation + * + * Undo a prior call to rcu_expedite_gp(). If all prior calls to + * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(), + * and if the rcu_expedited sysfs/boot parameter is not set, then all + * subsequent calls to synchronize_rcu() and friends will return to + * their normal non-expedited behavior. + */ +void rcu_unexpedite_gp(void) +{ + atomic_dec(&rcu_expedited_nesting); +} +EXPORT_SYMBOL_GPL(rcu_unexpedite_gp); + +/* + * Inform RCU of the end of the in-kernel boot sequence. + */ +void rcu_end_inkernel_boot(void) +{ + rcu_unexpedite_gp(); + if (rcu_normal_after_boot) + WRITE_ONCE(rcu_normal, 1); +} + +#endif /* #ifndef CONFIG_TINY_RCU */ + +/* + * Test each non-SRCU synchronous grace-period wait API. This is + * useful just after a change in mode for these primitives, and + * during early boot. + */ +void rcu_test_sync_prims(void) +{ + if (!IS_ENABLED(CONFIG_PROVE_RCU)) + return; + synchronize_rcu(); + synchronize_rcu_bh(); + synchronize_sched(); + synchronize_rcu_expedited(); + synchronize_rcu_bh_expedited(); + synchronize_sched_expedited(); +} + +#if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) + +/* + * Switch to run-time mode once RCU has fully initialized. + */ +static int __init rcu_set_runtime_mode(void) +{ + rcu_test_sync_prims(); + rcu_scheduler_active = RCU_SCHEDULER_RUNNING; + rcu_test_sync_prims(); + return 0; +} +core_initcall(rcu_set_runtime_mode); + +#endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */ + +#ifdef CONFIG_DEBUG_LOCK_ALLOC +static struct lock_class_key rcu_lock_key; +struct lockdep_map rcu_lock_map = + STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); +EXPORT_SYMBOL_GPL(rcu_lock_map); + +static struct lock_class_key rcu_bh_lock_key; +struct lockdep_map rcu_bh_lock_map = + STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key); +EXPORT_SYMBOL_GPL(rcu_bh_lock_map); + +static struct lock_class_key rcu_sched_lock_key; +struct lockdep_map rcu_sched_lock_map = + STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key); +EXPORT_SYMBOL_GPL(rcu_sched_lock_map); + +static struct lock_class_key rcu_callback_key; +struct lockdep_map rcu_callback_map = + STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key); +EXPORT_SYMBOL_GPL(rcu_callback_map); + +int notrace debug_lockdep_rcu_enabled(void) +{ + return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && debug_locks && + current->lockdep_recursion == 0; +} +EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); +NOKPROBE_SYMBOL(debug_lockdep_rcu_enabled); + +/** + * rcu_read_lock_held() - might we be in RCU read-side critical section? + * + * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU + * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, + * this assumes we are in an RCU read-side critical section unless it can + * prove otherwise. This is useful for debug checks in functions that + * require that they be called within an RCU read-side critical section. + * + * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot + * and while lockdep is disabled. + * + * Note that rcu_read_lock() and the matching rcu_read_unlock() must + * occur in the same context, for example, it is illegal to invoke + * rcu_read_unlock() in process context if the matching rcu_read_lock() + * was invoked from within an irq handler. + * + * Note that rcu_read_lock() is disallowed if the CPU is either idle or + * offline from an RCU perspective, so check for those as well. + */ +int rcu_read_lock_held(void) +{ + if (!debug_lockdep_rcu_enabled()) + return 1; + if (!rcu_is_watching()) + return 0; + if (!rcu_lockdep_current_cpu_online()) + return 0; + return lock_is_held(&rcu_lock_map); +} +EXPORT_SYMBOL_GPL(rcu_read_lock_held); + +/** + * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? + * + * Check for bottom half being disabled, which covers both the + * CONFIG_PROVE_RCU and not cases. Note that if someone uses + * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) + * will show the situation. This is useful for debug checks in functions + * that require that they be called within an RCU read-side critical + * section. + * + * Check debug_lockdep_rcu_enabled() to prevent false positives during boot. + * + * Note that rcu_read_lock() is disallowed if the CPU is either idle or + * offline from an RCU perspective, so check for those as well. + */ +int rcu_read_lock_bh_held(void) +{ + if (!debug_lockdep_rcu_enabled()) + return 1; + if (!rcu_is_watching()) + return 0; + if (!rcu_lockdep_current_cpu_online()) + return 0; + return in_softirq() || irqs_disabled(); +} +EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); + +#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +/** + * wakeme_after_rcu() - Callback function to awaken a task after grace period + * @head: Pointer to rcu_head member within rcu_synchronize structure + * + * Awaken the corresponding task now that a grace period has elapsed. + */ +void wakeme_after_rcu(struct rcu_head *head) +{ + struct rcu_synchronize *rcu; + + rcu = container_of(head, struct rcu_synchronize, head); + complete(&rcu->completion); +} +EXPORT_SYMBOL_GPL(wakeme_after_rcu); + +void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, + struct rcu_synchronize *rs_array) +{ + int i; + int j; + + /* Initialize and register callbacks for each flavor specified. */ + for (i = 0; i < n; i++) { + if (checktiny && + (crcu_array[i] == call_rcu || + crcu_array[i] == call_rcu_bh)) { + might_sleep(); + continue; + } + init_rcu_head_on_stack(&rs_array[i].head); + init_completion(&rs_array[i].completion); + for (j = 0; j < i; j++) + if (crcu_array[j] == crcu_array[i]) + break; + if (j == i) + (crcu_array[i])(&rs_array[i].head, wakeme_after_rcu); + } + + /* Wait for all callbacks to be invoked. */ + for (i = 0; i < n; i++) { + if (checktiny && + (crcu_array[i] == call_rcu || + crcu_array[i] == call_rcu_bh)) + continue; + for (j = 0; j < i; j++) + if (crcu_array[j] == crcu_array[i]) + break; + if (j == i) + wait_for_completion(&rs_array[i].completion); + destroy_rcu_head_on_stack(&rs_array[i].head); + } +} +EXPORT_SYMBOL_GPL(__wait_rcu_gp); + +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD +void init_rcu_head(struct rcu_head *head) +{ + debug_object_init(head, &rcuhead_debug_descr); +} +EXPORT_SYMBOL_GPL(init_rcu_head); + +void destroy_rcu_head(struct rcu_head *head) +{ + debug_object_free(head, &rcuhead_debug_descr); +} +EXPORT_SYMBOL_GPL(destroy_rcu_head); + +static bool rcuhead_is_static_object(void *addr) +{ + return true; +} + +/** + * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects + * @head: pointer to rcu_head structure to be initialized + * + * This function informs debugobjects of a new rcu_head structure that + * has been allocated as an auto variable on the stack. This function + * is not required for rcu_head structures that are statically defined or + * that are dynamically allocated on the heap. This function has no + * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. + */ +void init_rcu_head_on_stack(struct rcu_head *head) +{ + debug_object_init_on_stack(head, &rcuhead_debug_descr); +} +EXPORT_SYMBOL_GPL(init_rcu_head_on_stack); + +/** + * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects + * @head: pointer to rcu_head structure to be initialized + * + * This function informs debugobjects that an on-stack rcu_head structure + * is about to go out of scope. As with init_rcu_head_on_stack(), this + * function is not required for rcu_head structures that are statically + * defined or that are dynamically allocated on the heap. Also as with + * init_rcu_head_on_stack(), this function has no effect for + * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. + */ +void destroy_rcu_head_on_stack(struct rcu_head *head) +{ + debug_object_free(head, &rcuhead_debug_descr); +} +EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack); + +struct debug_obj_descr rcuhead_debug_descr = { + .name = "rcu_head", + .is_static_object = rcuhead_is_static_object, +}; +EXPORT_SYMBOL_GPL(rcuhead_debug_descr); +#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ + +#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE) +void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, unsigned long c) +{ + trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c); +} +EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read); +#else +#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ + do { } while (0) +#endif + +#ifdef CONFIG_RCU_STALL_COMMON + +#ifdef CONFIG_PROVE_RCU +#define RCU_STALL_DELAY_DELTA (5 * HZ) +#else +#define RCU_STALL_DELAY_DELTA 0 +#endif + +int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ +EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress); +static int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; + +module_param(rcu_cpu_stall_suppress, int, 0644); +module_param(rcu_cpu_stall_timeout, int, 0644); + +int rcu_jiffies_till_stall_check(void) +{ + int till_stall_check = READ_ONCE(rcu_cpu_stall_timeout); + + /* + * Limit check must be consistent with the Kconfig limits + * for CONFIG_RCU_CPU_STALL_TIMEOUT. + */ + if (till_stall_check < 3) { + WRITE_ONCE(rcu_cpu_stall_timeout, 3); + till_stall_check = 3; + } else if (till_stall_check > 300) { + WRITE_ONCE(rcu_cpu_stall_timeout, 300); + till_stall_check = 300; + } + return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; +} + +void rcu_sysrq_start(void) +{ + if (!rcu_cpu_stall_suppress) + rcu_cpu_stall_suppress = 2; +} + +void rcu_sysrq_end(void) +{ + if (rcu_cpu_stall_suppress == 2) + rcu_cpu_stall_suppress = 0; +} + +static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) +{ + rcu_cpu_stall_suppress = 1; + return NOTIFY_DONE; +} + +static struct notifier_block rcu_panic_block = { + .notifier_call = rcu_panic, +}; + +static int __init check_cpu_stall_init(void) +{ + atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); + return 0; +} +early_initcall(check_cpu_stall_init); + +#endif /* #ifdef CONFIG_RCU_STALL_COMMON */ + +#ifdef CONFIG_TASKS_RCU + +/* + * Simple variant of RCU whose quiescent states are voluntary context + * switch, cond_resched_rcu_qs(), user-space execution, and idle. + * As such, grace periods can take one good long time. There are no + * read-side primitives similar to rcu_read_lock() and rcu_read_unlock() + * because this implementation is intended to get the system into a safe + * state for some of the manipulations involved in tracing and the like. + * Finally, this implementation does not support high call_rcu_tasks() + * rates from multiple CPUs. If this is required, per-CPU callback lists + * will be needed. + */ + +/* Global list of callbacks and associated lock. */ +static struct rcu_head *rcu_tasks_cbs_head; +static struct rcu_head **rcu_tasks_cbs_tail = &rcu_tasks_cbs_head; +static DECLARE_WAIT_QUEUE_HEAD(rcu_tasks_cbs_wq); +static DEFINE_RAW_SPINLOCK(rcu_tasks_cbs_lock); + +/* Track exiting tasks in order to allow them to be waited for. */ +DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu); + +/* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */ +#define RCU_TASK_STALL_TIMEOUT (HZ * 60 * 10) +static int rcu_task_stall_timeout __read_mostly = RCU_TASK_STALL_TIMEOUT; +module_param(rcu_task_stall_timeout, int, 0644); + +static struct task_struct *rcu_tasks_kthread_ptr; + +/** + * call_rcu_tasks() - Queue an RCU for invocation task-based grace period + * @rhp: structure to be used for queueing the RCU updates. + * @func: actual callback function to be invoked after the grace period + * + * The callback function will be invoked some time after a full grace + * period elapses, in other words after all currently executing RCU + * read-side critical sections have completed. call_rcu_tasks() assumes + * that the read-side critical sections end at a voluntary context + * switch (not a preemption!), cond_resched_rcu_qs(), entry into idle, + * or transition to usermode execution. As such, there are no read-side + * primitives analogous to rcu_read_lock() and rcu_read_unlock() because + * this primitive is intended to determine that all tasks have passed + * through a safe state, not so much for data-strcuture synchronization. + * + * See the description of call_rcu() for more detailed information on + * memory ordering guarantees. + */ +void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func) +{ + unsigned long flags; + bool needwake; + + rhp->next = NULL; + rhp->func = func; + raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags); + needwake = !rcu_tasks_cbs_head; + *rcu_tasks_cbs_tail = rhp; + rcu_tasks_cbs_tail = &rhp->next; + raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags); + /* We can't create the thread unless interrupts are enabled. */ + if (needwake && READ_ONCE(rcu_tasks_kthread_ptr)) + wake_up(&rcu_tasks_cbs_wq); +} +EXPORT_SYMBOL_GPL(call_rcu_tasks); + +/** + * synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed. + * + * Control will return to the caller some time after a full rcu-tasks + * grace period has elapsed, in other words after all currently + * executing rcu-tasks read-side critical sections have elapsed. These + * read-side critical sections are delimited by calls to schedule(), + * cond_resched_tasks_rcu_qs(), idle execution, userspace execution, calls + * to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched(). + * + * This is a very specialized primitive, intended only for a few uses in + * tracing and other situations requiring manipulation of function + * preambles and profiling hooks. The synchronize_rcu_tasks() function + * is not (yet) intended for heavy use from multiple CPUs. + * + * Note that this guarantee implies further memory-ordering guarantees. + * On systems with more than one CPU, when synchronize_rcu_tasks() returns, + * each CPU is guaranteed to have executed a full memory barrier since the + * end of its last RCU-tasks read-side critical section whose beginning + * preceded the call to synchronize_rcu_tasks(). In addition, each CPU + * having an RCU-tasks read-side critical section that extends beyond + * the return from synchronize_rcu_tasks() is guaranteed to have executed + * a full memory barrier after the beginning of synchronize_rcu_tasks() + * and before the beginning of that RCU-tasks read-side critical section. + * Note that these guarantees include CPUs that are offline, idle, or + * executing in user mode, as well as CPUs that are executing in the kernel. + * + * Furthermore, if CPU A invoked synchronize_rcu_tasks(), which returned + * to its caller on CPU B, then both CPU A and CPU B are guaranteed + * to have executed a full memory barrier during the execution of + * synchronize_rcu_tasks() -- even if CPU A and CPU B are the same CPU + * (but again only if the system has more than one CPU). + */ +void synchronize_rcu_tasks(void) +{ + /* Complain if the scheduler has not started. */ + RCU_LOCKDEP_WARN(rcu_scheduler_active == RCU_SCHEDULER_INACTIVE, + "synchronize_rcu_tasks called too soon"); + + /* Wait for the grace period. */ + wait_rcu_gp(call_rcu_tasks); +} +EXPORT_SYMBOL_GPL(synchronize_rcu_tasks); + +/** + * rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks. + * + * Although the current implementation is guaranteed to wait, it is not + * obligated to, for example, if there are no pending callbacks. + */ +void rcu_barrier_tasks(void) +{ + /* There is only one callback queue, so this is easy. ;-) */ + synchronize_rcu_tasks(); +} +EXPORT_SYMBOL_GPL(rcu_barrier_tasks); + +/* See if tasks are still holding out, complain if so. */ +static void check_holdout_task(struct task_struct *t, + bool needreport, bool *firstreport) +{ + int cpu; + + if (!READ_ONCE(t->rcu_tasks_holdout) || + t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) || + !READ_ONCE(t->on_rq) || + (IS_ENABLED(CONFIG_NO_HZ_FULL) && + !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) { + WRITE_ONCE(t->rcu_tasks_holdout, false); + list_del_init(&t->rcu_tasks_holdout_list); + put_task_struct(t); + return; + } + rcu_request_urgent_qs_task(t); + if (!needreport) + return; + if (*firstreport) { + pr_err("INFO: rcu_tasks detected stalls on tasks:\n"); + *firstreport = false; + } + cpu = task_cpu(t); + pr_alert("%p: %c%c nvcsw: %lu/%lu holdout: %d idle_cpu: %d/%d\n", + t, ".I"[is_idle_task(t)], + "N."[cpu < 0 || !tick_nohz_full_cpu(cpu)], + t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout, + t->rcu_tasks_idle_cpu, cpu); + sched_show_task(t); +} + +/* RCU-tasks kthread that detects grace periods and invokes callbacks. */ +static int __noreturn rcu_tasks_kthread(void *arg) +{ + unsigned long flags; + struct task_struct *g, *t; + unsigned long lastreport; + struct rcu_head *list; + struct rcu_head *next; + LIST_HEAD(rcu_tasks_holdouts); + int fract; + + /* Run on housekeeping CPUs by default. Sysadm can move if desired. */ + housekeeping_affine(current, HK_FLAG_RCU); + + /* + * Each pass through the following loop makes one check for + * newly arrived callbacks, and, if there are some, waits for + * one RCU-tasks grace period and then invokes the callbacks. + * This loop is terminated by the system going down. ;-) + */ + for (;;) { + + /* Pick up any new callbacks. */ + raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags); + list = rcu_tasks_cbs_head; + rcu_tasks_cbs_head = NULL; + rcu_tasks_cbs_tail = &rcu_tasks_cbs_head; + raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags); + + /* If there were none, wait a bit and start over. */ + if (!list) { + wait_event_interruptible(rcu_tasks_cbs_wq, + rcu_tasks_cbs_head); + if (!rcu_tasks_cbs_head) { + WARN_ON(signal_pending(current)); + schedule_timeout_interruptible(HZ/10); + } + continue; + } + + /* + * Wait for all pre-existing t->on_rq and t->nvcsw + * transitions to complete. Invoking synchronize_sched() + * suffices because all these transitions occur with + * interrupts disabled. Without this synchronize_sched(), + * a read-side critical section that started before the + * grace period might be incorrectly seen as having started + * after the grace period. + * + * This synchronize_sched() also dispenses with the + * need for a memory barrier on the first store to + * ->rcu_tasks_holdout, as it forces the store to happen + * after the beginning of the grace period. + */ + synchronize_sched(); + + /* + * There were callbacks, so we need to wait for an + * RCU-tasks grace period. Start off by scanning + * the task list for tasks that are not already + * voluntarily blocked. Mark these tasks and make + * a list of them in rcu_tasks_holdouts. + */ + rcu_read_lock(); + for_each_process_thread(g, t) { + if (t != current && READ_ONCE(t->on_rq) && + !is_idle_task(t)) { + get_task_struct(t); + t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw); + WRITE_ONCE(t->rcu_tasks_holdout, true); + list_add(&t->rcu_tasks_holdout_list, + &rcu_tasks_holdouts); + } + } + rcu_read_unlock(); + + /* + * Wait for tasks that are in the process of exiting. + * This does only part of the job, ensuring that all + * tasks that were previously exiting reach the point + * where they have disabled preemption, allowing the + * later synchronize_sched() to finish the job. + */ + synchronize_srcu(&tasks_rcu_exit_srcu); + + /* + * Each pass through the following loop scans the list + * of holdout tasks, removing any that are no longer + * holdouts. When the list is empty, we are done. + */ + lastreport = jiffies; + + /* Start off with HZ/10 wait and slowly back off to 1 HZ wait*/ + fract = 10; + + for (;;) { + bool firstreport; + bool needreport; + int rtst; + struct task_struct *t1; + + if (list_empty(&rcu_tasks_holdouts)) + break; + + /* Slowly back off waiting for holdouts */ + schedule_timeout_interruptible(HZ/fract); + + if (fract > 1) + fract--; + + rtst = READ_ONCE(rcu_task_stall_timeout); + needreport = rtst > 0 && + time_after(jiffies, lastreport + rtst); + if (needreport) + lastreport = jiffies; + firstreport = true; + WARN_ON(signal_pending(current)); + list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts, + rcu_tasks_holdout_list) { + check_holdout_task(t, needreport, &firstreport); + cond_resched(); + } + } + + /* + * Because ->on_rq and ->nvcsw are not guaranteed + * to have a full memory barriers prior to them in the + * schedule() path, memory reordering on other CPUs could + * cause their RCU-tasks read-side critical sections to + * extend past the end of the grace period. However, + * because these ->nvcsw updates are carried out with + * interrupts disabled, we can use synchronize_sched() + * to force the needed ordering on all such CPUs. + * + * This synchronize_sched() also confines all + * ->rcu_tasks_holdout accesses to be within the grace + * period, avoiding the need for memory barriers for + * ->rcu_tasks_holdout accesses. + * + * In addition, this synchronize_sched() waits for exiting + * tasks to complete their final preempt_disable() region + * of execution, cleaning up after the synchronize_srcu() + * above. + */ + synchronize_sched(); + + /* Invoke the callbacks. */ + while (list) { + next = list->next; + local_bh_disable(); + list->func(list); + local_bh_enable(); + list = next; + cond_resched(); + } + /* Paranoid sleep to keep this from entering a tight loop */ + schedule_timeout_uninterruptible(HZ/10); + } +} + +/* Spawn rcu_tasks_kthread() at core_initcall() time. */ +static int __init rcu_spawn_tasks_kthread(void) +{ + struct task_struct *t; + + t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread"); + BUG_ON(IS_ERR(t)); + smp_mb(); /* Ensure others see full kthread. */ + WRITE_ONCE(rcu_tasks_kthread_ptr, t); + return 0; +} +core_initcall(rcu_spawn_tasks_kthread); + +/* Do the srcu_read_lock() for the above synchronize_srcu(). */ +void exit_tasks_rcu_start(void) +{ + preempt_disable(); + current->rcu_tasks_idx = __srcu_read_lock(&tasks_rcu_exit_srcu); + preempt_enable(); +} + +/* Do the srcu_read_unlock() for the above synchronize_srcu(). */ +void exit_tasks_rcu_finish(void) +{ + preempt_disable(); + __srcu_read_unlock(&tasks_rcu_exit_srcu, current->rcu_tasks_idx); + preempt_enable(); +} + +#endif /* #ifdef CONFIG_TASKS_RCU */ + +#ifndef CONFIG_TINY_RCU + +/* + * Print any non-default Tasks RCU settings. + */ +static void __init rcu_tasks_bootup_oddness(void) +{ +#ifdef CONFIG_TASKS_RCU + if (rcu_task_stall_timeout != RCU_TASK_STALL_TIMEOUT) + pr_info("\tTasks-RCU CPU stall warnings timeout set to %d (rcu_task_stall_timeout).\n", rcu_task_stall_timeout); + else + pr_info("\tTasks RCU enabled.\n"); +#endif /* #ifdef CONFIG_TASKS_RCU */ +} + +#endif /* #ifndef CONFIG_TINY_RCU */ + +#ifdef CONFIG_PROVE_RCU + +/* + * Early boot self test parameters, one for each flavor + */ +static bool rcu_self_test; +static bool rcu_self_test_bh; +static bool rcu_self_test_sched; + +module_param(rcu_self_test, bool, 0444); +module_param(rcu_self_test_bh, bool, 0444); +module_param(rcu_self_test_sched, bool, 0444); + +static int rcu_self_test_counter; + +static void test_callback(struct rcu_head *r) +{ + rcu_self_test_counter++; + pr_info("RCU test callback executed %d\n", rcu_self_test_counter); +} + +static void early_boot_test_call_rcu(void) +{ + static struct rcu_head head; + + call_rcu(&head, test_callback); +} + +static void early_boot_test_call_rcu_bh(void) +{ + static struct rcu_head head; + + call_rcu_bh(&head, test_callback); +} + +static void early_boot_test_call_rcu_sched(void) +{ + static struct rcu_head head; + + call_rcu_sched(&head, test_callback); +} + +void rcu_early_boot_tests(void) +{ + pr_info("Running RCU self tests\n"); + + if (rcu_self_test) + early_boot_test_call_rcu(); + if (rcu_self_test_bh) + early_boot_test_call_rcu_bh(); + if (rcu_self_test_sched) + early_boot_test_call_rcu_sched(); + rcu_test_sync_prims(); +} + +static int rcu_verify_early_boot_tests(void) +{ + int ret = 0; + int early_boot_test_counter = 0; + + if (rcu_self_test) { + early_boot_test_counter++; + rcu_barrier(); + } + if (rcu_self_test_bh) { + early_boot_test_counter++; + rcu_barrier_bh(); + } + if (rcu_self_test_sched) { + early_boot_test_counter++; + rcu_barrier_sched(); + } + + if (rcu_self_test_counter != early_boot_test_counter) { + WARN_ON(1); + ret = -1; + } + + return ret; +} +late_initcall(rcu_verify_early_boot_tests); +#else +void rcu_early_boot_tests(void) {} +#endif /* CONFIG_PROVE_RCU */ + +#ifndef CONFIG_TINY_RCU + +/* + * Print any significant non-default boot-time settings. + */ +void __init rcupdate_announce_bootup_oddness(void) +{ + if (rcu_normal) + pr_info("\tNo expedited grace period (rcu_normal).\n"); + else if (rcu_normal_after_boot) + pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n"); + else if (rcu_expedited) + pr_info("\tAll grace periods are expedited (rcu_expedited).\n"); + if (rcu_cpu_stall_suppress) + pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n"); + if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT) + pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout); + rcu_tasks_bootup_oddness(); +} + +#endif /* #ifndef CONFIG_TINY_RCU */ |