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Diffstat (limited to 'kernel/rcu/tree.c')
| -rw-r--r-- | kernel/rcu/tree.c | 4625 |
1 files changed, 4625 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c new file mode 100644 index 000000000..06bfe61d3 --- /dev/null +++ b/kernel/rcu/tree.c @@ -0,0 +1,4625 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Read-Copy Update mechanism for mutual exclusion (tree-based version) + * + * Copyright IBM Corporation, 2008 + * + * Authors: Dipankar Sarma <dipankar@in.ibm.com> + * Manfred Spraul <manfred@colorfullife.com> + * Paul E. McKenney <paulmck@linux.ibm.com> + * + * Based on the original work by Paul McKenney <paulmck@linux.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/kmemleak.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/random.h> +#include <linux/trace_events.h> +#include <linux/suspend.h> +#include <linux/ftrace.h> +#include <linux/tick.h> +#include <linux/sysrq.h> +#include <linux/kprobes.h> +#include <linux/gfp.h> +#include <linux/oom.h> +#include <linux/smpboot.h> +#include <linux/jiffies.h> +#include <linux/slab.h> +#include <linux/sched/isolation.h> +#include <linux/sched/clock.h> +#include <linux/vmalloc.h> +#include <linux/mm.h> +#include <linux/kasan.h> +#include "../time/tick-internal.h" + +#include "tree.h" +#include "rcu.h" + +#ifdef MODULE_PARAM_PREFIX +#undef MODULE_PARAM_PREFIX +#endif +#define MODULE_PARAM_PREFIX "rcutree." + +/* Data structures. */ + +/* + * 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) + +static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = { + .dynticks_nesting = 1, + .dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE, + .dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR), +}; +static struct rcu_state rcu_state = { + .level = { &rcu_state.node[0] }, + .gp_state = RCU_GP_IDLE, + .gp_seq = (0UL - 300UL) << RCU_SEQ_CTR_SHIFT, + .barrier_mutex = __MUTEX_INITIALIZER(rcu_state.barrier_mutex), + .name = RCU_NAME, + .abbr = RCU_ABBR, + .exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex), + .exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex), + .ofl_lock = __RAW_SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock), +}; + +/* Dump rcu_node combining tree at boot to verify correct setup. */ +static bool dump_tree; +module_param(dump_tree, bool, 0444); +/* By default, use RCU_SOFTIRQ instead of rcuc kthreads. */ +static bool use_softirq = true; +module_param(use_softirq, 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. */ + +/* + * 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_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 rcu_report_exp_rdp(struct rcu_data *rdp); +static void sync_sched_exp_online_cleanup(int cpu); +static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp); + +/* rcuc/rcub kthread realtime priority */ +static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0; +module_param(kthread_prio, int, 0444); + +/* 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); + +// Add delay to rcu_read_unlock() for strict grace periods. +static int rcu_unlock_delay; +#ifdef CONFIG_RCU_STRICT_GRACE_PERIOD +module_param(rcu_unlock_delay, int, 0444); +#endif + +/* + * This rcu parameter is runtime-read-only. It reflects + * a minimum allowed number of objects which can be cached + * per-CPU. Object size is equal to one page. This value + * can be changed at boot time. + */ +static int rcu_min_cached_objs = 5; +module_param(rcu_min_cached_objs, int, 0444); + +/* Retrieve 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. + */ +static 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(void) +{ + return rcu_seq_state(rcu_seq_current(&rcu_state.gp_seq)); +} + +/* + * Return the number of callbacks queued on the specified CPU. + * Handles both the nocbs and normal cases. + */ +static long rcu_get_n_cbs_cpu(int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + + if (rcu_segcblist_is_enabled(&rdp->cblist)) + return rcu_segcblist_n_cbs(&rdp->cblist); + return 0; +} + +void rcu_softirq_qs(void) +{ + rcu_qs(); + rcu_preempt_deferred_qs(current); +} + +/* + * Record entry into an extended quiescent state. This is only to be + * called when not already in an extended quiescent state, that is, + * RCU is watching prior to the call to this function and is no longer + * watching upon return. + */ +static noinstr void rcu_dynticks_eqs_enter(void) +{ + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + 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. + */ + rcu_dynticks_task_trace_enter(); // Before ->dynticks update! + seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); + // RCU is no longer watching. Better be in 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, that is, RCU is not watching + * prior to the call to this function and is watching upon return. + */ +static noinstr void rcu_dynticks_eqs_exit(void) +{ + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + 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 = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); + // RCU is now watching. Better not be in an extended quiescent state! + rcu_dynticks_task_trace_exit(); // After ->dynticks update! + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && + !(seq & RCU_DYNTICK_CTRL_CTR)); + if (seq & RCU_DYNTICK_CTRL_MASK) { + arch_atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks); + smp_mb__after_atomic(); /* _exit after clearing mask. */ + } +} + +/* + * 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_data *rdp = this_cpu_ptr(&rcu_data); + + if (atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR) + return; + atomic_add(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); +} + +/* + * Is the current CPU in an extended quiescent state? + * + * No ordering, as we are sampling CPU-local information. + */ +static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void) +{ + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + + return !(arch_atomic_read(&rdp->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. + */ +static int rcu_dynticks_snap(struct rcu_data *rdp) +{ + int snap = atomic_add_return(0, &rdp->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_data + * 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_data *rdp, int snap) +{ + return snap != rcu_dynticks_snap(rdp); +} + +/* + * Return true if the referenced integer is zero while the specified + * CPU remains within a single extended quiescent state. + */ +bool rcu_dynticks_zero_in_eqs(int cpu, int *vp) +{ + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + int snap; + + // If not quiescent, force back to earlier extended quiescent state. + snap = atomic_read(&rdp->dynticks) & ~(RCU_DYNTICK_CTRL_MASK | + RCU_DYNTICK_CTRL_CTR); + + smp_rmb(); // Order ->dynticks and *vp reads. + if (READ_ONCE(*vp)) + return false; // Non-zero, so report failure; + smp_rmb(); // Order *vp read and ->dynticks re-read. + + // If still in the same extended quiescent state, we are good! + return snap == (atomic_read(&rdp->dynticks) & ~RCU_DYNTICK_CTRL_MASK); +} + +/* + * 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; + int new_old; + struct rcu_data *rdp = &per_cpu(rcu_data, cpu); + + new_old = atomic_read(&rdp->dynticks); + do { + old = new_old; + if (old & RCU_DYNTICK_CTRL_CTR) + return false; + new = old | RCU_DYNTICK_CTRL_MASK; + new_old = atomic_cmpxchg(&rdp->dynticks, old, new); + } while (new_old != 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. + */ +notrace void rcu_momentary_dyntick_idle(void) +{ + int special; + + raw_cpu_write(rcu_data.rcu_need_heavy_qs, false); + special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR, + &this_cpu_ptr(&rcu_data)->dynticks); + /* It is illegal to call this from idle state. */ + WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR)); + rcu_preempt_deferred_qs(current); +} +EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle); + +/** + * rcu_is_cpu_rrupt_from_idle - see if 'interrupted' from idle + * + * If the current CPU is idle and running at a first-level (not nested) + * interrupt, or directly, from idle, return true. + * + * The caller must have at least disabled IRQs. + */ +static int rcu_is_cpu_rrupt_from_idle(void) +{ + long nesting; + + /* + * Usually called from the tick; but also used from smp_function_call() + * for expedited grace periods. This latter can result in running from + * the idle task, instead of an actual IPI. + */ + lockdep_assert_irqs_disabled(); + + /* Check for counter underflows */ + RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) < 0, + "RCU dynticks_nesting counter underflow!"); + RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 0, + "RCU dynticks_nmi_nesting counter underflow/zero!"); + + /* Are we at first interrupt nesting level? */ + nesting = __this_cpu_read(rcu_data.dynticks_nmi_nesting); + if (nesting > 1) + return false; + + /* + * If we're not in an interrupt, we must be in the idle task! + */ + WARN_ON_ONCE(!nesting && !is_idle_task(current)); + + /* Does CPU appear to be idle from an RCU standpoint? */ + return __this_cpu_read(rcu_data.dynticks_nesting) == 0; +} + +#define DEFAULT_RCU_BLIMIT (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 1000 : 10) + // Maximum callbacks per rcu_do_batch ... +#define DEFAULT_MAX_RCU_BLIMIT 10000 // ... even during callback flood. +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; +#define DEFAULT_RCU_QOVLD_MULT 2 +#define DEFAULT_RCU_QOVLD (DEFAULT_RCU_QOVLD_MULT * DEFAULT_RCU_QHIMARK) +static long qovld = DEFAULT_RCU_QOVLD; // If this many pending, hammer QS. +static long qovld_calc = -1; // No pre-initialization lock acquisitions! + +module_param(blimit, long, 0444); +module_param(qhimark, long, 0444); +module_param(qlowmark, long, 0444); +module_param(qovld, long, 0444); + +static ulong jiffies_till_first_fqs = IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 0 : ULONG_MAX; +static ulong jiffies_till_next_fqs = ULONG_MAX; +static bool rcu_kick_kthreads; +static int rcu_divisor = 7; +module_param(rcu_divisor, int, 0644); + +/* Force an exit from rcu_do_batch() after 3 milliseconds. */ +static long rcu_resched_ns = 3 * NSEC_PER_MSEC; +module_param(rcu_resched_ns, long, 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 = ULONG_MAX; +module_param(jiffies_till_sched_qs, ulong, 0444); +static ulong jiffies_to_sched_qs; /* See adjust_jiffies_till_sched_qs(). */ +module_param(jiffies_to_sched_qs, ulong, 0444); /* Display only! */ + +/* + * Make sure that we give the grace-period kthread time to detect any + * idle CPUs before taking active measures to force quiescent states. + * However, don't go below 100 milliseconds, adjusted upwards for really + * large systems. + */ +static void adjust_jiffies_till_sched_qs(void) +{ + unsigned long j; + + /* If jiffies_till_sched_qs was specified, respect the request. */ + if (jiffies_till_sched_qs != ULONG_MAX) { + WRITE_ONCE(jiffies_to_sched_qs, jiffies_till_sched_qs); + return; + } + /* Otherwise, set to third fqs scan, but bound below on large system. */ + j = READ_ONCE(jiffies_till_first_fqs) + + 2 * READ_ONCE(jiffies_till_next_fqs); + if (j < HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV) + j = HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; + pr_info("RCU calculated value of scheduler-enlistment delay is %ld jiffies.\n", j); + WRITE_ONCE(jiffies_to_sched_qs, j); +} + +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); + adjust_jiffies_till_sched_qs(); + } + 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)); + adjust_jiffies_till_sched_qs(); + } + 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); + +static void force_qs_rnp(int (*f)(struct rcu_data *rdp)); +static int rcu_pending(int user); + +/* + * Return the number of RCU GPs completed thus far for debug & stats. + */ +unsigned long rcu_get_gp_seq(void) +{ + return READ_ONCE(rcu_state.gp_seq); +} +EXPORT_SYMBOL_GPL(rcu_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.expedited_sequence; +} +EXPORT_SYMBOL_GPL(rcu_exp_batches_completed); + +/* + * Return the root node of the rcu_state structure. + */ +static struct rcu_node *rcu_get_root(void) +{ + return &rcu_state.node[0]; +} + +/* + * 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) +{ + switch (test_type) { + case RCU_FLAVOR: + *flags = READ_ONCE(rcu_state.gp_flags); + *gp_seq = rcu_seq_current(&rcu_state.gp_seq); + break; + default: + break; + } +} +EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); + +/* + * 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 noinstr void rcu_eqs_enter(bool user) +{ + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + + WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE); + WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && + rdp->dynticks_nesting == 0); + if (rdp->dynticks_nesting != 1) { + // RCU will still be watching, so just do accounting and leave. + rdp->dynticks_nesting--; + return; + } + + lockdep_assert_irqs_disabled(); + instrumentation_begin(); + trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, atomic_read(&rdp->dynticks)); + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); + rdp = this_cpu_ptr(&rcu_data); + rcu_prepare_for_idle(); + rcu_preempt_deferred_qs(current); + + // instrumentation for the noinstr rcu_dynticks_eqs_enter() + instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks)); + + instrumentation_end(); + WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */ + // RCU is watching here ... + rcu_dynticks_eqs_enter(); + // ... but is no longer watching here. + 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); +} +EXPORT_SYMBOL_GPL(rcu_idle_enter); + +#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. + */ +noinstr void rcu_user_enter(void) +{ + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + + lockdep_assert_irqs_disabled(); + + instrumentation_begin(); + do_nocb_deferred_wakeup(rdp); + instrumentation_end(); + + 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 rdp->dynticks and rdp->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. + */ +noinstr void rcu_nmi_exit(void) +{ + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + + instrumentation_begin(); + /* + * 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(rdp->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 (rdp->dynticks_nmi_nesting != 1) { + trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, + atomic_read(&rdp->dynticks)); + WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */ + rdp->dynticks_nmi_nesting - 2); + instrumentation_end(); + return; + } + + /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ + trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks)); + WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ + + if (!in_nmi()) + rcu_prepare_for_idle(); + + // instrumentation for the noinstr rcu_dynticks_eqs_enter() + instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks)); + instrumentation_end(); + + // RCU is watching here ... + rcu_dynticks_eqs_enter(); + // ... but is no longer watching here. + + if (!in_nmi()) + rcu_dynticks_task_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 noinstr rcu_irq_exit(void) +{ + lockdep_assert_irqs_disabled(); + rcu_nmi_exit(); +} + +/** + * rcu_irq_exit_preempt - Inform RCU that current CPU is exiting irq + * towards in kernel preemption + * + * Same as rcu_irq_exit() but has a sanity check that scheduling is safe + * from RCU point of view. Invoked from return from interrupt before kernel + * preemption. + */ +void rcu_irq_exit_preempt(void) +{ + lockdep_assert_irqs_disabled(); + rcu_nmi_exit(); + + RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) <= 0, + "RCU dynticks_nesting counter underflow/zero!"); + RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) != + DYNTICK_IRQ_NONIDLE, + "Bad RCU dynticks_nmi_nesting counter\n"); + RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(), + "RCU in extended quiescent state!"); +} + +#ifdef CONFIG_PROVE_RCU +/** + * rcu_irq_exit_check_preempt - Validate that scheduling is possible + */ +void rcu_irq_exit_check_preempt(void) +{ + lockdep_assert_irqs_disabled(); + + RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) <= 0, + "RCU dynticks_nesting counter underflow/zero!"); + RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) != + DYNTICK_IRQ_NONIDLE, + "Bad RCU dynticks_nmi_nesting counter\n"); + RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(), + "RCU in extended quiescent state!"); +} +#endif /* #ifdef CONFIG_PROVE_RCU */ + +/* + * 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 noinstr rcu_eqs_exit(bool user) +{ + struct rcu_data *rdp; + long oldval; + + lockdep_assert_irqs_disabled(); + rdp = this_cpu_ptr(&rcu_data); + oldval = rdp->dynticks_nesting; + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0); + if (oldval) { + // RCU was already watching, so just do accounting and leave. + rdp->dynticks_nesting++; + return; + } + rcu_dynticks_task_exit(); + // RCU is not watching here ... + rcu_dynticks_eqs_exit(); + // ... but is watching here. + instrumentation_begin(); + + // instrumentation for the noinstr rcu_dynticks_eqs_exit() + instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks)); + + rcu_cleanup_after_idle(); + trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, atomic_read(&rdp->dynticks)); + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); + WRITE_ONCE(rdp->dynticks_nesting, 1); + WARN_ON_ONCE(rdp->dynticks_nmi_nesting); + WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE); + instrumentation_end(); +} + +/** + * 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); +} +EXPORT_SYMBOL_GPL(rcu_idle_exit); + +#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 noinstr rcu_user_exit(void) +{ + rcu_eqs_exit(1); +} + +/** + * __rcu_irq_enter_check_tick - Enable scheduler tick on CPU if RCU needs it. + * + * The scheduler tick is not normally enabled when CPUs enter the kernel + * from nohz_full userspace execution. After all, nohz_full userspace + * execution is an RCU quiescent state and the time executing in the kernel + * is quite short. Except of course when it isn't. And it is not hard to + * cause a large system to spend tens of seconds or even minutes looping + * in the kernel, which can cause a number of problems, include RCU CPU + * stall warnings. + * + * Therefore, if a nohz_full CPU fails to report a quiescent state + * in a timely manner, the RCU grace-period kthread sets that CPU's + * ->rcu_urgent_qs flag with the expectation that the next interrupt or + * exception will invoke this function, which will turn on the scheduler + * tick, which will enable RCU to detect that CPU's quiescent states, + * for example, due to cond_resched() calls in CONFIG_PREEMPT=n kernels. + * The tick will be disabled once a quiescent state is reported for + * this CPU. + * + * Of course, in carefully tuned systems, there might never be an + * interrupt or exception. In that case, the RCU grace-period kthread + * will eventually cause one to happen. However, in less carefully + * controlled environments, this function allows RCU to get what it + * needs without creating otherwise useless interruptions. + */ +void __rcu_irq_enter_check_tick(void) +{ + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + + // If we're here from NMI there's nothing to do. + if (in_nmi()) + return; + + RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(), + "Illegal rcu_irq_enter_check_tick() from extended quiescent state"); + + if (!tick_nohz_full_cpu(rdp->cpu) || + !READ_ONCE(rdp->rcu_urgent_qs) || + READ_ONCE(rdp->rcu_forced_tick)) { + // RCU doesn't need nohz_full help from this CPU, or it is + // already getting that help. + return; + } + + // We get here only when not in an extended quiescent state and + // from interrupts (as opposed to NMIs). Therefore, (1) RCU is + // already watching and (2) The fact that we are in an interrupt + // handler and that the rcu_node lock is an irq-disabled lock + // prevents self-deadlock. So we can safely recheck under the lock. + // Note that the nohz_full state currently cannot change. + raw_spin_lock_rcu_node(rdp->mynode); + if (rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) { + // A nohz_full CPU is in the kernel and RCU needs a + // quiescent state. Turn on the tick! + WRITE_ONCE(rdp->rcu_forced_tick, true); + tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU); + } + raw_spin_unlock_rcu_node(rdp->mynode); +} +NOKPROBE_SYMBOL(__rcu_irq_enter_check_tick); +#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 rdp->dynticks and + * rdp->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. + */ +noinstr void rcu_nmi_enter(void) +{ + long incby = 2; + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + + /* Complain about underflow. */ + WARN_ON_ONCE(rdp->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()) { + + if (!in_nmi()) + rcu_dynticks_task_exit(); + + // RCU is not watching here ... + rcu_dynticks_eqs_exit(); + // ... but is watching here. + + if (!in_nmi()) { + instrumentation_begin(); + rcu_cleanup_after_idle(); + instrumentation_end(); + } + + instrumentation_begin(); + // instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs() + instrument_atomic_read(&rdp->dynticks, sizeof(rdp->dynticks)); + // instrumentation for the noinstr rcu_dynticks_eqs_exit() + instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks)); + + incby = 1; + } else if (!in_nmi()) { + instrumentation_begin(); + rcu_irq_enter_check_tick(); + } else { + instrumentation_begin(); + } + + trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="), + rdp->dynticks_nmi_nesting, + rdp->dynticks_nmi_nesting + incby, atomic_read(&rdp->dynticks)); + instrumentation_end(); + WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */ + rdp->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. + */ +noinstr void rcu_irq_enter(void) +{ + lockdep_assert_irqs_disabled(); + rcu_nmi_enter(); +} + +/* + * 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); +} + +/* + * If any sort of urgency was applied to the current CPU (for example, + * the scheduler-clock interrupt was enabled on a nohz_full CPU) in order + * to get to a quiescent state, disable it. + */ +static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp) +{ + raw_lockdep_assert_held_rcu_node(rdp->mynode); + WRITE_ONCE(rdp->rcu_urgent_qs, false); + WRITE_ONCE(rdp->rcu_need_heavy_qs, false); + if (tick_nohz_full_cpu(rdp->cpu) && rdp->rcu_forced_tick) { + tick_dep_clear_cpu(rdp->cpu, TICK_DEP_BIT_RCU); + WRITE_ONCE(rdp->rcu_forced_tick, false); + } +} + +/** + * rcu_is_watching - see if RCU thinks that the current CPU is not 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 not in its idle loop or is in an interrupt or + * NMI handler, return true. + * + * Make notrace because it can be called by the internal functions of + * ftrace, and making this notrace removes unnecessary recursion calls. + */ +notrace bool 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_data.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. + * + * 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; + bool ret = false; + + if (in_nmi() || !rcu_scheduler_fully_active) + return true; + preempt_disable_notrace(); + rdp = this_cpu_ptr(&rcu_data); + rnp = rdp->mynode; + if (rdp->grpmask & rcu_rnp_online_cpus(rnp) || READ_ONCE(rnp->ofl_seq) & 0x1) + ret = true; + preempt_enable_notrace(); + return ret; +} +EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); + +#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ + +/* + * 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); + if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) { + trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti")); + rcu_gpnum_ovf(rdp->mynode, rdp); + return 1; + } + return 0; +} + +/* + * 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, rdp->dynticks_snap)) { + trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti")); + rcu_gpnum_ovf(rnp, rdp); + return 1; + } + + /* + * Complain if a CPU that is considered to be offline from RCU's + * perspective has not yet reported a quiescent state. After all, + * the offline CPU should have reported a quiescent state during + * the CPU-offline process, or, failing that, by rcu_gp_init() + * if it ran concurrently with either the CPU going offline or the + * last task on a leaf rcu_node structure exiting its RCU read-side + * critical section while all CPUs corresponding to that structure + * are offline. This added warning detects bugs in any of these + * code paths. + * + * The rcu_node structure's ->lock is held here, which excludes + * the relevant portions the CPU-hotplug code, the grace-period + * initialization code, and the rcu_read_unlock() code paths. + * + * For more detail, please refer to the "Hotplug CPU" section + * of RCU's Requirements documentation. + */ + if (WARN_ON_ONCE(!(rdp->grpmask & rcu_rnp_online_cpus(rnp)))) { + bool onl; + struct rcu_node *rnp1; + + 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: (1) At age jiffies_to_sched_qs, + * set .rcu_urgent_qs, (2) At age 2*jiffies_to_sched_qs, set + * both .rcu_need_heavy_qs and .rcu_urgent_qs. Note that the + * unsynchronized assignments to the per-CPU rcu_need_heavy_qs + * variable are safe because the assignments are repeated if this + * CPU failed to pass through a quiescent state. This code + * also checks .jiffies_resched in case jiffies_to_sched_qs + * is set way high. + */ + jtsq = READ_ONCE(jiffies_to_sched_qs); + ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu); + rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu); + if (!READ_ONCE(*rnhqp) && + (time_after(jiffies, rcu_state.gp_start + jtsq * 2) || + time_after(jiffies, rcu_state.jiffies_resched) || + rcu_state.cbovld)) { + WRITE_ONCE(*rnhqp, true); + /* Store rcu_need_heavy_qs before rcu_urgent_qs. */ + smp_store_release(ruqp, true); + } else if (time_after(jiffies, rcu_state.gp_start + jtsq)) { + WRITE_ONCE(*ruqp, true); + } + + /* + * NO_HZ_FULL CPUs can run in-kernel without rcu_sched_clock_irq! + * The above code handles this, but only for straight cond_resched(). + * And some in-kernel loops check need_resched() before calling + * cond_resched(), which defeats the above code for CPUs that are + * running in-kernel with scheduling-clock interrupts disabled. + * So hit them over the head with the resched_cpu() hammer! + */ + if (tick_nohz_full_cpu(rdp->cpu) && + (time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq * 3) || + rcu_state.cbovld)) { + WRITE_ONCE(*ruqp, true); + resched_cpu(rdp->cpu); + WRITE_ONCE(rdp->last_fqs_resched, jiffies); + } + + /* + * If more than halfway to RCU CPU stall-warning time, invoke + * resched_cpu() more frequently 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 (time_after(jiffies, rcu_state.jiffies_resched)) { + if (time_after(jiffies, + READ_ONCE(rdp->last_fqs_resched) + jtsq)) { + resched_cpu(rdp->cpu); + WRITE_ONCE(rdp->last_fqs_resched, jiffies); + } + 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); + atomic_set(&rdp->rcu_iw.flags, IRQ_WORK_HARD_IRQ); + rdp->rcu_iw_pending = true; + rdp->rcu_iw_gp_seq = rnp->gp_seq; + irq_work_queue_on(&rdp->rcu_iw, rdp->cpu); + } + } + + return 0; +} + +/* 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(rcu_state.name, READ_ONCE(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_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; + } + WRITE_ONCE(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()) { + 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(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_INIT); + WRITE_ONCE(rcu_state.gp_req_activity, jiffies); + if (!READ_ONCE(rcu_state.gp_kthread)) { + trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("NoGPkthread")); + goto unlock_out; + } + trace_rcu_grace_period(rcu_state.name, data_race(rcu_state.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)) { + WRITE_ONCE(rnp_start->gp_seq_needed, rnp->gp_seq_needed); + WRITE_ONCE(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_node *rnp) +{ + bool needmore; + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + + 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, in which case we just might immediately + * sleep upon return, resulting in a grace-period hang), and don't bother + * awakening when there is nothing for the grace-period kthread to do + * (as in several CPUs raced to awaken, 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(void) +{ + struct task_struct *t = READ_ONCE(rcu_state.gp_kthread); + + if ((current == t && !in_irq() && !in_serving_softirq()) || + !READ_ONCE(rcu_state.gp_flags) || !t) + return; + WRITE_ONCE(rcu_state.gp_wake_time, jiffies); + WRITE_ONCE(rcu_state.gp_wake_seq, READ_ONCE(rcu_state.gp_seq)); + swake_up_one(&rcu_state.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_node *rnp, struct rcu_data *rdp) +{ + unsigned long gp_seq_req; + bool ret = false; + + rcu_lockdep_assert_cblist_protected(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; + + /* + * 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(&rcu_state.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(rcu_state.name, gp_seq_req, TPS("AccWaitCB")); + else + trace_rcu_grace_period(rcu_state.name, gp_seq_req, 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_node *rnp, + struct rcu_data *rdp) +{ + unsigned long c; + bool needwake; + + rcu_lockdep_assert_cblist_protected(rdp); + c = rcu_seq_snap(&rcu_state.gp_seq); + if (!READ_ONCE(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(rnp, rdp); + raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ + if (needwake) + rcu_gp_kthread_wake(); +} + +/* + * 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_node *rnp, struct rcu_data *rdp) +{ + rcu_lockdep_assert_cblist_protected(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(rnp, rdp); +} + +/* + * Move and classify callbacks, but only if doing so won't require + * that the RCU grace-period kthread be awakened. + */ +static void __maybe_unused rcu_advance_cbs_nowake(struct rcu_node *rnp, + struct rcu_data *rdp) +{ + rcu_lockdep_assert_cblist_protected(rdp); + if (!rcu_seq_state(rcu_seq_current(&rnp->gp_seq)) || !raw_spin_trylock_rcu_node(rnp)) + return; + // The grace period cannot end while we hold the rcu_node lock. + if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) + WARN_ON_ONCE(rcu_advance_cbs(rnp, rdp)); + raw_spin_unlock_rcu_node(rnp); +} + +/* + * In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, attempt to generate a + * quiescent state. This is intended to be invoked when the CPU notices + * a new grace period. + */ +static void rcu_strict_gp_check_qs(void) +{ + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) { + rcu_read_lock(); + rcu_read_unlock(); + } +} + +/* + * 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_node *rnp, struct rcu_data *rdp) +{ + bool ret = false; + bool need_qs; + const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) && + rcu_segcblist_is_offloaded(&rdp->cblist); + + 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))) { + if (!offloaded) + ret = rcu_advance_cbs(rnp, rdp); /* Advance CBs. */ + rdp->core_needs_qs = false; + trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuend")); + } else { + if (!offloaded) + ret = rcu_accelerate_cbs(rnp, rdp); /* Recent CBs. */ + if (rdp->core_needs_qs) + rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask); + } + + /* 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(rcu_state.name, rnp->gp_seq, TPS("cpustart")); + need_qs = !!(rnp->qsmask & rdp->grpmask); + rdp->cpu_no_qs.b.norm = need_qs; + rdp->core_needs_qs = need_qs; + zero_cpu_stall_ticks(rdp); + } + rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */ + if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap) + WRITE_ONCE(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_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(rnp, rdp); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + rcu_strict_gp_check_qs(); + if (needwake) + rcu_gp_kthread_wake(); +} + +static void rcu_gp_slow(int delay) +{ + if (delay > 0 && + !(rcu_seq_ctr(rcu_state.gp_seq) % + (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay))) + schedule_timeout_idle(delay); +} + +static unsigned long sleep_duration; + +/* Allow rcutorture to stall the grace-period kthread. */ +void rcu_gp_set_torture_wait(int duration) +{ + if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST) && duration > 0) + WRITE_ONCE(sleep_duration, duration); +} +EXPORT_SYMBOL_GPL(rcu_gp_set_torture_wait); + +/* Actually implement the aforementioned wait. */ +static void rcu_gp_torture_wait(void) +{ + unsigned long duration; + + if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST)) + return; + duration = xchg(&sleep_duration, 0UL); + if (duration > 0) { + pr_alert("%s: Waiting %lu jiffies\n", __func__, duration); + schedule_timeout_idle(duration); + pr_alert("%s: Wait complete\n", __func__); + } +} + +/* + * Handler for on_each_cpu() to invoke the target CPU's RCU core + * processing. + */ +static void rcu_strict_gp_boundary(void *unused) +{ + invoke_rcu_core(); +} + +/* + * Initialize a new grace period. Return false if no grace period required. + */ +static bool rcu_gp_init(void) +{ + unsigned long firstseq; + unsigned long flags; + unsigned long oldmask; + unsigned long mask; + struct rcu_data *rdp; + struct rcu_node *rnp = rcu_get_root(); + + WRITE_ONCE(rcu_state.gp_activity, jiffies); + raw_spin_lock_irq_rcu_node(rnp); + if (!READ_ONCE(rcu_state.gp_flags)) { + /* Spurious wakeup, tell caller to go back to sleep. */ + raw_spin_unlock_irq_rcu_node(rnp); + return false; + } + WRITE_ONCE(rcu_state.gp_flags, 0); /* Clear all flags: New GP. */ + + if (WARN_ON_ONCE(rcu_gp_in_progress())) { + /* + * 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(); + /* Record GP times before starting GP, hence rcu_seq_start(). */ + rcu_seq_start(&rcu_state.gp_seq); + ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq); + trace_rcu_grace_period(rcu_state.name, rcu_state.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 RCU hooks in the CPU + * offlining path, when combined with checks in this function, + * will handle CPUs that are currently going offline or that will + * go offline later. Please also refer to "Hotplug CPU" section + * of RCU's Requirements documentation. + */ + rcu_state.gp_state = RCU_GP_ONOFF; + rcu_for_each_leaf_node(rnp) { + smp_mb(); // Pair with barriers used when updating ->ofl_seq to odd values. + firstseq = READ_ONCE(rnp->ofl_seq); + if (firstseq & 0x1) + while (firstseq == READ_ONCE(rnp->ofl_seq)) + schedule_timeout_idle(1); // Can't wake unless RCU is watching. + smp_mb(); // Pair with barriers used when updating ->ofl_seq to even values. + raw_spin_lock(&rcu_state.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); + raw_spin_unlock(&rcu_state.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); + raw_spin_unlock(&rcu_state.ofl_lock); + } + rcu_gp_slow(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 rcu_state.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. + */ + rcu_state.gp_state = RCU_GP_INIT; + rcu_for_each_node_breadth_first(rnp) { + rcu_gp_slow(gp_init_delay); + raw_spin_lock_irqsave_rcu_node(rnp, flags); + rdp = this_cpu_ptr(&rcu_data); + rcu_preempt_check_blocked_tasks(rnp); + rnp->qsmask = rnp->qsmaskinit; + WRITE_ONCE(rnp->gp_seq, rcu_state.gp_seq); + if (rnp == rdp->mynode) + (void)__note_gp_changes(rnp, rdp); + rcu_preempt_boost_start_gp(rnp); + trace_rcu_grace_period_init(rcu_state.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, rnp, rnp->gp_seq, flags); + else + raw_spin_unlock_irq_rcu_node(rnp); + cond_resched_tasks_rcu_qs(); + WRITE_ONCE(rcu_state.gp_activity, jiffies); + } + + // If strict, make all CPUs aware of new grace period. + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) + on_each_cpu(rcu_strict_gp_boundary, NULL, 0); + + return true; +} + +/* + * Helper function for swait_event_idle_exclusive() wakeup at force-quiescent-state + * time. + */ +static bool rcu_gp_fqs_check_wake(int *gfp) +{ + struct rcu_node *rnp = rcu_get_root(); + + // If under overload conditions, force an immediate FQS scan. + if (*gfp & RCU_GP_FLAG_OVLD) + return true; + + // Someone like call_rcu() requested a force-quiescent-state scan. + *gfp = READ_ONCE(rcu_state.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(bool first_time) +{ + struct rcu_node *rnp = rcu_get_root(); + + WRITE_ONCE(rcu_state.gp_activity, jiffies); + WRITE_ONCE(rcu_state.n_force_qs, rcu_state.n_force_qs + 1); + if (first_time) { + /* Collect dyntick-idle snapshots. */ + force_qs_rnp(dyntick_save_progress_counter); + } else { + /* Handle dyntick-idle and offline CPUs. */ + force_qs_rnp(rcu_implicit_dynticks_qs); + } + /* Clear flag to prevent immediate re-entry. */ + if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) { + raw_spin_lock_irq_rcu_node(rnp); + WRITE_ONCE(rcu_state.gp_flags, + READ_ONCE(rcu_state.gp_flags) & ~RCU_GP_FLAG_FQS); + raw_spin_unlock_irq_rcu_node(rnp); + } +} + +/* + * Loop doing repeated quiescent-state forcing until the grace period ends. + */ +static void rcu_gp_fqs_loop(void) +{ + bool first_gp_fqs; + int gf = 0; + unsigned long j; + int ret; + struct rcu_node *rnp = rcu_get_root(); + + first_gp_fqs = true; + j = READ_ONCE(jiffies_till_first_fqs); + if (rcu_state.cbovld) + gf = RCU_GP_FLAG_OVLD; + ret = 0; + for (;;) { + if (!ret) { + rcu_state.jiffies_force_qs = jiffies + j; + WRITE_ONCE(rcu_state.jiffies_kick_kthreads, + jiffies + (j ? 3 * j : 2)); + } + trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, + TPS("fqswait")); + rcu_state.gp_state = RCU_GP_WAIT_FQS; + ret = swait_event_idle_timeout_exclusive( + rcu_state.gp_wq, rcu_gp_fqs_check_wake(&gf), j); + rcu_gp_torture_wait(); + rcu_state.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 (!time_after(rcu_state.jiffies_force_qs, jiffies) || + (gf & (RCU_GP_FLAG_FQS | RCU_GP_FLAG_OVLD))) { + trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, + TPS("fqsstart")); + rcu_gp_fqs(first_gp_fqs); + gf = 0; + if (first_gp_fqs) { + first_gp_fqs = false; + gf = rcu_state.cbovld ? RCU_GP_FLAG_OVLD : 0; + } + trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, + TPS("fqsend")); + cond_resched_tasks_rcu_qs(); + WRITE_ONCE(rcu_state.gp_activity, jiffies); + ret = 0; /* Force full wait till next FQS. */ + j = READ_ONCE(jiffies_till_next_fqs); + } else { + /* Deal with stray signal. */ + cond_resched_tasks_rcu_qs(); + WRITE_ONCE(rcu_state.gp_activity, jiffies); + WARN_ON(signal_pending(current)); + trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, + TPS("fqswaitsig")); + ret = 1; /* Keep old FQS timing. */ + j = jiffies; + if (time_after(jiffies, rcu_state.jiffies_force_qs)) + j = 1; + else + j = rcu_state.jiffies_force_qs - j; + gf = 0; + } + } +} + +/* + * Clean up after the old grace period. + */ +static void rcu_gp_cleanup(void) +{ + int cpu; + bool needgp = false; + unsigned long gp_duration; + unsigned long new_gp_seq; + bool offloaded; + struct rcu_data *rdp; + struct rcu_node *rnp = rcu_get_root(); + struct swait_queue_head *sq; + + WRITE_ONCE(rcu_state.gp_activity, jiffies); + raw_spin_lock_irq_rcu_node(rnp); + rcu_state.gp_end = jiffies; + gp_duration = rcu_state.gp_end - rcu_state.gp_start; + if (gp_duration > rcu_state.gp_max) + rcu_state.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 = rcu_state.gp_seq; + rcu_seq_end(&new_gp_seq); + rcu_for_each_node_breadth_first(rnp) { + raw_spin_lock_irq_rcu_node(rnp); + if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp))) + dump_blkd_tasks(rnp, 10); + WARN_ON_ONCE(rnp->qsmask); + WRITE_ONCE(rnp->gp_seq, new_gp_seq); + rdp = this_cpu_ptr(&rcu_data); + if (rnp == rdp->mynode) + needgp = __note_gp_changes(rnp, rdp) || needgp; + /* smp_mb() provided by prior unlock-lock pair. */ + needgp = rcu_future_gp_cleanup(rnp) || needgp; + // Reset overload indication for CPUs no longer overloaded + if (rcu_is_leaf_node(rnp)) + for_each_leaf_node_cpu_mask(rnp, cpu, rnp->cbovldmask) { + rdp = per_cpu_ptr(&rcu_data, cpu); + check_cb_ovld_locked(rdp, rnp); + } + 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(rcu_state.gp_activity, jiffies); + rcu_gp_slow(gp_cleanup_delay); + } + rnp = rcu_get_root(); + raw_spin_lock_irq_rcu_node(rnp); /* GP before ->gp_seq update. */ + + /* Declare grace period done, trace first to use old GP number. */ + trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("end")); + rcu_seq_end(&rcu_state.gp_seq); + ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq); + rcu_state.gp_state = RCU_GP_IDLE; + /* Check for GP requests since above loop. */ + rdp = this_cpu_ptr(&rcu_data); + 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. */ + offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) && + rcu_segcblist_is_offloaded(&rdp->cblist); + if ((offloaded || !rcu_accelerate_cbs(rnp, rdp)) && needgp) { + WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT); + WRITE_ONCE(rcu_state.gp_req_activity, jiffies); + trace_rcu_grace_period(rcu_state.name, + rcu_state.gp_seq, + TPS("newreq")); + } else { + WRITE_ONCE(rcu_state.gp_flags, + rcu_state.gp_flags & RCU_GP_FLAG_INIT); + } + raw_spin_unlock_irq_rcu_node(rnp); + + // If strict, make all CPUs aware of the end of the old grace period. + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) + on_each_cpu(rcu_strict_gp_boundary, NULL, 0); +} + +/* + * Body of kthread that handles grace periods. + */ +static int __noreturn rcu_gp_kthread(void *unused) +{ + rcu_bind_gp_kthread(); + for (;;) { + + /* Handle grace-period start. */ + for (;;) { + trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, + TPS("reqwait")); + rcu_state.gp_state = RCU_GP_WAIT_GPS; + swait_event_idle_exclusive(rcu_state.gp_wq, + READ_ONCE(rcu_state.gp_flags) & + RCU_GP_FLAG_INIT); + rcu_gp_torture_wait(); + rcu_state.gp_state = RCU_GP_DONE_GPS; + /* Locking provides needed memory barrier. */ + if (rcu_gp_init()) + break; + cond_resched_tasks_rcu_qs(); + WRITE_ONCE(rcu_state.gp_activity, jiffies); + WARN_ON(signal_pending(current)); + trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, + TPS("reqwaitsig")); + } + + /* Handle quiescent-state forcing. */ + rcu_gp_fqs_loop(); + + /* Handle grace-period end. */ + rcu_state.gp_state = RCU_GP_CLEANUP; + rcu_gp_cleanup(); + rcu_state.gp_state = RCU_GP_CLEANED; + } +} + +/* + * Report a full set of quiescent states to the 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(unsigned long flags) + __releases(rcu_get_root()->lock) +{ + raw_lockdep_assert_held_rcu_node(rcu_get_root()); + WARN_ON_ONCE(!rcu_gp_in_progress()); + WRITE_ONCE(rcu_state.gp_flags, + READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); + raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(), flags); + rcu_gp_kthread_wake(); +} + +/* + * 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_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)); + WRITE_ONCE(rnp->qsmask, rnp->qsmask & ~mask); + trace_rcu_quiescent_state_report(rcu_state.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 = READ_ONCE(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(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 corresponding 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_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(!IS_ENABLED(CONFIG_PREEMPT_RCU)) || + 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(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, 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(struct rcu_data *rdp) +{ + unsigned long flags; + unsigned long mask; + bool needwake = false; + const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) && + rcu_segcblist_is_offloaded(&rdp->cblist); + struct rcu_node *rnp; + + WARN_ON_ONCE(rdp->cpu != smp_processor_id()); + 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. */ + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + mask = rdp->grpmask; + rdp->core_needs_qs = false; + if ((rnp->qsmask & mask) == 0) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } else { + /* + * This GP can't end until cpu checks in, so all of our + * callbacks can be processed during the next GP. + */ + if (!offloaded) + needwake = rcu_accelerate_cbs(rnp, rdp); + + rcu_disable_urgency_upon_qs(rdp); + rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); + /* ^^^ Released rnp->lock */ + if (needwake) + rcu_gp_kthread_wake(); + } +} + +/* + * 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_data *rdp) +{ + /* Check for grace-period ends and beginnings. */ + note_gp_changes(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); +} + +/* + * Near the end of the offline process. Trace the fact that this CPU + * is going offline. + */ +int rcutree_dying_cpu(unsigned int cpu) +{ + bool blkd; + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + struct rcu_node *rnp = rdp->mynode; + + if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) + return 0; + + blkd = !!(rnp->qsmask & rdp->grpmask); + trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq), + blkd ? TPS("cpuofl") : TPS("cpuofl-bgp")); + return 0; +} + +/* + * 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. + */ +int rcutree_dead_cpu(unsigned int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ + + if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) + return 0; + + /* Adjust any no-longer-needed kthreads. */ + rcu_boost_kthread_setaffinity(rnp, -1); + /* Do any needed no-CB deferred wakeups from this CPU. */ + do_nocb_deferred_wakeup(per_cpu_ptr(&rcu_data, cpu)); + + // Stop-machine done, so allow nohz_full to disable tick. + tick_dep_clear(TICK_DEP_BIT_RCU); + return 0; +} + +/* + * 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_data *rdp) +{ + int div; + unsigned long flags; + const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) && + rcu_segcblist_is_offloaded(&rdp->cblist); + struct rcu_head *rhp; + struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl); + long bl, count; + long pending, tlimit = 0; + + /* If no callbacks are ready, just return. */ + if (!rcu_segcblist_ready_cbs(&rdp->cblist)) { + trace_rcu_batch_start(rcu_state.name, + rcu_segcblist_n_cbs(&rdp->cblist), 0); + trace_rcu_batch_end(rcu_state.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); + rcu_nocb_lock(rdp); + WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); + pending = rcu_segcblist_n_cbs(&rdp->cblist); + div = READ_ONCE(rcu_divisor); + div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div; + bl = max(rdp->blimit, pending >> div); + if (in_serving_softirq() && unlikely(bl > 100)) { + long rrn = READ_ONCE(rcu_resched_ns); + + rrn = rrn < NSEC_PER_MSEC ? NSEC_PER_MSEC : rrn > NSEC_PER_SEC ? NSEC_PER_SEC : rrn; + tlimit = local_clock() + rrn; + } + trace_rcu_batch_start(rcu_state.name, + rcu_segcblist_n_cbs(&rdp->cblist), bl); + rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl); + if (offloaded) + rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); + rcu_nocb_unlock_irqrestore(rdp, flags); + + /* Invoke callbacks. */ + tick_dep_set_task(current, TICK_DEP_BIT_RCU); + rhp = rcu_cblist_dequeue(&rcl); + for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) { + rcu_callback_t f; + + debug_rcu_head_unqueue(rhp); + + rcu_lock_acquire(&rcu_callback_map); + trace_rcu_invoke_callback(rcu_state.name, rhp); + + f = rhp->func; + WRITE_ONCE(rhp->func, (rcu_callback_t)0L); + f(rhp); + + rcu_lock_release(&rcu_callback_map); + + /* + * Stop only if limit reached and CPU has something to do. + * Note: The rcl structure counts down from zero. + */ + if (in_serving_softirq()) { + if (-rcl.len >= bl && (need_resched() || + (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) + break; + + /* + * Make sure we don't spend too much time here and deprive other + * softirq vectors of CPU cycles. + */ + if (unlikely(tlimit)) { + /* only call local_clock() every 32 callbacks */ + if (likely((-rcl.len & 31) || local_clock() < tlimit)) + continue; + /* Exceeded the time limit, so leave. */ + break; + } + } else { + local_bh_enable(); + lockdep_assert_irqs_enabled(); + cond_resched_tasks_rcu_qs(); + lockdep_assert_irqs_enabled(); + local_bh_disable(); + } + } + + local_irq_save(flags); + rcu_nocb_lock(rdp); + count = -rcl.len; + rdp->n_cbs_invoked += count; + trace_rcu_batch_end(rcu_state.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 >= DEFAULT_MAX_RCU_BLIMIT && 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 = READ_ONCE(rcu_state.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(count == 0 && !rcu_segcblist_empty(&rdp->cblist)); + WARN_ON_ONCE(!IS_ENABLED(CONFIG_RCU_NOCB_CPU) && + count != 0 && rcu_segcblist_empty(&rdp->cblist)); + + rcu_nocb_unlock_irqrestore(rdp, flags); + + /* Re-invoke RCU core processing if there are callbacks remaining. */ + if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist)) + invoke_rcu_core(); + tick_dep_clear_task(current, TICK_DEP_BIT_RCU); +} + +/* + * This function is invoked from each scheduling-clock interrupt, + * and checks to see if this CPU is in a non-context-switch quiescent + * state, for example, user mode or idle loop. It also schedules RCU + * core processing. If the current grace period has gone on too long, + * it will ask the scheduler to manufacture a context switch for the sole + * purpose of providing a providing the needed quiescent state. + */ +void rcu_sched_clock_irq(int user) +{ + trace_rcu_utilization(TPS("Start scheduler-tick")); + lockdep_assert_irqs_disabled(); + raw_cpu_inc(rcu_data.ticks_this_gp); + /* The load-acquire pairs with the store-release setting to true. */ + if (smp_load_acquire(this_cpu_ptr(&rcu_data.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_data.rcu_urgent_qs, false); + } + rcu_flavor_sched_clock_irq(user); + if (rcu_pending(user)) + invoke_rcu_core(); + lockdep_assert_irqs_disabled(); + + trace_rcu_utilization(TPS("End scheduler-tick")); +} + +/* + * Scan the leaf rcu_node structures. For each structure on which all + * CPUs have reported a quiescent state and on which there are tasks + * blocking the current grace period, initiate RCU priority boosting. + * Otherwise, invoke the specified function to check dyntick state for + * each CPU that has not yet reported a quiescent state. + */ +static void force_qs_rnp(int (*f)(struct rcu_data *rdp)) +{ + int cpu; + unsigned long flags; + unsigned long mask; + struct rcu_data *rdp; + struct rcu_node *rnp; + + rcu_state.cbovld = rcu_state.cbovldnext; + rcu_state.cbovldnext = false; + rcu_for_each_leaf_node(rnp) { + cond_resched_tasks_rcu_qs(); + mask = 0; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + rcu_state.cbovldnext |= !!rnp->cbovldmask; + if (rnp->qsmask == 0) { + if (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_cpu_mask(rnp, cpu, rnp->qsmask) { + rdp = per_cpu_ptr(&rcu_data, cpu); + if (f(rdp)) { + mask |= rdp->grpmask; + rcu_disable_urgency_upon_qs(rdp); + } + } + if (mask != 0) { + /* Idle/offline CPUs, report (releases rnp->lock). */ + rcu_report_qs_rnp(mask, 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. + */ +void rcu_force_quiescent_state(void) +{ + unsigned long flags; + bool ret; + struct rcu_node *rnp; + struct rcu_node *rnp_old = NULL; + + /* Funnel through hierarchy to reduce memory contention. */ + rnp = raw_cpu_read(rcu_data.mynode); + for (; rnp != NULL; rnp = rnp->parent) { + ret = (READ_ONCE(rcu_state.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(), 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(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) { + raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); + return; /* Someone beat us to it. */ + } + WRITE_ONCE(rcu_state.gp_flags, + READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); + raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); + rcu_gp_kthread_wake(); +} +EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); + +// Workqueue handler for an RCU reader for kernels enforcing struct RCU +// grace periods. +static void strict_work_handler(struct work_struct *work) +{ + rcu_read_lock(); + rcu_read_unlock(); +} + +/* Perform RCU core processing work for the current CPU. */ +static __latent_entropy void rcu_core(void) +{ + unsigned long flags; + struct rcu_data *rdp = raw_cpu_ptr(&rcu_data); + struct rcu_node *rnp = rdp->mynode; + const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) && + rcu_segcblist_is_offloaded(&rdp->cblist); + + if (cpu_is_offline(smp_processor_id())) + return; + trace_rcu_utilization(TPS("Start RCU core")); + WARN_ON_ONCE(!rdp->beenonline); + + /* Report any deferred quiescent states if preemption enabled. */ + if (!(preempt_count() & PREEMPT_MASK)) { + rcu_preempt_deferred_qs(current); + } else if (rcu_preempt_need_deferred_qs(current)) { + set_tsk_need_resched(current); + set_preempt_need_resched(); + } + + /* Update RCU state based on any recent quiescent states. */ + rcu_check_quiescent_state(rdp); + + /* No grace period and unregistered callbacks? */ + if (!rcu_gp_in_progress() && + rcu_segcblist_is_enabled(&rdp->cblist) && !offloaded) { + local_irq_save(flags); + if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) + rcu_accelerate_cbs_unlocked(rnp, rdp); + local_irq_restore(flags); + } + + rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check()); + + /* If there are callbacks ready, invoke them. */ + if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist) && + likely(READ_ONCE(rcu_scheduler_fully_active))) + rcu_do_batch(rdp); + + /* Do any needed deferred wakeups of rcuo kthreads. */ + do_nocb_deferred_wakeup(rdp); + trace_rcu_utilization(TPS("End RCU core")); + + // If strict GPs, schedule an RCU reader in a clean environment. + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) + queue_work_on(rdp->cpu, rcu_gp_wq, &rdp->strict_work); +} + +static void rcu_core_si(struct softirq_action *h) +{ + rcu_core(); +} + +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 (t && (status != RCU_KTHREAD_YIELDING || is_idle_task(current))) + wake_up_process(t); +} + +static void invoke_rcu_core_kthread(void) +{ + struct task_struct *t; + unsigned long flags; + + local_irq_save(flags); + __this_cpu_write(rcu_data.rcu_cpu_has_work, 1); + t = __this_cpu_read(rcu_data.rcu_cpu_kthread_task); + if (t != NULL && t != current) + rcu_wake_cond(t, __this_cpu_read(rcu_data.rcu_cpu_kthread_status)); + local_irq_restore(flags); +} + +/* + * Wake up this CPU's rcuc kthread to do RCU core processing. + */ +static void invoke_rcu_core(void) +{ + if (!cpu_online(smp_processor_id())) + return; + if (use_softirq) + raise_softirq(RCU_SOFTIRQ); + else + invoke_rcu_core_kthread(); +} + +static void rcu_cpu_kthread_park(unsigned int cpu) +{ + per_cpu(rcu_data.rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; +} + +static int rcu_cpu_kthread_should_run(unsigned int cpu) +{ + return __this_cpu_read(rcu_data.rcu_cpu_has_work); +} + +/* + * Per-CPU kernel thread that invokes RCU callbacks. This replaces + * the RCU softirq used in 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_data.rcu_cpu_kthread_status); + char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work); + int spincnt; + + trace_rcu_utilization(TPS("Start CPU kthread@rcu_run")); + for (spincnt = 0; spincnt < 10; spincnt++) { + local_bh_disable(); + *statusp = RCU_KTHREAD_RUNNING; + local_irq_disable(); + work = *workp; + *workp = 0; + local_irq_enable(); + if (work) + rcu_core(); + 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_idle(2); + trace_rcu_utilization(TPS("End CPU kthread@rcu_yield")); + *statusp = RCU_KTHREAD_WAITING; +} + +static struct smp_hotplug_thread rcu_cpu_thread_spec = { + .store = &rcu_data.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 per-CPU RCU core processing kthreads. + */ +static int __init rcu_spawn_core_kthreads(void) +{ + int cpu; + + for_each_possible_cpu(cpu) + per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0; + if (!IS_ENABLED(CONFIG_RCU_BOOST) && use_softirq) + return 0; + WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec), + "%s: Could not start rcuc kthread, OOM is now expected behavior\n", __func__); + return 0; +} + +/* + * Handle any core-RCU processing required by a call_rcu() invocation. + */ +static void __call_rcu_core(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 rcu_force_quiescent_state() + * if some other CPU has recently done so. Also, don't bother + * invoking rcu_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(rdp); + + /* Start a new grace period if one not already started. */ + if (!rcu_gp_in_progress()) { + rcu_accelerate_cbs_unlocked(rdp->mynode, rdp); + } else { + /* Give the grace period a kick. */ + rdp->blimit = DEFAULT_MAX_RCU_BLIMIT; + if (READ_ONCE(rcu_state.n_force_qs) == rdp->n_force_qs_snap && + rcu_segcblist_first_pend_cb(&rdp->cblist) != head) + rcu_force_quiescent_state(); + rdp->n_force_qs_snap = READ_ONCE(rcu_state.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) +{ +} + +/* + * Check and if necessary update the leaf rcu_node structure's + * ->cbovldmask bit corresponding to the current CPU based on that CPU's + * number of queued RCU callbacks. The caller must hold the leaf rcu_node + * structure's ->lock. + */ +static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp) +{ + raw_lockdep_assert_held_rcu_node(rnp); + if (qovld_calc <= 0) + return; // Early boot and wildcard value set. + if (rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc) + WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask | rdp->grpmask); + else + WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask & ~rdp->grpmask); +} + +/* + * Check and if necessary update the leaf rcu_node structure's + * ->cbovldmask bit corresponding to the current CPU based on that CPU's + * number of queued RCU callbacks. No locks need be held, but the + * caller must have disabled interrupts. + * + * Note that this function ignores the possibility that there are a lot + * of callbacks all of which have already seen the end of their respective + * grace periods. This omission is due to the need for no-CBs CPUs to + * be holding ->nocb_lock to do this check, which is too heavy for a + * common-case operation. + */ +static void check_cb_ovld(struct rcu_data *rdp) +{ + struct rcu_node *const rnp = rdp->mynode; + + if (qovld_calc <= 0 || + ((rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc) == + !!(READ_ONCE(rnp->cbovldmask) & rdp->grpmask))) + return; // Early boot wildcard value or already set correctly. + raw_spin_lock_rcu_node(rnp); + check_cb_ovld_locked(rdp, rnp); + raw_spin_unlock_rcu_node(rnp); +} + +/* Helper function for call_rcu() and friends. */ +static void +__call_rcu(struct rcu_head *head, rcu_callback_t func) +{ + unsigned long flags; + struct rcu_data *rdp; + bool was_alldone; + + /* 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->%pS()!!!\n", + head, head->func); + WRITE_ONCE(head->func, rcu_leak_callback); + return; + } + head->func = func; + head->next = NULL; + local_irq_save(flags); + kasan_record_aux_stack(head); + rdp = this_cpu_ptr(&rcu_data); + + /* Add the callback to our list. */ + if (unlikely(!rcu_segcblist_is_enabled(&rdp->cblist))) { + // This can trigger due to call_rcu() from offline CPU: + WARN_ON_ONCE(rcu_scheduler_active != RCU_SCHEDULER_INACTIVE); + WARN_ON_ONCE(!rcu_is_watching()); + // Very early boot, before rcu_init(). Initialize if needed + // and then drop through to queue the callback. + if (rcu_segcblist_empty(&rdp->cblist)) + rcu_segcblist_init(&rdp->cblist); + } + + check_cb_ovld(rdp); + if (rcu_nocb_try_bypass(rdp, head, &was_alldone, flags)) + return; // Enqueued onto ->nocb_bypass, so just leave. + // If no-CBs CPU gets here, rcu_nocb_try_bypass() acquired ->nocb_lock. + rcu_segcblist_enqueue(&rdp->cblist, head); + if (__is_kvfree_rcu_offset((unsigned long)func)) + trace_rcu_kvfree_callback(rcu_state.name, head, + (unsigned long)func, + rcu_segcblist_n_cbs(&rdp->cblist)); + else + trace_rcu_callback(rcu_state.name, head, + rcu_segcblist_n_cbs(&rdp->cblist)); + + /* Go handle any RCU core processing required. */ + if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) && + unlikely(rcu_segcblist_is_offloaded(&rdp->cblist))) { + __call_rcu_nocb_wake(rdp, was_alldone, flags); /* unlocks */ + } else { + __call_rcu_core(rdp, head, flags); + local_irq_restore(flags); + } +} + +/** + * 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. In addition, regions of code across which interrupts, + * preemption, or softirqs have been disabled also serve as RCU read-side + * critical sections. This includes hardware interrupt handlers, softirq + * handlers, and NMI handlers. + * + * 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); +} +EXPORT_SYMBOL_GPL(call_rcu); + + +/* Maximum number of jiffies to wait before draining a batch. */ +#define KFREE_DRAIN_JIFFIES (HZ / 50) +#define KFREE_N_BATCHES 2 +#define FREE_N_CHANNELS 2 + +/** + * struct kvfree_rcu_bulk_data - single block to store kvfree_rcu() pointers + * @nr_records: Number of active pointers in the array + * @next: Next bulk object in the block chain + * @records: Array of the kvfree_rcu() pointers + */ +struct kvfree_rcu_bulk_data { + unsigned long nr_records; + struct kvfree_rcu_bulk_data *next; + void *records[]; +}; + +/* + * This macro defines how many entries the "records" array + * will contain. It is based on the fact that the size of + * kvfree_rcu_bulk_data structure becomes exactly one page. + */ +#define KVFREE_BULK_MAX_ENTR \ + ((PAGE_SIZE - sizeof(struct kvfree_rcu_bulk_data)) / sizeof(void *)) + +/** + * struct kfree_rcu_cpu_work - single batch of kfree_rcu() requests + * @rcu_work: Let queue_rcu_work() invoke workqueue handler after grace period + * @head_free: List of kfree_rcu() objects waiting for a grace period + * @bkvhead_free: Bulk-List of kvfree_rcu() objects waiting for a grace period + * @krcp: Pointer to @kfree_rcu_cpu structure + */ + +struct kfree_rcu_cpu_work { + struct rcu_work rcu_work; + struct rcu_head *head_free; + struct kvfree_rcu_bulk_data *bkvhead_free[FREE_N_CHANNELS]; + struct kfree_rcu_cpu *krcp; +}; + +/** + * struct kfree_rcu_cpu - batch up kfree_rcu() requests for RCU grace period + * @head: List of kfree_rcu() objects not yet waiting for a grace period + * @bkvhead: Bulk-List of kvfree_rcu() objects not yet waiting for a grace period + * @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period + * @lock: Synchronize access to this structure + * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES + * @monitor_todo: Tracks whether a @monitor_work delayed work is pending + * @initialized: The @rcu_work fields have been initialized + * @count: Number of objects for which GP not started + * @bkvcache: + * A simple cache list that contains objects for reuse purpose. + * In order to save some per-cpu space the list is singular. + * Even though it is lockless an access has to be protected by the + * per-cpu lock. + * @page_cache_work: A work to refill the cache when it is empty + * @work_in_progress: Indicates that page_cache_work is running + * @hrtimer: A hrtimer for scheduling a page_cache_work + * @nr_bkv_objs: number of allocated objects at @bkvcache. + * + * This is a per-CPU structure. The reason that it is not included in + * the rcu_data structure is to permit this code to be extracted from + * the RCU files. Such extraction could allow further optimization of + * the interactions with the slab allocators. + */ +struct kfree_rcu_cpu { + struct rcu_head *head; + struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS]; + struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES]; + raw_spinlock_t lock; + struct delayed_work monitor_work; + bool monitor_todo; + bool initialized; + int count; + + struct work_struct page_cache_work; + atomic_t work_in_progress; + struct hrtimer hrtimer; + + struct llist_head bkvcache; + int nr_bkv_objs; +}; + +static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = { + .lock = __RAW_SPIN_LOCK_UNLOCKED(krc.lock), +}; + +static __always_inline void +debug_rcu_bhead_unqueue(struct kvfree_rcu_bulk_data *bhead) +{ +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD + int i; + + for (i = 0; i < bhead->nr_records; i++) + debug_rcu_head_unqueue((struct rcu_head *)(bhead->records[i])); +#endif +} + +static inline struct kfree_rcu_cpu * +krc_this_cpu_lock(unsigned long *flags) +{ + struct kfree_rcu_cpu *krcp; + + local_irq_save(*flags); // For safely calling this_cpu_ptr(). + krcp = this_cpu_ptr(&krc); + raw_spin_lock(&krcp->lock); + + return krcp; +} + +static inline void +krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags) +{ + raw_spin_unlock(&krcp->lock); + local_irq_restore(flags); +} + +static inline struct kvfree_rcu_bulk_data * +get_cached_bnode(struct kfree_rcu_cpu *krcp) +{ + if (!krcp->nr_bkv_objs) + return NULL; + + krcp->nr_bkv_objs--; + return (struct kvfree_rcu_bulk_data *) + llist_del_first(&krcp->bkvcache); +} + +static inline bool +put_cached_bnode(struct kfree_rcu_cpu *krcp, + struct kvfree_rcu_bulk_data *bnode) +{ + // Check the limit. + if (krcp->nr_bkv_objs >= rcu_min_cached_objs) + return false; + + llist_add((struct llist_node *) bnode, &krcp->bkvcache); + krcp->nr_bkv_objs++; + return true; + +} + +/* + * This function is invoked in workqueue context after a grace period. + * It frees all the objects queued on ->bhead_free or ->head_free. + */ +static void kfree_rcu_work(struct work_struct *work) +{ + unsigned long flags; + struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS], *bnext; + struct rcu_head *head, *next; + struct kfree_rcu_cpu *krcp; + struct kfree_rcu_cpu_work *krwp; + int i, j; + + krwp = container_of(to_rcu_work(work), + struct kfree_rcu_cpu_work, rcu_work); + krcp = krwp->krcp; + + raw_spin_lock_irqsave(&krcp->lock, flags); + // Channels 1 and 2. + for (i = 0; i < FREE_N_CHANNELS; i++) { + bkvhead[i] = krwp->bkvhead_free[i]; + krwp->bkvhead_free[i] = NULL; + } + + // Channel 3. + head = krwp->head_free; + krwp->head_free = NULL; + raw_spin_unlock_irqrestore(&krcp->lock, flags); + + // Handle two first channels. + for (i = 0; i < FREE_N_CHANNELS; i++) { + for (; bkvhead[i]; bkvhead[i] = bnext) { + bnext = bkvhead[i]->next; + debug_rcu_bhead_unqueue(bkvhead[i]); + + rcu_lock_acquire(&rcu_callback_map); + if (i == 0) { // kmalloc() / kfree(). + trace_rcu_invoke_kfree_bulk_callback( + rcu_state.name, bkvhead[i]->nr_records, + bkvhead[i]->records); + + kfree_bulk(bkvhead[i]->nr_records, + bkvhead[i]->records); + } else { // vmalloc() / vfree(). + for (j = 0; j < bkvhead[i]->nr_records; j++) { + trace_rcu_invoke_kvfree_callback( + rcu_state.name, + bkvhead[i]->records[j], 0); + + vfree(bkvhead[i]->records[j]); + } + } + rcu_lock_release(&rcu_callback_map); + + raw_spin_lock_irqsave(&krcp->lock, flags); + if (put_cached_bnode(krcp, bkvhead[i])) + bkvhead[i] = NULL; + raw_spin_unlock_irqrestore(&krcp->lock, flags); + + if (bkvhead[i]) + free_page((unsigned long) bkvhead[i]); + + cond_resched_tasks_rcu_qs(); + } + } + + /* + * Emergency case only. It can happen under low memory + * condition when an allocation gets failed, so the "bulk" + * path can not be temporary maintained. + */ + for (; head; head = next) { + unsigned long offset = (unsigned long)head->func; + void *ptr = (void *)head - offset; + + next = head->next; + debug_rcu_head_unqueue((struct rcu_head *)ptr); + rcu_lock_acquire(&rcu_callback_map); + trace_rcu_invoke_kvfree_callback(rcu_state.name, head, offset); + + if (!WARN_ON_ONCE(!__is_kvfree_rcu_offset(offset))) + kvfree(ptr); + + rcu_lock_release(&rcu_callback_map); + cond_resched_tasks_rcu_qs(); + } +} + +static bool +need_offload_krc(struct kfree_rcu_cpu *krcp) +{ + int i; + + for (i = 0; i < FREE_N_CHANNELS; i++) + if (krcp->bkvhead[i]) + return true; + + return !!krcp->head; +} + +static bool +need_wait_for_krwp_work(struct kfree_rcu_cpu_work *krwp) +{ + int i; + + for (i = 0; i < FREE_N_CHANNELS; i++) + if (krwp->bkvhead_free[i]) + return true; + + return !!krwp->head_free; +} + +/* + * Schedule the kfree batch RCU work to run in workqueue context after a GP. + * + * This function is invoked by kfree_rcu_monitor() when the KFREE_DRAIN_JIFFIES + * timeout has been reached. + */ +static inline bool queue_kfree_rcu_work(struct kfree_rcu_cpu *krcp) +{ + struct kfree_rcu_cpu_work *krwp; + bool repeat = false; + int i, j; + + lockdep_assert_held(&krcp->lock); + + for (i = 0; i < KFREE_N_BATCHES; i++) { + krwp = &(krcp->krw_arr[i]); + + // Try to detach bulk_head or head and attach it, only when + // all channels are free. Any channel is not free means at krwp + // there is on-going rcu work to handle krwp's free business. + if (need_wait_for_krwp_work(krwp)) + continue; + + if (need_offload_krc(krcp)) { + // Channel 1 corresponds to SLAB ptrs. + // Channel 2 corresponds to vmalloc ptrs. + for (j = 0; j < FREE_N_CHANNELS; j++) { + if (!krwp->bkvhead_free[j]) { + krwp->bkvhead_free[j] = krcp->bkvhead[j]; + krcp->bkvhead[j] = NULL; + } + } + + // Channel 3 corresponds to emergency path. + if (!krwp->head_free) { + krwp->head_free = krcp->head; + krcp->head = NULL; + } + + WRITE_ONCE(krcp->count, 0); + + /* + * One work is per one batch, so there are three + * "free channels", the batch can handle. It can + * be that the work is in the pending state when + * channels have been detached following by each + * other. + */ + queue_rcu_work(system_wq, &krwp->rcu_work); + } + } + + // Repeat if any "free" corresponding channel is still busy. + if (need_offload_krc(krcp)) + repeat = true; + + return !repeat; +} + +static inline void kfree_rcu_drain_unlock(struct kfree_rcu_cpu *krcp, + unsigned long flags) +{ + // Attempt to start a new batch. + krcp->monitor_todo = false; + if (queue_kfree_rcu_work(krcp)) { + // Success! Our job is done here. + raw_spin_unlock_irqrestore(&krcp->lock, flags); + return; + } + + // Previous RCU batch still in progress, try again later. + krcp->monitor_todo = true; + schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); + raw_spin_unlock_irqrestore(&krcp->lock, flags); +} + +/* + * This function is invoked after the KFREE_DRAIN_JIFFIES timeout. + * It invokes kfree_rcu_drain_unlock() to attempt to start another batch. + */ +static void kfree_rcu_monitor(struct work_struct *work) +{ + unsigned long flags; + struct kfree_rcu_cpu *krcp = container_of(work, struct kfree_rcu_cpu, + monitor_work.work); + + raw_spin_lock_irqsave(&krcp->lock, flags); + if (krcp->monitor_todo) + kfree_rcu_drain_unlock(krcp, flags); + else + raw_spin_unlock_irqrestore(&krcp->lock, flags); +} + +static enum hrtimer_restart +schedule_page_work_fn(struct hrtimer *t) +{ + struct kfree_rcu_cpu *krcp = + container_of(t, struct kfree_rcu_cpu, hrtimer); + + queue_work(system_highpri_wq, &krcp->page_cache_work); + return HRTIMER_NORESTART; +} + +static void fill_page_cache_func(struct work_struct *work) +{ + struct kvfree_rcu_bulk_data *bnode; + struct kfree_rcu_cpu *krcp = + container_of(work, struct kfree_rcu_cpu, + page_cache_work); + unsigned long flags; + bool pushed; + int i; + + for (i = 0; i < rcu_min_cached_objs; i++) { + bnode = (struct kvfree_rcu_bulk_data *) + __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); + + if (!bnode) + break; + + raw_spin_lock_irqsave(&krcp->lock, flags); + pushed = put_cached_bnode(krcp, bnode); + raw_spin_unlock_irqrestore(&krcp->lock, flags); + + if (!pushed) { + free_page((unsigned long) bnode); + break; + } + } + + atomic_set(&krcp->work_in_progress, 0); +} + +static void +run_page_cache_worker(struct kfree_rcu_cpu *krcp) +{ + if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && + !atomic_xchg(&krcp->work_in_progress, 1)) { + hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, + HRTIMER_MODE_REL); + krcp->hrtimer.function = schedule_page_work_fn; + hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL); + } +} + +static inline bool +kvfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp, void *ptr) +{ + struct kvfree_rcu_bulk_data *bnode; + int idx; + + if (unlikely(!krcp->initialized)) + return false; + + lockdep_assert_held(&krcp->lock); + idx = !!is_vmalloc_addr(ptr); + + /* Check if a new block is required. */ + if (!krcp->bkvhead[idx] || + krcp->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) { + bnode = get_cached_bnode(krcp); + /* Switch to emergency path. */ + if (!bnode) + return false; + + /* Initialize the new block. */ + bnode->nr_records = 0; + bnode->next = krcp->bkvhead[idx]; + + /* Attach it to the head. */ + krcp->bkvhead[idx] = bnode; + } + + /* Finally insert. */ + krcp->bkvhead[idx]->records + [krcp->bkvhead[idx]->nr_records++] = ptr; + + return true; +} + +/* + * Queue a request for lazy invocation of appropriate free routine after a + * grace period. Please note there are three paths are maintained, two are the + * main ones that use array of pointers interface and third one is emergency + * one, that is used only when the main path can not be maintained temporary, + * due to memory pressure. + * + * Each kvfree_call_rcu() request is added to a batch. The batch will be drained + * every KFREE_DRAIN_JIFFIES number of jiffies. All the objects in the batch will + * be free'd in workqueue context. This allows us to: batch requests together to + * reduce the number of grace periods during heavy kfree_rcu()/kvfree_rcu() load. + */ +void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) +{ + unsigned long flags; + struct kfree_rcu_cpu *krcp; + bool success; + void *ptr; + + if (head) { + ptr = (void *) head - (unsigned long) func; + } else { + /* + * Please note there is a limitation for the head-less + * variant, that is why there is a clear rule for such + * objects: it can be used from might_sleep() context + * only. For other places please embed an rcu_head to + * your data. + */ + might_sleep(); + ptr = (unsigned long *) func; + } + + krcp = krc_this_cpu_lock(&flags); + + // Queue the object but don't yet schedule the batch. + if (debug_rcu_head_queue(ptr)) { + // Probable double kfree_rcu(), just leak. + WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n", + __func__, head); + + // Mark as success and leave. + success = true; + goto unlock_return; + } + + success = kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr); + if (!success) { + run_page_cache_worker(krcp); + + if (head == NULL) + // Inline if kvfree_rcu(one_arg) call. + goto unlock_return; + + head->func = func; + head->next = krcp->head; + krcp->head = head; + success = true; + } + + WRITE_ONCE(krcp->count, krcp->count + 1); + + /* + * The kvfree_rcu() caller considers the pointer freed at this point + * and likely removes any references to it. Since the actual slab + * freeing (and kmemleak_free()) is deferred, tell kmemleak to ignore + * this object (no scanning or false positives reporting). + */ + kmemleak_ignore(ptr); + + // Set timer to drain after KFREE_DRAIN_JIFFIES. + if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && + !krcp->monitor_todo) { + krcp->monitor_todo = true; + schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); + } + +unlock_return: + krc_this_cpu_unlock(krcp, flags); + + /* + * Inline kvfree() after synchronize_rcu(). We can do + * it from might_sleep() context only, so the current + * CPU can pass the QS state. + */ + if (!success) { + debug_rcu_head_unqueue((struct rcu_head *) ptr); + synchronize_rcu(); + kvfree(ptr); + } +} +EXPORT_SYMBOL_GPL(kvfree_call_rcu); + +static unsigned long +kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc) +{ + int cpu; + unsigned long count = 0; + + /* Snapshot count of all CPUs */ + for_each_possible_cpu(cpu) { + struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); + + count += READ_ONCE(krcp->count); + } + + return count; +} + +static unsigned long +kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) +{ + int cpu, freed = 0; + unsigned long flags; + + for_each_possible_cpu(cpu) { + int count; + struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); + + count = krcp->count; + raw_spin_lock_irqsave(&krcp->lock, flags); + if (krcp->monitor_todo) + kfree_rcu_drain_unlock(krcp, flags); + else + raw_spin_unlock_irqrestore(&krcp->lock, flags); + + sc->nr_to_scan -= count; + freed += count; + + if (sc->nr_to_scan <= 0) + break; + } + + return freed == 0 ? SHRINK_STOP : freed; +} + +static struct shrinker kfree_rcu_shrinker = { + .count_objects = kfree_rcu_shrink_count, + .scan_objects = kfree_rcu_shrink_scan, + .batch = 0, + .seeks = DEFAULT_SEEKS, +}; + +void __init kfree_rcu_scheduler_running(void) +{ + int cpu; + unsigned long flags; + + for_each_possible_cpu(cpu) { + struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); + + raw_spin_lock_irqsave(&krcp->lock, flags); + if (!krcp->head || krcp->monitor_todo) { + raw_spin_unlock_irqrestore(&krcp->lock, flags); + continue; + } + krcp->monitor_todo = true; + schedule_delayed_work_on(cpu, &krcp->monitor_work, + KFREE_DRAIN_JIFFIES); + raw_spin_unlock_irqrestore(&krcp->lock, flags); + } +} + +/* + * During early boot, any blocking grace-period wait automatically + * implies a grace period. Later on, this is never the case for PREEMPTION. + * + * Howevr, because a context switch is a grace period for !PREEMPTION, 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_rcu() or synchronize_rcu_expedited(). 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; + + if (IS_ENABLED(CONFIG_PREEMPTION)) + return rcu_scheduler_active == RCU_SCHEDULER_INACTIVE; + might_sleep(); /* Check for RCU read-side critical section. */ + preempt_disable(); + ret = num_online_cpus() <= 1; + preempt_enable(); + return ret; +} + +/** + * 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. + * In addition, regions of code across which interrupts, preemption, or + * softirqs have been disabled also serve as RCU read-side critical + * sections. This includes hardware interrupt handlers, softirq handlers, + * and NMI handlers. + * + * Note that this guarantee implies further memory-ordering guarantees. + * On systems with more than one CPU, when synchronize_rcu() returns, + * 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 synchronize_rcu(). In addition, each CPU having + * an RCU read-side critical section that extends beyond the return from + * synchronize_rcu() is guaranteed to have executed a full memory barrier + * after the beginning of synchronize_rcu() 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_rcu(), 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() -- 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(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_blocking_is_gp()) + return; + if (rcu_gp_is_expedited()) + synchronize_rcu_expedited(); + else + wait_rcu_gp(call_rcu); +} +EXPORT_SYMBOL_GPL(synchronize_rcu); + +/** + * 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.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.gp_seq, oldstate)) + synchronize_rcu(); + else + smp_mb(); /* Ensure GP ends before subsequent accesses. */ +} +EXPORT_SYMBOL_GPL(cond_synchronize_rcu); + +/* + * Check to see if there is any immediate RCU-related work to be done by + * the current CPU, returning 1 if so and zero otherwise. 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(int user) +{ + bool gp_in_progress; + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + struct rcu_node *rnp = rdp->mynode; + + lockdep_assert_irqs_disabled(); + + /* Check for CPU stalls, if enabled. */ + check_cpu_stall(rdp); + + /* Does this CPU need a deferred NOCB wakeup? */ + if (rcu_nocb_need_deferred_wakeup(rdp)) + return 1; + + /* Is this a nohz_full CPU in userspace or idle? (Ignore RCU if so.) */ + if ((user || rcu_is_cpu_rrupt_from_idle()) && rcu_nohz_full_cpu()) + return 0; + + /* Is the RCU core waiting for a quiescent state from this CPU? */ + gp_in_progress = rcu_gp_in_progress(); + if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm && gp_in_progress) + 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 (!gp_in_progress && rcu_segcblist_is_enabled(&rdp->cblist) && + (!IS_ENABLED(CONFIG_RCU_NOCB_CPU) || + !rcu_segcblist_is_offloaded(&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; + + /* nothing to do */ + return 0; +} + +/* + * Helper function for rcu_barrier() tracing. If tracing is disabled, + * the compiler is expected to optimize this away. + */ +static void rcu_barrier_trace(const char *s, int cpu, unsigned long done) +{ + trace_rcu_barrier(rcu_state.name, s, cpu, + atomic_read(&rcu_state.barrier_cpu_count), done); +} + +/* + * RCU callback function for rcu_barrier(). If we are last, wake + * up the task executing rcu_barrier(). + * + * Note that the value of rcu_state.barrier_sequence must be captured + * before the atomic_dec_and_test(). Otherwise, if this CPU is not last, + * other CPUs might count the value down to zero before this CPU gets + * around to invoking rcu_barrier_trace(), which might result in bogus + * data from the next instance of rcu_barrier(). + */ +static void rcu_barrier_callback(struct rcu_head *rhp) +{ + unsigned long __maybe_unused s = rcu_state.barrier_sequence; + + if (atomic_dec_and_test(&rcu_state.barrier_cpu_count)) { + rcu_barrier_trace(TPS("LastCB"), -1, s); + complete(&rcu_state.barrier_completion); + } else { + rcu_barrier_trace(TPS("CB"), -1, s); + } +} + +/* + * Called with preemption disabled, and from cross-cpu IRQ context. + */ +static void rcu_barrier_func(void *cpu_in) +{ + uintptr_t cpu = (uintptr_t)cpu_in; + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + + rcu_barrier_trace(TPS("IRQ"), -1, rcu_state.barrier_sequence); + rdp->barrier_head.func = rcu_barrier_callback; + debug_rcu_head_queue(&rdp->barrier_head); + rcu_nocb_lock(rdp); + WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, jiffies)); + if (rcu_segcblist_entrain(&rdp->cblist, &rdp->barrier_head)) { + atomic_inc(&rcu_state.barrier_cpu_count); + } else { + debug_rcu_head_unqueue(&rdp->barrier_head); + rcu_barrier_trace(TPS("IRQNQ"), -1, + rcu_state.barrier_sequence); + } + rcu_nocb_unlock(rdp); +} + +/** + * 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) +{ + uintptr_t cpu; + struct rcu_data *rdp; + unsigned long s = rcu_seq_snap(&rcu_state.barrier_sequence); + + rcu_barrier_trace(TPS("Begin"), -1, s); + + /* Take mutex to serialize concurrent rcu_barrier() requests. */ + mutex_lock(&rcu_state.barrier_mutex); + + /* Did someone else do our work for us? */ + if (rcu_seq_done(&rcu_state.barrier_sequence, s)) { + rcu_barrier_trace(TPS("EarlyExit"), -1, + rcu_state.barrier_sequence); + smp_mb(); /* caller's subsequent code after above check. */ + mutex_unlock(&rcu_state.barrier_mutex); + return; + } + + /* Mark the start of the barrier operation. */ + rcu_seq_start(&rcu_state.barrier_sequence); + rcu_barrier_trace(TPS("Inc1"), -1, rcu_state.barrier_sequence); + + /* + * Initialize the count to two rather than to zero in order + * to avoid a too-soon return to zero in case of an immediate + * invocation of the just-enqueued callback (or preemption of + * this task). Exclude CPU-hotplug operations to ensure that no + * offline non-offloaded CPU has callbacks queued. + */ + init_completion(&rcu_state.barrier_completion); + atomic_set(&rcu_state.barrier_cpu_count, 2); + 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) { + rdp = per_cpu_ptr(&rcu_data, cpu); + if (cpu_is_offline(cpu) && + !rcu_segcblist_is_offloaded(&rdp->cblist)) + continue; + if (rcu_segcblist_n_cbs(&rdp->cblist) && cpu_online(cpu)) { + rcu_barrier_trace(TPS("OnlineQ"), cpu, + rcu_state.barrier_sequence); + smp_call_function_single(cpu, rcu_barrier_func, (void *)cpu, 1); + } else if (rcu_segcblist_n_cbs(&rdp->cblist) && + cpu_is_offline(cpu)) { + rcu_barrier_trace(TPS("OfflineNoCBQ"), cpu, + rcu_state.barrier_sequence); + local_irq_disable(); + rcu_barrier_func((void *)cpu); + local_irq_enable(); + } else if (cpu_is_offline(cpu)) { + rcu_barrier_trace(TPS("OfflineNoCBNoQ"), cpu, + rcu_state.barrier_sequence); + } else { + rcu_barrier_trace(TPS("OnlineNQ"), cpu, + rcu_state.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_sub_and_test(2, &rcu_state.barrier_cpu_count)) + complete(&rcu_state.barrier_completion); + + /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ + wait_for_completion(&rcu_state.barrier_completion); + + /* Mark the end of the barrier operation. */ + rcu_barrier_trace(TPS("Inc2"), -1, rcu_state.barrier_sequence); + rcu_seq_end(&rcu_state.barrier_sequence); + + /* Other rcu_barrier() invocations can now safely proceed. */ + mutex_unlock(&rcu_state.barrier_mutex); +} +EXPORT_SYMBOL_GPL(rcu_barrier); + +/* + * 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_data *rdp = per_cpu_ptr(&rcu_data, cpu); + + /* Set up local state, ensuring consistent view of global state. */ + rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu); + INIT_WORK(&rdp->strict_work, strict_work_handler); + WARN_ON_ONCE(rdp->dynticks_nesting != 1); + WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp))); + rdp->rcu_ofl_gp_seq = rcu_state.gp_seq; + rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED; + rdp->rcu_onl_gp_seq = rcu_state.gp_seq; + rdp->rcu_onl_gp_flags = RCU_GP_CLEANED; + rdp->cpu = cpu; + rcu_boot_init_nocb_percpu_data(rdp); +} + +/* + * Invoked early in the CPU-online process, when pretty much all services + * are available. The incoming CPU is not present. + * + * Initializes 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 non-offloaded RCU callbacks in flight yet. + * And any offloaded callbacks are being numbered elsewhere. + */ +int rcutree_prepare_cpu(unsigned int cpu) +{ + unsigned long flags; + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + struct rcu_node *rnp = rcu_get_root(); + + /* 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 = READ_ONCE(rcu_state.n_force_qs); + rdp->blimit = blimit; + if (rcu_segcblist_empty(&rdp->cblist) && /* No early-boot CBs? */ + !rcu_segcblist_is_offloaded(&rdp->cblist)) + rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */ + rdp->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 = READ_ONCE(rnp->gp_seq); + rdp->gp_seq_needed = rdp->gp_seq; + rdp->cpu_no_qs.b.norm = true; + rdp->core_needs_qs = false; + rdp->rcu_iw_pending = false; + rdp->rcu_iw_gp_seq = rdp->gp_seq - 1; + trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl")); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + rcu_prepare_kthreads(cpu); + rcu_spawn_cpu_nocb_kthread(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_data, 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; + + rdp = per_cpu_ptr(&rcu_data, 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 (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); + + // Stop-machine done, so allow nohz_full to disable tick. + tick_dep_clear(TICK_DEP_BIT_RCU); + 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; + + rdp = per_cpu_ptr(&rcu_data, 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); + + // nohz_full CPUs need the tick for stop-machine to work quickly + tick_dep_set(TICK_DEP_BIT_RCU); + return 0; +} + +/* + * 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; + struct rcu_data *rdp; + struct rcu_node *rnp; + bool newcpu; + + rdp = per_cpu_ptr(&rcu_data, cpu); + if (rdp->cpu_started) + return; + rdp->cpu_started = true; + + rnp = rdp->mynode; + mask = rdp->grpmask; + WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1); + WARN_ON_ONCE(!(rnp->ofl_seq & 0x1)); + smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier(). + raw_spin_lock_irqsave_rcu_node(rnp, flags); + WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext | mask); + newcpu = !(rnp->expmaskinitnext & mask); + rnp->expmaskinitnext |= mask; + /* Allow lockless access for expedited grace periods. */ + smp_store_release(&rcu_state.ncpus, rcu_state.ncpus + newcpu); /* ^^^ */ + ASSERT_EXCLUSIVE_WRITER(rcu_state.ncpus); + rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */ + rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq); + rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags); + if (rnp->qsmask & mask) { /* RCU waiting on incoming CPU? */ + rcu_disable_urgency_upon_qs(rdp); + /* Report QS -after- changing ->qsmaskinitnext! */ + rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); + } else { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier(). + WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1); + WARN_ON_ONCE(rnp->ofl_seq & 0x1); + smp_mb(); /* Ensure RCU read-side usage follows above initialization. */ +} + +/* + * The outgoing function has no further need of RCU, so remove it from + * the rcu_node tree's ->qsmaskinitnext bit masks. + * + * 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) +{ + unsigned long flags; + unsigned long mask; + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ + + /* QS for any half-done expedited grace period. */ + preempt_disable(); + rcu_report_exp_rdp(this_cpu_ptr(&rcu_data)); + preempt_enable(); + rcu_preempt_deferred_qs(current); + + /* Remove outgoing CPU from mask in the leaf rcu_node structure. */ + mask = rdp->grpmask; + WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1); + WARN_ON_ONCE(!(rnp->ofl_seq & 0x1)); + smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier(). + raw_spin_lock(&rcu_state.ofl_lock); + raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */ + rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq); + rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags); + if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */ + /* Report quiescent state -before- changing ->qsmaskinitnext! */ + rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); + raw_spin_lock_irqsave_rcu_node(rnp, flags); + } + WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext & ~mask); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + raw_spin_unlock(&rcu_state.ofl_lock); + smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier(). + WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1); + WARN_ON_ONCE(rnp->ofl_seq & 0x1); + + rdp->cpu_started = false; +} + +#ifdef CONFIG_HOTPLUG_CPU +/* + * 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. Migrate the outgoing CPU's callbacks to the current CPU. + */ +void rcutree_migrate_callbacks(int cpu) +{ + unsigned long flags; + struct rcu_data *my_rdp; + struct rcu_node *my_rnp; + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + bool needwake; + + if (rcu_segcblist_is_offloaded(&rdp->cblist) || + rcu_segcblist_empty(&rdp->cblist)) + return; /* No callbacks to migrate. */ + + local_irq_save(flags); + my_rdp = this_cpu_ptr(&rcu_data); + my_rnp = my_rdp->mynode; + rcu_nocb_lock(my_rdp); /* irqs already disabled. */ + WARN_ON_ONCE(!rcu_nocb_flush_bypass(my_rdp, NULL, jiffies)); + raw_spin_lock_rcu_node(my_rnp); /* irqs already disabled. */ + /* Leverage recent GPs and set GP for new callbacks. */ + needwake = rcu_advance_cbs(my_rnp, rdp) || + rcu_advance_cbs(my_rnp, my_rdp); + rcu_segcblist_merge(&my_rdp->cblist, &rdp->cblist); + needwake = needwake || rcu_advance_cbs(my_rnp, my_rdp); + rcu_segcblist_disable(&rdp->cblist); + WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) != + !rcu_segcblist_n_cbs(&my_rdp->cblist)); + if (rcu_segcblist_is_offloaded(&my_rdp->cblist)) { + raw_spin_unlock_rcu_node(my_rnp); /* irqs remain disabled. */ + __call_rcu_nocb_wake(my_rdp, true, flags); + } else { + rcu_nocb_unlock(my_rdp); /* irqs remain disabled. */ + raw_spin_unlock_irqrestore_rcu_node(my_rnp, flags); + } + if (needwake) + rcu_gp_kthread_wake(); + lockdep_assert_irqs_enabled(); + 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)); +} +#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: + rcu_expedite_gp(); + break; + case PM_POST_HIBERNATION: + case PM_POST_SUSPEND: + rcu_unexpedite_gp(); + break; + default: + break; + } + return NOTIFY_OK; +} + +/* + * Spawn the kthreads that handle RCU'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 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; + t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name); + if (WARN_ONCE(IS_ERR(t), "%s: Could not start grace-period kthread, OOM is now expected behavior\n", __func__)) + return 0; + if (kthread_prio) { + sp.sched_priority = kthread_prio; + sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); + } + rnp = rcu_get_root(); + raw_spin_lock_irqsave_rcu_node(rnp, flags); + WRITE_ONCE(rcu_state.gp_activity, jiffies); + WRITE_ONCE(rcu_state.gp_req_activity, jiffies); + // Reset .gp_activity and .gp_req_activity before setting .gp_kthread. + smp_store_release(&rcu_state.gp_kthread, t); /* ^^^ */ + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + wake_up_process(t); + rcu_spawn_nocb_kthreads(); + rcu_spawn_boost_kthreads(); + rcu_spawn_core_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 the rcu_state structure. + */ +static void __init rcu_init_one(void) +{ + 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++) + rcu_state.level[i] = + rcu_state.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 = rcu_state.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 = rcu_state.gp_seq; + rnp->gp_seq_needed = rcu_state.gp_seq; + rnp->completedqs = rcu_state.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 = BIT(rnp->grpnum); + rnp->parent = rcu_state.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(&rcu_state.gp_wq); + init_swait_queue_head(&rcu_state.expedited_wq); + rnp = rcu_first_leaf_node(); + for_each_possible_cpu(i) { + while (i > rnp->grphi) + rnp++; + per_cpu_ptr(&rcu_data, i)->mynode = rnp; + rcu_boot_init_percpu_data(i); + } +} + +/* + * 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. + */ +void rcu_init_geometry(void) +{ + ulong d; + int i; + static unsigned long old_nr_cpu_ids; + int rcu_capacity[RCU_NUM_LVLS]; + static bool initialized; + + if (initialized) { + /* + * Warn if setup_nr_cpu_ids() had not yet been invoked, + * unless nr_cpus_ids == NR_CPUS, in which case who cares? + */ + WARN_ON_ONCE(old_nr_cpu_ids != nr_cpu_ids); + return; + } + + old_nr_cpu_ids = nr_cpu_ids; + initialized = true; + + /* + * 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; + adjust_jiffies_till_sched_qs(); + + /* 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. + */ +static void __init rcu_dump_rcu_node_tree(void) +{ + int level = 0; + struct rcu_node *rnp; + + pr_info("rcu_node tree layout dump\n"); + pr_info(" "); + rcu_for_each_node_breadth_first(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; + +static void __init kfree_rcu_batch_init(void) +{ + int cpu; + int i; + + for_each_possible_cpu(cpu) { + struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); + + for (i = 0; i < KFREE_N_BATCHES; i++) { + INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work); + krcp->krw_arr[i].krcp = krcp; + } + + INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor); + INIT_WORK(&krcp->page_cache_work, fill_page_cache_func); + krcp->initialized = true; + } + if (register_shrinker(&kfree_rcu_shrinker)) + pr_err("Failed to register kfree_rcu() shrinker!\n"); +} + +void __init rcu_init(void) +{ + int cpu; + + rcu_early_boot_tests(); + + kfree_rcu_batch_init(); + rcu_bootup_announce(); + rcu_init_geometry(); + rcu_init_one(); + if (dump_tree) + rcu_dump_rcu_node_tree(); + if (use_softirq) + open_softirq(RCU_SOFTIRQ, rcu_core_si); + + /* + * 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); + srcu_init(); + + /* Fill in default value for rcutree.qovld boot parameter. */ + /* -After- the rcu_node ->lock fields are initialized! */ + if (qovld < 0) + qovld_calc = DEFAULT_RCU_QOVLD_MULT * qhimark; + else + qovld_calc = qovld; +} + +#include "tree_stall.h" +#include "tree_exp.h" +#include "tree_plugin.h" |