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Diffstat (limited to 'kernel/rcu/tree.h')
| -rw-r--r-- | kernel/rcu/tree.h | 490 |
1 files changed, 490 insertions, 0 deletions
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h new file mode 100644 index 000000000..7b702220d --- /dev/null +++ b/kernel/rcu/tree.h @@ -0,0 +1,490 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Read-Copy Update mechanism for mutual exclusion (tree-based version) + * Internal non-public definitions. + * + * Copyright IBM Corporation, 2008 + * + * Author: Ingo Molnar <mingo@elte.hu> + * Paul E. McKenney <paulmck@linux.ibm.com> + */ + +#include <linux/cache.h> +#include <linux/kthread.h> +#include <linux/spinlock.h> +#include <linux/rtmutex.h> +#include <linux/threads.h> +#include <linux/cpumask.h> +#include <linux/seqlock.h> +#include <linux/swait.h> +#include <linux/rcu_node_tree.h> + +#include "rcu_segcblist.h" + +/* Communicate arguments to a workqueue handler. */ +struct rcu_exp_work { + unsigned long rew_s; +#ifdef CONFIG_RCU_EXP_KTHREAD + struct kthread_work rew_work; +#else + struct work_struct rew_work; +#endif /* CONFIG_RCU_EXP_KTHREAD */ +}; + +/* RCU's kthread states for tracing. */ +#define RCU_KTHREAD_STOPPED 0 +#define RCU_KTHREAD_RUNNING 1 +#define RCU_KTHREAD_WAITING 2 +#define RCU_KTHREAD_OFFCPU 3 +#define RCU_KTHREAD_YIELDING 4 +#define RCU_KTHREAD_MAX 4 + +/* + * Definition for node within the RCU grace-period-detection hierarchy. + */ +struct rcu_node { + raw_spinlock_t __private lock; /* Root rcu_node's lock protects */ + /* some rcu_state fields as well as */ + /* following. */ + unsigned long gp_seq; /* Track rsp->gp_seq. */ + unsigned long gp_seq_needed; /* Track furthest future GP request. */ + unsigned long completedqs; /* All QSes done for this node. */ + unsigned long qsmask; /* CPUs or groups that need to switch in */ + /* order for current grace period to proceed.*/ + /* In leaf rcu_node, each bit corresponds to */ + /* an rcu_data structure, otherwise, each */ + /* bit corresponds to a child rcu_node */ + /* structure. */ + unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */ + unsigned long qsmaskinit; + /* Per-GP initial value for qsmask. */ + /* Initialized from ->qsmaskinitnext at the */ + /* beginning of each grace period. */ + unsigned long qsmaskinitnext; + unsigned long expmask; /* CPUs or groups that need to check in */ + /* to allow the current expedited GP */ + /* to complete. */ + unsigned long expmaskinit; + /* Per-GP initial values for expmask. */ + /* Initialized from ->expmaskinitnext at the */ + /* beginning of each expedited GP. */ + unsigned long expmaskinitnext; + /* Online CPUs for next expedited GP. */ + /* Any CPU that has ever been online will */ + /* have its bit set. */ + unsigned long cbovldmask; + /* CPUs experiencing callback overload. */ + unsigned long ffmask; /* Fully functional CPUs. */ + unsigned long grpmask; /* Mask to apply to parent qsmask. */ + /* Only one bit will be set in this mask. */ + int grplo; /* lowest-numbered CPU here. */ + int grphi; /* highest-numbered CPU here. */ + u8 grpnum; /* group number for next level up. */ + u8 level; /* root is at level 0. */ + bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */ + /* exit RCU read-side critical sections */ + /* before propagating offline up the */ + /* rcu_node tree? */ + struct rcu_node *parent; + struct list_head blkd_tasks; + /* Tasks blocked in RCU read-side critical */ + /* section. Tasks are placed at the head */ + /* of this list and age towards the tail. */ + struct list_head *gp_tasks; + /* Pointer to the first task blocking the */ + /* current grace period, or NULL if there */ + /* is no such task. */ + struct list_head *exp_tasks; + /* Pointer to the first task blocking the */ + /* current expedited grace period, or NULL */ + /* if there is no such task. If there */ + /* is no current expedited grace period, */ + /* then there can cannot be any such task. */ + struct list_head *boost_tasks; + /* Pointer to first task that needs to be */ + /* priority boosted, or NULL if no priority */ + /* boosting is needed for this rcu_node */ + /* structure. If there are no tasks */ + /* queued on this rcu_node structure that */ + /* are blocking the current grace period, */ + /* there can be no such task. */ + struct rt_mutex boost_mtx; + /* Used only for the priority-boosting */ + /* side effect, not as a lock. */ + unsigned long boost_time; + /* When to start boosting (jiffies). */ + struct mutex boost_kthread_mutex; + /* Exclusion for thread spawning and affinity */ + /* manipulation. */ + struct task_struct *boost_kthread_task; + /* kthread that takes care of priority */ + /* boosting for this rcu_node structure. */ + unsigned int boost_kthread_status; + /* State of boost_kthread_task for tracing. */ + unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */ +#ifdef CONFIG_RCU_NOCB_CPU + struct swait_queue_head nocb_gp_wq[2]; + /* Place for rcu_nocb_kthread() to wait GP. */ +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ + raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp; + + spinlock_t exp_lock ____cacheline_internodealigned_in_smp; + unsigned long exp_seq_rq; + wait_queue_head_t exp_wq[4]; + struct rcu_exp_work rew; + bool exp_need_flush; /* Need to flush workitem? */ + raw_spinlock_t exp_poll_lock; + /* Lock and data for polled expedited grace periods. */ + unsigned long exp_seq_poll_rq; + struct work_struct exp_poll_wq; +} ____cacheline_internodealigned_in_smp; + +/* + * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and + * are indexed relative to this interval rather than the global CPU ID space. + * This generates the bit for a CPU in node-local masks. + */ +#define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo)) + +/* + * Union to allow "aggregate OR" operation on the need for a quiescent + * state by the normal and expedited grace periods. + */ +union rcu_noqs { + struct { + u8 norm; + u8 exp; + } b; /* Bits. */ + u16 s; /* Set of bits, aggregate OR here. */ +}; + +/* Per-CPU data for read-copy update. */ +struct rcu_data { + /* 1) quiescent-state and grace-period handling : */ + unsigned long gp_seq; /* Track rsp->gp_seq counter. */ + unsigned long gp_seq_needed; /* Track furthest future GP request. */ + union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */ + bool core_needs_qs; /* Core waits for quiescent state. */ + bool beenonline; /* CPU online at least once. */ + bool gpwrap; /* Possible ->gp_seq wrap. */ + bool cpu_started; /* RCU watching this onlining CPU. */ + struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ + unsigned long grpmask; /* Mask to apply to leaf qsmask. */ + unsigned long ticks_this_gp; /* The number of scheduling-clock */ + /* ticks this CPU has handled */ + /* during and after the last grace */ + /* period it is aware of. */ + struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */ + bool defer_qs_iw_pending; /* Scheduler attention pending? */ + struct work_struct strict_work; /* Schedule readers for strict GPs. */ + + /* 2) batch handling */ + struct rcu_segcblist cblist; /* Segmented callback list, with */ + /* different callbacks waiting for */ + /* different grace periods. */ + long qlen_last_fqs_check; + /* qlen at last check for QS forcing */ + unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */ + unsigned long n_force_qs_snap; + /* did other CPU force QS recently? */ + long blimit; /* Upper limit on a processed batch */ + + /* 3) dynticks interface. */ + int dynticks_snap; /* Per-GP tracking for dynticks. */ + bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */ + bool rcu_urgent_qs; /* GP old need light quiescent state. */ + bool rcu_forced_tick; /* Forced tick to provide QS. */ + bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */ + + /* 4) rcu_barrier(), OOM callbacks, and expediting. */ + unsigned long barrier_seq_snap; /* Snap of rcu_state.barrier_sequence. */ + struct rcu_head barrier_head; + int exp_dynticks_snap; /* Double-check need for IPI. */ + + /* 5) Callback offloading. */ +#ifdef CONFIG_RCU_NOCB_CPU + struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */ + struct swait_queue_head nocb_state_wq; /* For offloading state changes */ + struct task_struct *nocb_gp_kthread; + raw_spinlock_t nocb_lock; /* Guard following pair of fields. */ + atomic_t nocb_lock_contended; /* Contention experienced. */ + int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ + struct timer_list nocb_timer; /* Enforce finite deferral. */ + unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */ + struct mutex nocb_gp_kthread_mutex; /* Exclusion for nocb gp kthread */ + /* spawning */ + + /* The following fields are used by call_rcu, hence own cacheline. */ + raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp; + struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */ + unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */ + unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */ + int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */ + + /* The following fields are used by GP kthread, hence own cacheline. */ + raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp; + u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */ + u8 nocb_gp_bypass; /* Found a bypass on last scan? */ + u8 nocb_gp_gp; /* GP to wait for on last scan? */ + unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */ + unsigned long nocb_gp_loops; /* # passes through wait code. */ + struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */ + bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */ + struct task_struct *nocb_cb_kthread; + struct list_head nocb_head_rdp; /* + * Head of rcu_data list in wakeup chain, + * if rdp_gp. + */ + struct list_head nocb_entry_rdp; /* rcu_data node in wakeup chain. */ + struct rcu_data *nocb_toggling_rdp; /* rdp queued for (de-)offloading */ + + /* The following fields are used by CB kthread, hence new cacheline. */ + struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp; + /* GP rdp takes GP-end wakeups. */ +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ + + /* 6) RCU priority boosting. */ + struct task_struct *rcu_cpu_kthread_task; + /* rcuc per-CPU kthread or NULL. */ + unsigned int rcu_cpu_kthread_status; + char rcu_cpu_has_work; + unsigned long rcuc_activity; + + /* 7) Diagnostic data, including RCU CPU stall warnings. */ + unsigned int softirq_snap; /* Snapshot of softirq activity. */ + /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */ + struct irq_work rcu_iw; /* Check for non-irq activity. */ + bool rcu_iw_pending; /* Is ->rcu_iw pending? */ + unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */ + unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */ + short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */ + unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */ + short rcu_onl_gp_flags; /* ->gp_flags at last online. */ + unsigned long last_fqs_resched; /* Time of last rcu_resched(). */ + unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */ + + int cpu; +}; + +/* Values for nocb_defer_wakeup field in struct rcu_data. */ +#define RCU_NOCB_WAKE_NOT 0 +#define RCU_NOCB_WAKE_BYPASS 1 +#define RCU_NOCB_WAKE 2 +#define RCU_NOCB_WAKE_FORCE 3 + +#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) + /* For jiffies_till_first_fqs and */ + /* and jiffies_till_next_fqs. */ + +#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */ + /* delay between bouts of */ + /* quiescent-state forcing. */ + +#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */ + /* at least one scheduling clock */ + /* irq before ratting on them. */ + +#define rcu_wait(cond) \ +do { \ + for (;;) { \ + set_current_state(TASK_INTERRUPTIBLE); \ + if (cond) \ + break; \ + schedule(); \ + } \ + __set_current_state(TASK_RUNNING); \ +} while (0) + +/* + * RCU global state, including node hierarchy. This hierarchy is + * represented in "heap" form in a dense array. The root (first level) + * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second + * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), + * and the third level in ->node[m+1] and following (->node[m+1] referenced + * by ->level[2]). The number of levels is determined by the number of + * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" + * consisting of a single rcu_node. + */ +struct rcu_state { + struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ + struct rcu_node *level[RCU_NUM_LVLS + 1]; + /* Hierarchy levels (+1 to */ + /* shut bogus gcc warning) */ + int ncpus; /* # CPUs seen so far. */ + int n_online_cpus; /* # CPUs online for RCU. */ + + /* The following fields are guarded by the root rcu_node's lock. */ + + unsigned long gp_seq ____cacheline_internodealigned_in_smp; + /* Grace-period sequence #. */ + unsigned long gp_max; /* Maximum GP duration in */ + /* jiffies. */ + struct task_struct *gp_kthread; /* Task for grace periods. */ + struct swait_queue_head gp_wq; /* Where GP task waits. */ + short gp_flags; /* Commands for GP task. */ + short gp_state; /* GP kthread sleep state. */ + unsigned long gp_wake_time; /* Last GP kthread wake. */ + unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */ + unsigned long gp_seq_polled; /* GP seq for polled API. */ + unsigned long gp_seq_polled_snap; /* ->gp_seq_polled at normal GP start. */ + unsigned long gp_seq_polled_exp_snap; /* ->gp_seq_polled at expedited GP start. */ + + /* End of fields guarded by root rcu_node's lock. */ + + struct mutex barrier_mutex; /* Guards barrier fields. */ + atomic_t barrier_cpu_count; /* # CPUs waiting on. */ + struct completion barrier_completion; /* Wake at barrier end. */ + unsigned long barrier_sequence; /* ++ at start and end of */ + /* rcu_barrier(). */ + /* End of fields guarded by barrier_mutex. */ + + raw_spinlock_t barrier_lock; /* Protects ->barrier_seq_snap. */ + + struct mutex exp_mutex; /* Serialize expedited GP. */ + struct mutex exp_wake_mutex; /* Serialize wakeup. */ + unsigned long expedited_sequence; /* Take a ticket. */ + atomic_t expedited_need_qs; /* # CPUs left to check in. */ + struct swait_queue_head expedited_wq; /* Wait for check-ins. */ + int ncpus_snap; /* # CPUs seen last time. */ + u8 cbovld; /* Callback overload now? */ + u8 cbovldnext; /* ^ ^ next time? */ + + unsigned long jiffies_force_qs; /* Time at which to invoke */ + /* force_quiescent_state(). */ + unsigned long jiffies_kick_kthreads; /* Time at which to kick */ + /* kthreads, if configured. */ + unsigned long n_force_qs; /* Number of calls to */ + /* force_quiescent_state(). */ + unsigned long gp_start; /* Time at which GP started, */ + /* but in jiffies. */ + unsigned long gp_end; /* Time last GP ended, again */ + /* in jiffies. */ + unsigned long gp_activity; /* Time of last GP kthread */ + /* activity in jiffies. */ + unsigned long gp_req_activity; /* Time of last GP request */ + /* in jiffies. */ + unsigned long jiffies_stall; /* Time at which to check */ + /* for CPU stalls. */ + int nr_fqs_jiffies_stall; /* Number of fqs loops after + * which read jiffies and set + * jiffies_stall. Stall + * warnings disabled if !0. */ + unsigned long jiffies_resched; /* Time at which to resched */ + /* a reluctant CPU. */ + unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */ + /* GP start. */ + const char *name; /* Name of structure. */ + char abbr; /* Abbreviated name. */ + + arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp; + /* Synchronize offline with */ + /* GP pre-initialization. */ + int nocb_is_setup; /* nocb is setup from boot */ +}; + +/* Values for rcu_state structure's gp_flags field. */ +#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */ +#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */ +#define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */ + +/* Values for rcu_state structure's gp_state field. */ +#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */ +#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */ +#define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */ +#define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */ +#define RCU_GP_INIT 4 /* Grace-period initialization. */ +#define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */ +#define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */ +#define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */ +#define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */ + +/* + * In order to export the rcu_state name to the tracing tools, it + * needs to be added in the __tracepoint_string section. + * This requires defining a separate variable tp_<sname>_varname + * that points to the string being used, and this will allow + * the tracing userspace tools to be able to decipher the string + * address to the matching string. + */ +#ifdef CONFIG_PREEMPT_RCU +#define RCU_ABBR 'p' +#define RCU_NAME_RAW "rcu_preempt" +#else /* #ifdef CONFIG_PREEMPT_RCU */ +#define RCU_ABBR 's' +#define RCU_NAME_RAW "rcu_sched" +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ +#ifndef CONFIG_TRACING +#define RCU_NAME RCU_NAME_RAW +#else /* #ifdef CONFIG_TRACING */ +static char rcu_name[] = RCU_NAME_RAW; +static const char *tp_rcu_varname __used __tracepoint_string = rcu_name; +#define RCU_NAME rcu_name +#endif /* #else #ifdef CONFIG_TRACING */ + +/* Forward declarations for tree_plugin.h */ +static void rcu_bootup_announce(void); +static void rcu_qs(void); +static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); +#ifdef CONFIG_HOTPLUG_CPU +static bool rcu_preempt_has_tasks(struct rcu_node *rnp); +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ +static int rcu_print_task_exp_stall(struct rcu_node *rnp); +static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); +static void rcu_flavor_sched_clock_irq(int user); +static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck); +static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); +static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); +static bool rcu_is_callbacks_kthread(struct rcu_data *rdp); +static void rcu_cpu_kthread_setup(unsigned int cpu); +static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp); +static bool rcu_preempt_has_tasks(struct rcu_node *rnp); +static bool rcu_preempt_need_deferred_qs(struct task_struct *t); +static void zero_cpu_stall_ticks(struct rcu_data *rdp); +static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp); +static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq); +static void rcu_init_one_nocb(struct rcu_node *rnp); +static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp, + unsigned long j); +static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, + bool *was_alldone, unsigned long flags); +static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, + unsigned long flags); +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level); +static bool do_nocb_deferred_wakeup(struct rcu_data *rdp); +static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); +static void rcu_spawn_cpu_nocb_kthread(int cpu); +static void show_rcu_nocb_state(struct rcu_data *rdp); +static void rcu_nocb_lock(struct rcu_data *rdp); +static void rcu_nocb_unlock(struct rcu_data *rdp); +static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp, + unsigned long flags); +static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp); +#ifdef CONFIG_RCU_NOCB_CPU +static void __init rcu_organize_nocb_kthreads(void); + +/* + * Disable IRQs before checking offloaded state so that local + * locking is safe against concurrent de-offloading. + */ +#define rcu_nocb_lock_irqsave(rdp, flags) \ +do { \ + local_irq_save(flags); \ + if (rcu_segcblist_is_offloaded(&(rdp)->cblist)) \ + raw_spin_lock(&(rdp)->nocb_lock); \ +} while (0) +#else /* #ifdef CONFIG_RCU_NOCB_CPU */ +#define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags) +#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ + +static void rcu_bind_gp_kthread(void); +static bool rcu_nohz_full_cpu(void); + +/* Forward declarations for tree_stall.h */ +static void record_gp_stall_check_time(void); +static void rcu_iw_handler(struct irq_work *iwp); +static void check_cpu_stall(struct rcu_data *rdp); +static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, + const unsigned long gpssdelay); + +/* Forward declarations for tree_exp.h. */ +static void sync_rcu_do_polled_gp(struct work_struct *wp); |