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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253// SPDX-License-Identifier: GPL-2.0+/* * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. * * Copyright IBM Corporation, 2008 * * Author: Paul E. McKenney <paulmck@linux.ibm.com> * * For detailed explanation of Read-Copy Update mechanism see - * Documentation/RCU */#include <linux/completion.h>#include <linux/interrupt.h>#include <linux/notifier.h>#include <linux/rcupdate_wait.h>#include <linux/kernel.h>#include <linux/export.h>#include <linux/mutex.h>#include <linux/sched.h>#include <linux/types.h>#include <linux/init.h>#include <linux/time.h>#include <linux/cpu.h>#include <linux/prefetch.h>#include <linux/slab.h>#include <linux/mm.h>
#include "rcu.h"
/* Global control variables for rcupdate callback mechanism. */struct rcu_ctrlblk { struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */ struct rcu_head **donetail; /* ->next pointer of last "done" CB. */ struct rcu_head **curtail; /* ->next pointer of last CB. */ unsigned long gp_seq; /* Grace-period counter. */};
/* Definition for rcupdate control block. */static struct rcu_ctrlblk rcu_ctrlblk = { .donetail = &rcu_ctrlblk.rcucblist, .curtail = &rcu_ctrlblk.rcucblist, .gp_seq = 0 - 300UL,};
void rcu_barrier(void){ wait_rcu_gp(call_rcu_hurry);}EXPORT_SYMBOL(rcu_barrier);
/* Record an rcu quiescent state. */void rcu_qs(void){ unsigned long flags;
local_irq_save(flags); if (rcu_ctrlblk.donetail != rcu_ctrlblk.curtail) { rcu_ctrlblk.donetail = rcu_ctrlblk.curtail; raise_softirq_irqoff(RCU_SOFTIRQ); } WRITE_ONCE(rcu_ctrlblk.gp_seq, rcu_ctrlblk.gp_seq + 2); local_irq_restore(flags);}
/* * Check to see if the scheduling-clock interrupt came from an extended * quiescent state, and, if so, tell RCU about it. This function must * be called from hardirq context. It is normally called from the * scheduling-clock interrupt. */void rcu_sched_clock_irq(int user){ if (user) rcu_qs(); else if (rcu_ctrlblk.donetail != rcu_ctrlblk.curtail) set_need_resched_current();}
/* * Reclaim the specified callback, either by invoking it for non-kfree cases or * freeing it directly (for kfree). Return true if kfreeing, false otherwise. */static inline bool rcu_reclaim_tiny(struct rcu_head *head){ rcu_callback_t f;
rcu_lock_acquire(&rcu_callback_map);
trace_rcu_invoke_callback("", head); f = head->func; debug_rcu_head_callback(head); WRITE_ONCE(head->func, (rcu_callback_t)0L); f(head); rcu_lock_release(&rcu_callback_map); return false;}
/* Invoke the RCU callbacks whose grace period has elapsed. */static __latent_entropy void rcu_process_callbacks(void){ struct rcu_head *next, *list; unsigned long flags;
/* Move the ready-to-invoke callbacks to a local list. */ local_irq_save(flags); if (rcu_ctrlblk.donetail == &rcu_ctrlblk.rcucblist) { /* No callbacks ready, so just leave. */ local_irq_restore(flags); return; } list = rcu_ctrlblk.rcucblist; rcu_ctrlblk.rcucblist = *rcu_ctrlblk.donetail; *rcu_ctrlblk.donetail = NULL; if (rcu_ctrlblk.curtail == rcu_ctrlblk.donetail) rcu_ctrlblk.curtail = &rcu_ctrlblk.rcucblist; rcu_ctrlblk.donetail = &rcu_ctrlblk.rcucblist; local_irq_restore(flags);
/* Invoke the callbacks on the local list. */ while (list) { next = list->next; prefetch(next); debug_rcu_head_unqueue(list); rcu_reclaim_tiny(list); list = next; }}
/* * Wait for a grace period to elapse. But it is illegal to invoke * synchronize_rcu() from within an RCU read-side critical section. * Therefore, any legal call to synchronize_rcu() is a quiescent state, * and so on a UP system, synchronize_rcu() need do nothing, other than * let the polled APIs know that another grace period elapsed. * * (But Lai Jiangshan points out the benefits of doing might_sleep() * to reduce latency.) * * Cool, huh? (Due to Josh Triplett.) */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"); preempt_disable(); WRITE_ONCE(rcu_ctrlblk.gp_seq, rcu_ctrlblk.gp_seq + 2); preempt_enable();}EXPORT_SYMBOL_GPL(synchronize_rcu);
/* * Post an RCU callback to be invoked after the end of an RCU grace * period. But since we have but one CPU, that would be after any * quiescent state. */void call_rcu(struct rcu_head *head, rcu_callback_t func){ static atomic_t doublefrees; unsigned long flags;
if (debug_rcu_head_queue(head)) { if (atomic_inc_return(&doublefrees) < 4) { pr_err("%s(): Double-freed CB %p->%pS()!!! ", __func__, head, head->func); mem_dump_obj(head); } return; }
head->func = func; head->next = NULL;
local_irq_save(flags); *rcu_ctrlblk.curtail = head; rcu_ctrlblk.curtail = &head->next; local_irq_restore(flags);
if (unlikely(is_idle_task(current))) { /* force scheduling for rcu_qs() */ resched_cpu(0); }}EXPORT_SYMBOL_GPL(call_rcu);
/* * Store a grace-period-counter "cookie". For more information, * see the Tree RCU header comment. */void get_completed_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp){ rgosp->rgos_norm = RCU_GET_STATE_COMPLETED;}EXPORT_SYMBOL_GPL(get_completed_synchronize_rcu_full);
/* * Return a grace-period-counter "cookie". For more information, * see the Tree RCU header comment. */unsigned long get_state_synchronize_rcu(void){ return READ_ONCE(rcu_ctrlblk.gp_seq);}EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
/* * Return a grace-period-counter "cookie" and ensure that a future grace * period completes. For more information, see the Tree RCU header comment. */unsigned long start_poll_synchronize_rcu(void){ unsigned long gp_seq = get_state_synchronize_rcu();
if (unlikely(is_idle_task(current))) { /* force scheduling for rcu_qs() */ resched_cpu(0); } return gp_seq;}EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu);
/* * Return true if the grace period corresponding to oldstate has completed * and false otherwise. For more information, see the Tree RCU header * comment. */bool poll_state_synchronize_rcu(unsigned long oldstate){ return oldstate == RCU_GET_STATE_COMPLETED || READ_ONCE(rcu_ctrlblk.gp_seq) != oldstate;}EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu);
#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST)unsigned long long rcutorture_gather_gp_seqs(void){ return READ_ONCE(rcu_ctrlblk.gp_seq) & 0xffffULL;}EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len){ snprintf(cp, len, "g%04llx", seqs & 0xffffULL);}EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);#endif
void __init rcu_init(void){ open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); rcu_early_boot_tests(); tasks_cblist_init_generic();}