/* * Read-Copy Update mechanism for mutual exclusion * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, you can access it online at * http://www.gnu.org/licenses/gpl-2.0.html. * * Copyright IBM Corporation, 2001 * * Authors: Dipankar Sarma <dipankar@in.ibm.com> * Manfred Spraul <manfred@colorfullife.com> * * Based on the original work by Paul McKenney <paulmck@us.ibm.com> * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * Papers: * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) * * For detailed explanation of Read-Copy Update mechanism see - * http://lse.sourceforge.net/locking/rcupdate.html * */#include <linux/types.h>#include <linux/kernel.h>#include <linux/init.h>#include <linux/spinlock.h>#include <linux/smp.h>#include <linux/interrupt.h>#include <linux/sched/signal.h>#include <linux/sched/debug.h>#include <linux/atomic.h>#include <linux/bitops.h>#include <linux/percpu.h>#include <linux/notifier.h>#include <linux/cpu.h>#include <linux/mutex.h>#include <linux/export.h>#include <linux/hardirq.h>#include <linux/delay.h>#include <linux/moduleparam.h>#include <linux/kthread.h>#include <linux/tick.h>#include <linux/rcupdate_wait.h> #define CREATE_TRACE_POINTS #include "rcu.h" #ifdef MODULE_PARAM_PREFIX#undef MODULE_PARAM_PREFIX#endif#define MODULE_PARAM_PREFIX "rcupdate." #ifndef CONFIG_TINY_RCUextern int rcu_expedited; /* from sysctl */module_param(rcu_expedited, int, 0);extern int rcu_normal; /* from sysctl */module_param(rcu_normal, int, 0);static int rcu_normal_after_boot;module_param(rcu_normal_after_boot, int, 0);#endif /* #ifndef CONFIG_TINY_RCU */ #ifdef CONFIG_DEBUG_LOCK_ALLOC/** * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? * * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an * RCU-sched read-side critical section. In absence of * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side * critical section unless it can prove otherwise. Note that disabling * of preemption (including disabling irqs) counts as an RCU-sched * read-side critical section. This is useful for debug checks in functions * that required that they be called within an RCU-sched read-side * critical section. * * Check debug_lockdep_rcu_enabled() to prevent false positives during boot * and while lockdep is disabled. * * Note that if the CPU is in the idle loop from an RCU point of * view (ie: that we are in the section between rcu_idle_enter() and * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs * that are in such a section, considering these as in extended quiescent * state, so such a CPU is effectively never in an RCU read-side critical * section regardless of what RCU primitives it invokes. This state of * affairs is required --- we need to keep an RCU-free window in idle * where the CPU may possibly enter into low power mode. This way we can * notice an extended quiescent state to other CPUs that started a grace * period. Otherwise we would delay any grace period as long as we run in * the idle task. * * Similarly, we avoid claiming an SRCU read lock held if the current * CPU is offline. */int rcu_read_lock_sched_held(void){ int lockdep_opinion = 0; if (!debug_lockdep_rcu_enabled()) return 1; if (!rcu_is_watching()) return 0; if (!rcu_lockdep_current_cpu_online()) return 0; if (debug_locks) lockdep_opinion = lock_is_held(&rcu_sched_lock_map); return lockdep_opinion || !preemptible();}EXPORT_SYMBOL(rcu_read_lock_sched_held);#endif #ifndef CONFIG_TINY_RCU /* * Should expedited grace-period primitives always fall back to their * non-expedited counterparts? Intended for use within RCU. Note * that if the user specifies both rcu_expedited and rcu_normal, then * rcu_normal wins. (Except during the time period during boot from * when the first task is spawned until the rcu_set_runtime_mode() * core_initcall() is invoked, at which point everything is expedited.) */bool rcu_gp_is_normal(void){ return READ_ONCE(rcu_normal) && rcu_scheduler_active != RCU_SCHEDULER_INIT;}EXPORT_SYMBOL_GPL(rcu_gp_is_normal); static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1); /* * Should normal grace-period primitives be expedited? Intended for * use within RCU. Note that this function takes the rcu_expedited * sysfs/boot variable and rcu_scheduler_active into account as well * as the rcu_expedite_gp() nesting. So looping on rcu_unexpedite_gp() * until rcu_gp_is_expedited() returns false is a -really- bad idea. */bool rcu_gp_is_expedited(void){ return rcu_expedited || atomic_read(&rcu_expedited_nesting) || rcu_scheduler_active == RCU_SCHEDULER_INIT;}EXPORT_SYMBOL_GPL(rcu_gp_is_expedited); /** * rcu_expedite_gp - Expedite future RCU grace periods * * After a call to this function, future calls to synchronize_rcu() and * friends act as the corresponding synchronize_rcu_expedited() function * had instead been called. */void rcu_expedite_gp(void){ atomic_inc(&rcu_expedited_nesting);}EXPORT_SYMBOL_GPL(rcu_expedite_gp); /** * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation * * Undo a prior call to rcu_expedite_gp(). If all prior calls to * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(), * and if the rcu_expedited sysfs/boot parameter is not set, then all * subsequent calls to synchronize_rcu() and friends will return to * their normal non-expedited behavior. */void rcu_unexpedite_gp(void){ atomic_dec(&rcu_expedited_nesting);}EXPORT_SYMBOL_GPL(rcu_unexpedite_gp); /* * Inform RCU of the end of the in-kernel boot sequence. */void rcu_end_inkernel_boot(void){ rcu_unexpedite_gp(); if (rcu_normal_after_boot) WRITE_ONCE(rcu_normal, 1);} #endif /* #ifndef CONFIG_TINY_RCU */ /* * Test each non-SRCU synchronous grace-period wait API. This is * useful just after a change in mode for these primitives, and * during early boot. */void rcu_test_sync_prims(void){ if (!IS_ENABLED(CONFIG_PROVE_RCU)) return; synchronize_rcu(); synchronize_rcu_bh(); synchronize_sched(); synchronize_rcu_expedited(); synchronize_rcu_bh_expedited(); synchronize_sched_expedited();} #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) /* * Switch to run-time mode once RCU has fully initialized. */static int __init rcu_set_runtime_mode(void){ rcu_test_sync_prims(); rcu_scheduler_active = RCU_SCHEDULER_RUNNING; rcu_test_sync_prims(); return 0;}core_initcall(rcu_set_runtime_mode); #endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */ #ifdef CONFIG_PREEMPT_RCU /* * Preemptible RCU implementation for rcu_read_lock(). * Just increment ->rcu_read_lock_nesting, shared state will be updated * if we block. */void __rcu_read_lock(void){ current->rcu_read_lock_nesting++; barrier(); /* critical section after entry code. */}EXPORT_SYMBOL_GPL(__rcu_read_lock); /* * Preemptible RCU implementation for rcu_read_unlock(). * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then * invoke rcu_read_unlock_special() to clean up after a context switch * in an RCU read-side critical section and other special cases. */void __rcu_read_unlock(void){ struct task_struct *t = current; if (t->rcu_read_lock_nesting != 1) { --t->rcu_read_lock_nesting; } else { barrier(); /* critical section before exit code. */ t->rcu_read_lock_nesting = INT_MIN; barrier(); /* assign before ->rcu_read_unlock_special load */ if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s))) rcu_read_unlock_special(t); barrier(); /* ->rcu_read_unlock_special load before assign */ t->rcu_read_lock_nesting = 0; }#ifdef CONFIG_PROVE_LOCKING { int rrln = READ_ONCE(t->rcu_read_lock_nesting); WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2); }#endif /* #ifdef CONFIG_PROVE_LOCKING */}EXPORT_SYMBOL_GPL(__rcu_read_unlock); #endif /* #ifdef CONFIG_PREEMPT_RCU */ #ifdef CONFIG_DEBUG_LOCK_ALLOCstatic struct lock_class_key rcu_lock_key;struct lockdep_map rcu_lock_map = STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);EXPORT_SYMBOL_GPL(rcu_lock_map); static struct lock_class_key rcu_bh_lock_key;struct lockdep_map rcu_bh_lock_map = STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);EXPORT_SYMBOL_GPL(rcu_bh_lock_map); static struct lock_class_key rcu_sched_lock_key;struct lockdep_map rcu_sched_lock_map = STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);EXPORT_SYMBOL_GPL(rcu_sched_lock_map); static struct lock_class_key rcu_callback_key;struct lockdep_map rcu_callback_map = STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key);EXPORT_SYMBOL_GPL(rcu_callback_map); int notrace debug_lockdep_rcu_enabled(void){ return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && debug_locks && current->lockdep_recursion == 0;}EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); /** * rcu_read_lock_held() - might we be in RCU read-side critical section? * * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, * this assumes we are in an RCU read-side critical section unless it can * prove otherwise. This is useful for debug checks in functions that * require that they be called within an RCU read-side critical section. * * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot * and while lockdep is disabled. * * Note that rcu_read_lock() and the matching rcu_read_unlock() must * occur in the same context, for example, it is illegal to invoke * rcu_read_unlock() in process context if the matching rcu_read_lock() * was invoked from within an irq handler. * * Note that rcu_read_lock() is disallowed if the CPU is either idle or * offline from an RCU perspective, so check for those as well. */int rcu_read_lock_held(void){ if (!debug_lockdep_rcu_enabled()) return 1; if (!rcu_is_watching()) return 0; if (!rcu_lockdep_current_cpu_online()) return 0; return lock_is_held(&rcu_lock_map);}EXPORT_SYMBOL_GPL(rcu_read_lock_held); /** * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? * * Check for bottom half being disabled, which covers both the * CONFIG_PROVE_RCU and not cases. Note that if someone uses * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) * will show the situation. This is useful for debug checks in functions * that require that they be called within an RCU read-side critical * section. * * Check debug_lockdep_rcu_enabled() to prevent false positives during boot. * * Note that rcu_read_lock() is disallowed if the CPU is either idle or * offline from an RCU perspective, so check for those as well. */int rcu_read_lock_bh_held(void){ if (!debug_lockdep_rcu_enabled()) return 1; if (!rcu_is_watching()) return 0; if (!rcu_lockdep_current_cpu_online()) return 0; return in_softirq() || irqs_disabled();}EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ /** * wakeme_after_rcu() - Callback function to awaken a task after grace period * @head: Pointer to rcu_head member within rcu_synchronize structure * * Awaken the corresponding task now that a grace period has elapsed. */void wakeme_after_rcu(struct rcu_head *head){ struct rcu_synchronize *rcu; rcu = container_of(head, struct rcu_synchronize, head); complete(&rcu->completion);}EXPORT_SYMBOL_GPL(wakeme_after_rcu); void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, struct rcu_synchronize *rs_array){ int i; int j; /* Initialize and register callbacks for each flavor specified. */ for (i = 0; i < n; i++) { if (checktiny && (crcu_array[i] == call_rcu || crcu_array[i] == call_rcu_bh)) { might_sleep(); continue; } init_rcu_head_on_stack(&rs_array[i].head); init_completion(&rs_array[i].completion); for (j = 0; j < i; j++) if (crcu_array[j] == crcu_array[i]) break; if (j == i) (crcu_array[i])(&rs_array[i].head, wakeme_after_rcu); } /* Wait for all callbacks to be invoked. */ for (i = 0; i < n; i++) { if (checktiny && (crcu_array[i] == call_rcu || crcu_array[i] == call_rcu_bh)) continue; for (j = 0; j < i; j++) if (crcu_array[j] == crcu_array[i]) break; if (j == i) wait_for_completion(&rs_array[i].completion); destroy_rcu_head_on_stack(&rs_array[i].head); }}EXPORT_SYMBOL_GPL(__wait_rcu_gp); #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEADvoid init_rcu_head(struct rcu_head *head){ debug_object_init(head, &rcuhead_debug_descr);} void destroy_rcu_head(struct rcu_head *head){ debug_object_free(head, &rcuhead_debug_descr);} static bool rcuhead_is_static_object(void *addr){ return true;} /** * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects * @head: pointer to rcu_head structure to be initialized * * This function informs debugobjects of a new rcu_head structure that * has been allocated as an auto variable on the stack. This function * is not required for rcu_head structures that are statically defined or * that are dynamically allocated on the heap. This function has no * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. */void init_rcu_head_on_stack(struct rcu_head *head){ debug_object_init_on_stack(head, &rcuhead_debug_descr);}EXPORT_SYMBOL_GPL(init_rcu_head_on_stack); /** * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects * @head: pointer to rcu_head structure to be initialized * * This function informs debugobjects that an on-stack rcu_head structure * is about to go out of scope. As with init_rcu_head_on_stack(), this * function is not required for rcu_head structures that are statically * defined or that are dynamically allocated on the heap. Also as with * init_rcu_head_on_stack(), this function has no effect for * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. */void destroy_rcu_head_on_stack(struct rcu_head *head){ debug_object_free(head, &rcuhead_debug_descr);}EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack); struct debug_obj_descr rcuhead_debug_descr = { .name = "rcu_head", .is_static_object = rcuhead_is_static_object,};EXPORT_SYMBOL_GPL(rcuhead_debug_descr);#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, unsigned long secs, unsigned long c_old, unsigned long c){ trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);}EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);#else#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ do { } while (0)#endif #ifdef CONFIG_RCU_STALL_COMMON #ifdef CONFIG_PROVE_RCU#define RCU_STALL_DELAY_DELTA (5 * HZ)#else#define RCU_STALL_DELAY_DELTA 0#endif int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */static int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; module_param(rcu_cpu_stall_suppress, int, 0644);module_param(rcu_cpu_stall_timeout, int, 0644);Lines 1–500 of 1002. 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/* * Read-Copy Update mechanism for mutual exclusion * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, you can access it online at * http://www.gnu.org/licenses/gpl-2.0.html. * * Copyright IBM Corporation, 2001 * * Authors: Dipankar Sarma <dipankar@in.ibm.com> * Manfred Spraul <manfred@colorfullife.com> * * Based on the original work by Paul McKenney <paulmck@us.ibm.com> * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * Papers: * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) * * For detailed explanation of Read-Copy Update mechanism see - * http://lse.sourceforge.net/locking/rcupdate.html * */ #include <linux/types.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/spinlock.h> #include <linux/smp.h> #include <linux/interrupt.h> #include <linux/sched/signal.h> #include <linux/sched/debug.h> #include <linux/atomic.h> #include <linux/bitops.h> #include <linux/percpu.h> #include <linux/notifier.h> #include <linux/cpu.h> #include <linux/mutex.h> #include <linux/export.h> #include <linux/hardirq.h> #include <linux/delay.h> #include <linux/moduleparam.h> #include <linux/kthread.h> #include <linux/tick.h> #include <linux/rcupdate_wait.h> #define CREATE_TRACE_POINTS #include "rcu.h" #ifdef MODULE_PARAM_PREFIX #undef MODULE_PARAM_PREFIX #endif #define MODULE_PARAM_PREFIX "rcupdate." #ifndef CONFIG_TINY_RCU extern int rcu_expedited; /* from sysctl */ module_param(rcu_expedited, int, 0); extern int rcu_normal; /* from sysctl */ module_param(rcu_normal, int, 0); static int rcu_normal_after_boot; module_param(rcu_normal_after_boot, int, 0); #endif /* #ifndef CONFIG_TINY_RCU */ #ifdef CONFIG_DEBUG_LOCK_ALLOC /** * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? * * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an * RCU-sched read-side critical section. In absence of * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side * critical section unless it can prove otherwise. Note that disabling * of preemption (including disabling irqs) counts as an RCU-sched * read-side critical section. This is useful for debug checks in functions * that required that they be called within an RCU-sched read-side * critical section. * * Check debug_lockdep_rcu_enabled() to prevent false positives during boot * and while lockdep is disabled. * * Note that if the CPU is in the idle loop from an RCU point of * view (ie: that we are in the section between rcu_idle_enter() and * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs * that are in such a section, considering these as in extended quiescent * state, so such a CPU is effectively never in an RCU read-side critical * section regardless of what RCU primitives it invokes. This state of * affairs is required --- we need to keep an RCU-free window in idle * where the CPU may possibly enter into low power mode. This way we can * notice an extended quiescent state to other CPUs that started a grace * period. Otherwise we would delay any grace period as long as we run in * the idle task. * * Similarly, we avoid claiming an SRCU read lock held if the current * CPU is offline. */ int rcu_read_lock_sched_held(void) { int lockdep_opinion = 0; if (!debug_lockdep_rcu_enabled()) return 1; if (!rcu_is_watching()) return 0; if (!rcu_lockdep_current_cpu_online()) return 0; if (debug_locks) lockdep_opinion = lock_is_held(&rcu_sched_lock_map); return lockdep_opinion || !preemptible(); } EXPORT_SYMBOL(rcu_read_lock_sched_held); #endif #ifndef CONFIG_TINY_RCU /* * Should expedited grace-period primitives always fall back to their * non-expedited counterparts? Intended for use within RCU. Note * that if the user specifies both rcu_expedited and rcu_normal, then * rcu_normal wins. (Except during the time period during boot from * when the first task is spawned until the rcu_set_runtime_mode() * core_initcall() is invoked, at which point everything is expedited.) */ bool rcu_gp_is_normal(void) { return READ_ONCE(rcu_normal) && rcu_scheduler_active != RCU_SCHEDULER_INIT; } EXPORT_SYMBOL_GPL(rcu_gp_is_normal); static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1); /* * Should normal grace-period primitives be expedited? Intended for * use within RCU. Note that this function takes the rcu_expedited * sysfs/boot variable and rcu_scheduler_active into account as well * as the rcu_expedite_gp() nesting. So looping on rcu_unexpedite_gp() * until rcu_gp_is_expedited() returns false is a -really- bad idea. */ bool rcu_gp_is_expedited(void) { return rcu_expedited || atomic_read(&rcu_expedited_nesting) || rcu_scheduler_active == RCU_SCHEDULER_INIT; } EXPORT_SYMBOL_GPL(rcu_gp_is_expedited); /** * rcu_expedite_gp - Expedite future RCU grace periods * * After a call to this function, future calls to synchronize_rcu() and * friends act as the corresponding synchronize_rcu_expedited() function * had instead been called. */ void rcu_expedite_gp(void) { atomic_inc(&rcu_expedited_nesting); } EXPORT_SYMBOL_GPL(rcu_expedite_gp); /** * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation * * Undo a prior call to rcu_expedite_gp(). If all prior calls to * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(), * and if the rcu_expedited sysfs/boot parameter is not set, then all * subsequent calls to synchronize_rcu() and friends will return to * their normal non-expedited behavior. */ void rcu_unexpedite_gp(void) { atomic_dec(&rcu_expedited_nesting); } EXPORT_SYMBOL_GPL(rcu_unexpedite_gp); /* * Inform RCU of the end of the in-kernel boot sequence. */ void rcu_end_inkernel_boot(void) { rcu_unexpedite_gp(); if (rcu_normal_after_boot) WRITE_ONCE(rcu_normal, 1); } #endif /* #ifndef CONFIG_TINY_RCU */ /* * Test each non-SRCU synchronous grace-period wait API. This is * useful just after a change in mode for these primitives, and * during early boot. */ void rcu_test_sync_prims(void) { if (!IS_ENABLED(CONFIG_PROVE_RCU)) return; synchronize_rcu(); synchronize_rcu_bh(); synchronize_sched(); synchronize_rcu_expedited(); synchronize_rcu_bh_expedited(); synchronize_sched_expedited(); } #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) /* * Switch to run-time mode once RCU has fully initialized. */ static int __init rcu_set_runtime_mode(void) { rcu_test_sync_prims(); rcu_scheduler_active = RCU_SCHEDULER_RUNNING; rcu_test_sync_prims(); return 0; } core_initcall(rcu_set_runtime_mode); #endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */ #ifdef CONFIG_PREEMPT_RCU /* * Preemptible RCU implementation for rcu_read_lock(). * Just increment ->rcu_read_lock_nesting, shared state will be updated * if we block. */ void __rcu_read_lock(void) { current->rcu_read_lock_nesting++; barrier(); /* critical section after entry code. */ } EXPORT_SYMBOL_GPL(__rcu_read_lock); /* * Preemptible RCU implementation for rcu_read_unlock(). * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then * invoke rcu_read_unlock_special() to clean up after a context switch * in an RCU read-side critical section and other special cases. */ void __rcu_read_unlock(void) { struct task_struct *t = current; if (t->rcu_read_lock_nesting != 1) { --t->rcu_read_lock_nesting; } else { barrier(); /* critical section before exit code. */ t->rcu_read_lock_nesting = INT_MIN; barrier(); /* assign before ->rcu_read_unlock_special load */ if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s))) rcu_read_unlock_special(t); barrier(); /* ->rcu_read_unlock_special load before assign */ t->rcu_read_lock_nesting = 0; } #ifdef CONFIG_PROVE_LOCKING { int rrln = READ_ONCE(t->rcu_read_lock_nesting); WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2); } #endif /* #ifdef CONFIG_PROVE_LOCKING */ } EXPORT_SYMBOL_GPL(__rcu_read_unlock); #endif /* #ifdef CONFIG_PREEMPT_RCU */ #ifdef CONFIG_DEBUG_LOCK_ALLOC static struct lock_class_key rcu_lock_key; struct lockdep_map rcu_lock_map = STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); EXPORT_SYMBOL_GPL(rcu_lock_map); static struct lock_class_key rcu_bh_lock_key; struct lockdep_map rcu_bh_lock_map = STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key); EXPORT_SYMBOL_GPL(rcu_bh_lock_map); static struct lock_class_key rcu_sched_lock_key; struct lockdep_map rcu_sched_lock_map = STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key); EXPORT_SYMBOL_GPL(rcu_sched_lock_map); static struct lock_class_key rcu_callback_key; struct lockdep_map rcu_callback_map = STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key); EXPORT_SYMBOL_GPL(rcu_callback_map); int notrace debug_lockdep_rcu_enabled(void) { return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && debug_locks && current->lockdep_recursion == 0; } EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); /** * rcu_read_lock_held() - might we be in RCU read-side critical section? * * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, * this assumes we are in an RCU read-side critical section unless it can * prove otherwise. This is useful for debug checks in functions that * require that they be called within an RCU read-side critical section. * * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot * and while lockdep is disabled. * * Note that rcu_read_lock() and the matching rcu_read_unlock() must * occur in the same context, for example, it is illegal to invoke * rcu_read_unlock() in process context if the matching rcu_read_lock() * was invoked from within an irq handler. * * Note that rcu_read_lock() is disallowed if the CPU is either idle or * offline from an RCU perspective, so check for those as well. */ int rcu_read_lock_held(void) { if (!debug_lockdep_rcu_enabled()) return 1; if (!rcu_is_watching()) return 0; if (!rcu_lockdep_current_cpu_online()) return 0; return lock_is_held(&rcu_lock_map); } EXPORT_SYMBOL_GPL(rcu_read_lock_held); /** * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? * * Check for bottom half being disabled, which covers both the * CONFIG_PROVE_RCU and not cases. Note that if someone uses * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) * will show the situation. This is useful for debug checks in functions * that require that they be called within an RCU read-side critical * section. * * Check debug_lockdep_rcu_enabled() to prevent false positives during boot. * * Note that rcu_read_lock() is disallowed if the CPU is either idle or * offline from an RCU perspective, so check for those as well. */ int rcu_read_lock_bh_held(void) { if (!debug_lockdep_rcu_enabled()) return 1; if (!rcu_is_watching()) return 0; if (!rcu_lockdep_current_cpu_online()) return 0; return in_softirq() || irqs_disabled(); } EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ /** * wakeme_after_rcu() - Callback function to awaken a task after grace period * @head: Pointer to rcu_head member within rcu_synchronize structure * * Awaken the corresponding task now that a grace period has elapsed. */ void wakeme_after_rcu(struct rcu_head *head) { struct rcu_synchronize *rcu; rcu = container_of(head, struct rcu_synchronize, head); complete(&rcu->completion); } EXPORT_SYMBOL_GPL(wakeme_after_rcu); void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, struct rcu_synchronize *rs_array) { int i; int j; /* Initialize and register callbacks for each flavor specified. */ for (i = 0; i < n; i++) { if (checktiny && (crcu_array[i] == call_rcu || crcu_array[i] == call_rcu_bh)) { might_sleep(); continue; } init_rcu_head_on_stack(&rs_array[i].head); init_completion(&rs_array[i].completion); for (j = 0; j < i; j++) if (crcu_array[j] == crcu_array[i]) break; if (j == i) (crcu_array[i])(&rs_array[i].head, wakeme_after_rcu); } /* Wait for all callbacks to be invoked. */ for (i = 0; i < n; i++) { if (checktiny && (crcu_array[i] == call_rcu || crcu_array[i] == call_rcu_bh)) continue; for (j = 0; j < i; j++) if (crcu_array[j] == crcu_array[i]) break; if (j == i) wait_for_completion(&rs_array[i].completion); destroy_rcu_head_on_stack(&rs_array[i].head); } } EXPORT_SYMBOL_GPL(__wait_rcu_gp); #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD void init_rcu_head(struct rcu_head *head) { debug_object_init(head, &rcuhead_debug_descr); } void destroy_rcu_head(struct rcu_head *head) { debug_object_free(head, &rcuhead_debug_descr); } static bool rcuhead_is_static_object(void *addr) { return true; } /** * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects * @head: pointer to rcu_head structure to be initialized * * This function informs debugobjects of a new rcu_head structure that * has been allocated as an auto variable on the stack. This function * is not required for rcu_head structures that are statically defined or * that are dynamically allocated on the heap. This function has no * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. */ void init_rcu_head_on_stack(struct rcu_head *head) { debug_object_init_on_stack(head, &rcuhead_debug_descr); } EXPORT_SYMBOL_GPL(init_rcu_head_on_stack); /** * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects * @head: pointer to rcu_head structure to be initialized * * This function informs debugobjects that an on-stack rcu_head structure * is about to go out of scope. As with init_rcu_head_on_stack(), this * function is not required for rcu_head structures that are statically * defined or that are dynamically allocated on the heap. Also as with * init_rcu_head_on_stack(), this function has no effect for * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. */ void destroy_rcu_head_on_stack(struct rcu_head *head) { debug_object_free(head, &rcuhead_debug_descr); } EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack); struct debug_obj_descr rcuhead_debug_descr = { .name = "rcu_head", .is_static_object = rcuhead_is_static_object, }; EXPORT_SYMBOL_GPL(rcuhead_debug_descr); #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE) void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, unsigned long secs, unsigned long c_old, unsigned long c) { trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c); } EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read); #else #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ do { } while (0) #endif #ifdef CONFIG_RCU_STALL_COMMON #ifdef CONFIG_PROVE_RCU #define RCU_STALL_DELAY_DELTA (5 * HZ) #else #define RCU_STALL_DELAY_DELTA 0 #endif int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ static int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; module_param(rcu_cpu_stall_suppress, int, 0644); module_param(rcu_cpu_stall_timeout, int, 0644);