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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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#ifndef __LINUX_RCUPDATE_H#define __LINUX_RCUPDATE_H
#include <linux/types.h>#include <linux/compiler.h>#include <linux/atomic.h>#include <linux/irqflags.h>#include <linux/sched.h>#include <linux/bottom_half.h>#include <linux/lockdep.h>#include <linux/cleanup.h>#include <asm/processor.h>#include <linux/context_tracking_irq.h>
token_context_lock(RCU, __reentrant_ctx_lock);token_context_lock_instance(RCU, RCU_SCHED);token_context_lock_instance(RCU, RCU_BH);
/* * A convenience macro that can be used for RCU-protected globals or struct * members; adds type qualifier __rcu, and also enforces __guarded_by(RCU). */#define __rcu_guarded __rcu __guarded_by(RCU)
#define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b))#define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b))
#define RCU_SEQ_CTR_SHIFT 2#define RCU_SEQ_STATE_MASK ((1 << RCU_SEQ_CTR_SHIFT) - 1)
/* Exported common interfaces */void call_rcu(struct rcu_head *head, rcu_callback_t func);void rcu_barrier_tasks(void);void synchronize_rcu(void);
struct rcu_gp_oldstate;unsigned long get_completed_synchronize_rcu(void);void get_completed_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
// Maximum number of unsigned long values corresponding to// not-yet-completed RCU grace periods.#define NUM_ACTIVE_RCU_POLL_OLDSTATE 2
/** * same_state_synchronize_rcu - Are two old-state values identical? * @oldstate1: First old-state value. * @oldstate2: Second old-state value. * * The two old-state values must have been obtained from either * get_state_synchronize_rcu(), start_poll_synchronize_rcu(), or * get_completed_synchronize_rcu(). Returns @true if the two values are * identical and @false otherwise. This allows structures whose lifetimes * are tracked by old-state values to push these values to a list header, * allowing those structures to be slightly smaller. */static inline bool same_state_synchronize_rcu(unsigned long oldstate1, unsigned long oldstate2){ return oldstate1 == oldstate2;}
#ifdef CONFIG_PREEMPT_RCU
void __rcu_read_lock(void);void __rcu_read_unlock(void);
/* * Defined as a macro as it is a very low level header included from * areas that don't even know about current. This gives the rcu_read_lock() * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. */#define rcu_preempt_depth() READ_ONCE(current->rcu_read_lock_nesting)
#else /* #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_TINY_RCU#define rcu_read_unlock_strict() do { } while (0)#elsevoid rcu_read_unlock_strict(void);#endif
static inline void __rcu_read_lock(void){ preempt_disable();}
static inline void __rcu_read_unlock(void){ if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) rcu_read_unlock_strict(); preempt_enable();}
static inline int rcu_preempt_depth(void){ return 0;}
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_RCU_LAZYvoid call_rcu_hurry(struct rcu_head *head, rcu_callback_t func);#elsestatic inline void call_rcu_hurry(struct rcu_head *head, rcu_callback_t func){ call_rcu(head, func);}#endif
/* Internal to kernel */void rcu_init(void);extern int rcu_scheduler_active;void rcu_sched_clock_irq(int user);
#ifdef CONFIG_RCU_STALL_COMMONvoid rcu_sysrq_start(void);void rcu_sysrq_end(void);#else /* #ifdef CONFIG_RCU_STALL_COMMON */static inline void rcu_sysrq_start(void) { }static inline void rcu_sysrq_end(void) { }#endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */
#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_VIRT_XFER_TO_GUEST_WORK))void rcu_irq_work_resched(void);#elsestatic __always_inline void rcu_irq_work_resched(void) { }#endif
#ifdef CONFIG_RCU_NOCB_CPUvoid rcu_init_nohz(void);int rcu_nocb_cpu_offload(int cpu);int rcu_nocb_cpu_deoffload(int cpu);void rcu_nocb_flush_deferred_wakeup(void);
#define RCU_NOCB_LOCKDEP_WARN(c, s) RCU_LOCKDEP_WARN(c, s)
#else /* #ifdef CONFIG_RCU_NOCB_CPU */
static inline void rcu_init_nohz(void) { }static inline int rcu_nocb_cpu_offload(int cpu) { return -EINVAL; }static inline int rcu_nocb_cpu_deoffload(int cpu) { return 0; }static inline void rcu_nocb_flush_deferred_wakeup(void) { }
#define RCU_NOCB_LOCKDEP_WARN(c, s)
#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
/* * Note a quasi-voluntary context switch for RCU-tasks's benefit. * This is a macro rather than an inline function to avoid #include hell. */#ifdef CONFIG_TASKS_RCU_GENERIC
# ifdef CONFIG_TASKS_RCU# define rcu_tasks_classic_qs(t, preempt) \ do { \ if (!(preempt) && READ_ONCE((t)->rcu_tasks_holdout)) \ WRITE_ONCE((t)->rcu_tasks_holdout, false); \ } while (0)void call_rcu_tasks(struct rcu_head *head, rcu_callback_t func);void synchronize_rcu_tasks(void);void rcu_tasks_torture_stats_print(char *tt, char *tf);# else# define rcu_tasks_classic_qs(t, preempt) do { } while (0)# define call_rcu_tasks call_rcu# define synchronize_rcu_tasks synchronize_rcu# endif
#define rcu_tasks_qs(t, preempt) rcu_tasks_classic_qs((t), (preempt))
# ifdef CONFIG_TASKS_RUDE_RCUvoid synchronize_rcu_tasks_rude(void);void rcu_tasks_rude_torture_stats_print(char *tt, char *tf);# endif
#define rcu_note_voluntary_context_switch(t) rcu_tasks_qs(t, false)void exit_tasks_rcu_start(void);void exit_tasks_rcu_finish(void);#else /* #ifdef CONFIG_TASKS_RCU_GENERIC */#define rcu_tasks_classic_qs(t, preempt) do { } while (0)#define rcu_tasks_qs(t, preempt) do { } while (0)#define rcu_note_voluntary_context_switch(t) do { } while (0)#define call_rcu_tasks call_rcu#define synchronize_rcu_tasks synchronize_rcustatic inline void exit_tasks_rcu_start(void) { }static inline void exit_tasks_rcu_finish(void) { }#endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */
/** * cond_resched_tasks_rcu_qs - Report potential quiescent states to RCU * * This macro resembles cond_resched(), except that it is defined to * report potential quiescent states to RCU-tasks even if the cond_resched() * machinery were to be shut off, as some advocate for PREEMPTION kernels. */#define cond_resched_tasks_rcu_qs() \do { \ rcu_tasks_qs(current, false); \ cond_resched(); \} while (0)
/** * rcu_softirq_qs_periodic - Report RCU and RCU-Tasks quiescent states * @old_ts: jiffies at start of processing. * * This helper is for long-running softirq handlers, such as NAPI threads in * networking. The caller should initialize the variable passed in as @old_ts * at the beginning of the softirq handler. When invoked frequently, this macro * will invoke rcu_softirq_qs() every 100 milliseconds thereafter, which will * provide both RCU and RCU-Tasks quiescent states. Note that this macro * modifies its old_ts argument. * * Because regions of code that have disabled softirq act as RCU read-side * critical sections, this macro should be invoked with softirq (and * preemption) enabled. * * The macro is not needed when CONFIG_PREEMPT_RT is defined. RT kernels would * have more chance to invoke schedule() calls and provide necessary quiescent * states. As a contrast, calling cond_resched() only won't achieve the same * effect because cond_resched() does not provide RCU-Tasks quiescent states. */#define rcu_softirq_qs_periodic(old_ts) \do { \ if (!IS_ENABLED(CONFIG_PREEMPT_RT) && \ time_after(jiffies, (old_ts) + HZ / 10)) { \ preempt_disable(); \ rcu_softirq_qs(); \ preempt_enable(); \ (old_ts) = jiffies; \ } \} while (0)
/* * Infrastructure to implement the synchronize_() primitives in * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. */
#if defined(CONFIG_TREE_RCU)#include <linux/rcutree.h>#elif defined(CONFIG_TINY_RCU)#include <linux/rcutiny.h>#else#error "Unknown RCU implementation specified to kernel configuration"#endif
/* * The init_rcu_head_on_stack() and destroy_rcu_head_on_stack() calls * are needed for dynamic initialization and destruction of rcu_head * on the stack, and init_rcu_head()/destroy_rcu_head() are needed for * dynamic initialization and destruction of statically allocated rcu_head * structures. However, rcu_head structures allocated dynamically in the * heap don't need any initialization. */#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEADvoid init_rcu_head(struct rcu_head *head);void destroy_rcu_head(struct rcu_head *head);void init_rcu_head_on_stack(struct rcu_head *head);void destroy_rcu_head_on_stack(struct rcu_head *head);#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */static inline void init_rcu_head(struct rcu_head *head) { }static inline void destroy_rcu_head(struct rcu_head *head) { }static inline void init_rcu_head_on_stack(struct rcu_head *head) { }static inline void destroy_rcu_head_on_stack(struct rcu_head *head) { }#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
#if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU)bool rcu_lockdep_current_cpu_online(void);#else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */static inline bool rcu_lockdep_current_cpu_online(void) { return true; }#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */
extern struct lockdep_map rcu_lock_map;extern struct lockdep_map rcu_bh_lock_map;extern struct lockdep_map rcu_sched_lock_map;extern struct lockdep_map rcu_callback_map;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static inline void rcu_lock_acquire(struct lockdep_map *map){ lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_);}
static inline void rcu_try_lock_acquire(struct lockdep_map *map){ lock_acquire(map, 0, 1, 2, 0, NULL, _THIS_IP_);}
static inline void rcu_lock_release(struct lockdep_map *map){ lock_release(map, _THIS_IP_);}
int debug_lockdep_rcu_enabled(void);int rcu_read_lock_held(void);int rcu_read_lock_bh_held(void);int rcu_read_lock_sched_held(void);int rcu_read_lock_any_held(void);
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
# define rcu_lock_acquire(a) do { } while (0)# define rcu_try_lock_acquire(a) do { } while (0)# define rcu_lock_release(a) do { } while (0)
static inline int rcu_read_lock_held(void){ return 1;}
static inline int rcu_read_lock_bh_held(void){ return 1;}
static inline int rcu_read_lock_sched_held(void){ return !preemptible();}
static inline int rcu_read_lock_any_held(void){ return !preemptible();}
static inline int debug_lockdep_rcu_enabled(void){ return 0;}
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
#ifdef CONFIG_PROVE_RCU
/** * RCU_LOCKDEP_WARN - emit lockdep splat if specified condition is met * @c: condition to check * @s: informative message * * This checks debug_lockdep_rcu_enabled() before checking (c) to * prevent early boot splats due to lockdep not yet being initialized, * and rechecks it after checking (c) to prevent false-positive splats * due to races with lockdep being disabled. See commit 3066820034b5dd * ("rcu: Reject RCU_LOCKDEP_WARN() false positives") for more detail. */#define RCU_LOCKDEP_WARN(c, s) \ do { \ static bool __section(".data..unlikely") __warned; \ if (debug_lockdep_rcu_enabled() && (c) && \ debug_lockdep_rcu_enabled() && !__warned) { \ __warned = true; \ lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ } \ } while (0)
#ifndef CONFIG_PREEMPT_RCUstatic inline void rcu_preempt_sleep_check(void){ RCU_LOCKDEP_WARN(lock_is_held(&rcu_lock_map), "Illegal context switch in RCU read-side critical section");}#else // #ifndef CONFIG_PREEMPT_RCUstatic inline void rcu_preempt_sleep_check(void) { }#endif // #else // #ifndef CONFIG_PREEMPT_RCU
#define rcu_sleep_check() \ do { \ rcu_preempt_sleep_check(); \ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) \ RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map), \ "Illegal context switch in RCU-bh read-side critical section"); \ RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map), \ "Illegal context switch in RCU-sched read-side critical section"); \ } while (0)
// See RCU_LOCKDEP_WARN() for an explanation of the double call to// debug_lockdep_rcu_enabled().static __always_inline bool lockdep_assert_rcu_helper(bool c, const struct __ctx_lock_RCU *ctx) __assumes_shared_ctx_lock(RCU) __assumes_shared_ctx_lock(ctx){ return debug_lockdep_rcu_enabled() && (c || !rcu_is_watching() || !rcu_lockdep_current_cpu_online()) && debug_lockdep_rcu_enabled();}
/** * lockdep_assert_in_rcu_read_lock - WARN if not protected by rcu_read_lock() * * Splats if lockdep is enabled and there is no rcu_read_lock() in effect. */#define lockdep_assert_in_rcu_read_lock() \ WARN_ON_ONCE(lockdep_assert_rcu_helper(!lock_is_held(&rcu_lock_map), RCU))
/** * lockdep_assert_in_rcu_read_lock_bh - WARN if not protected by rcu_read_lock_bh() * * Splats if lockdep is enabled and there is no rcu_read_lock_bh() in effect. * Note that local_bh_disable() and friends do not suffice here, instead an * actual rcu_read_lock_bh() is required. */#define lockdep_assert_in_rcu_read_lock_bh() \ WARN_ON_ONCE(lockdep_assert_rcu_helper(!lock_is_held(&rcu_bh_lock_map), RCU_BH))
/** * lockdep_assert_in_rcu_read_lock_sched - WARN if not protected by rcu_read_lock_sched() * * Splats if lockdep is enabled and there is no rcu_read_lock_sched() * in effect. Note that preempt_disable() and friends do not suffice here, * instead an actual rcu_read_lock_sched() is required. */#define lockdep_assert_in_rcu_read_lock_sched() \ WARN_ON_ONCE(lockdep_assert_rcu_helper(!lock_is_held(&rcu_sched_lock_map), RCU_SCHED))
/** * lockdep_assert_in_rcu_reader - WARN if not within some type of RCU reader * * Splats if lockdep is enabled and there is no RCU reader of any * type in effect. Note that regions of code protected by things like * preempt_disable, local_bh_disable(), and local_irq_disable() all qualify * as RCU readers. * * Note that this will never trigger in PREEMPT_NONE or PREEMPT_VOLUNTARY * kernels that are not also built with PREEMPT_COUNT. But if you have * lockdep enabled, you might as well also enable PREEMPT_COUNT. */#define lockdep_assert_in_rcu_reader() \ WARN_ON_ONCE(lockdep_assert_rcu_helper(!lock_is_held(&rcu_lock_map) && \ !lock_is_held(&rcu_bh_lock_map) && \ !lock_is_held(&rcu_sched_lock_map) && \ preemptible(), RCU))
#else /* #ifdef CONFIG_PROVE_RCU */
#define RCU_LOCKDEP_WARN(c, s) do { } while (0 && (c))#define rcu_sleep_check() do { } while (0)
#define lockdep_assert_in_rcu_read_lock() __assume_shared_ctx_lock(RCU)#define lockdep_assert_in_rcu_read_lock_bh() __assume_shared_ctx_lock(RCU_BH)#define lockdep_assert_in_rcu_read_lock_sched() __assume_shared_ctx_lock(RCU_SCHED)#define lockdep_assert_in_rcu_reader() __assume_shared_ctx_lock(RCU)
#endif /* #else #ifdef CONFIG_PROVE_RCU */
/* * Helper functions for rcu_dereference_check(), rcu_dereference_protected() * and rcu_assign_pointer(). Some of these could be folded into their * callers, but they are left separate in order to ease introduction of * multiple pointers markings to match different RCU implementations * (e.g., __srcu), should this make sense in the future. */
#ifdef __CHECKER__#define rcu_check_sparse(p, space) \ ((void)(((typeof(*p) space *)p) == p))#else /* #ifdef __CHECKER__ */#define rcu_check_sparse(p, space)#endif /* #else #ifdef __CHECKER__ */
#define __unrcu_pointer(p, local) \context_unsafe( \ typeof(*p) *local = (typeof(*p) *__force)(p); \ rcu_check_sparse(p, __rcu); \ ((typeof(*p) __force __kernel *)(local)) \)/** * unrcu_pointer - mark a pointer as not being RCU protected * @p: pointer needing to lose its __rcu property * * Converts @p from an __rcu pointer to a __kernel pointer. * This allows an __rcu pointer to be used with xchg() and friends. */#define unrcu_pointer(p) __unrcu_pointer(p, __UNIQUE_ID(rcu))
#define __rcu_access_pointer(p, local, space) \({ \ typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \ rcu_check_sparse(p, space); \ ((typeof(*p) __force __kernel *)(local)); \})#define __rcu_dereference_check(p, local, c, space) \({ \ /* Dependency order vs. p above. */ \ typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \ RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage"); \ rcu_check_sparse(p, space); \ ((typeof(*p) __force __kernel *)(local)); \})#define __rcu_dereference_protected(p, local, c, space) \({ \ RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \ rcu_check_sparse(p, space); \ ((typeof(*p) __force __kernel *)(p)); \})#define __rcu_dereference_raw(p, local) \({ \ /* Dependency order vs. p above. */ \ typeof(p) local = READ_ONCE(p); \ ((typeof(*p) __force __kernel *)(local)); \})#define rcu_dereference_raw(p) __rcu_dereference_raw(p, __UNIQUE_ID(rcu))
/** * RCU_INITIALIZER() - statically initialize an RCU-protected global variable * @v: The value to statically initialize with. */#define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v)
/** * rcu_assign_pointer() - assign to RCU-protected pointer * @p: pointer to assign to * @v: value to assign (publish) * * Assigns the specified value to the specified RCU-protected * pointer, ensuring that any concurrent RCU readers will see * any prior initialization. * * Inserts memory barriers on architectures that require them * (which is most of them), and also prevents the compiler from * reordering the code that initializes the structure after the pointer * assignment. More importantly, this call documents which pointers * will be dereferenced by RCU read-side code. * * In some special cases, you may use RCU_INIT_POINTER() instead * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due * to the fact that it does not constrain either the CPU or the compiler. * That said, using RCU_INIT_POINTER() when you should have used * rcu_assign_pointer() is a very bad thing that results in * impossible-to-diagnose memory corruption. So please be careful. * See the RCU_INIT_POINTER() comment header for details. * * Note that rcu_assign_pointer() evaluates each of its arguments only * once, appearances notwithstanding. One of the "extra" evaluations * is in typeof() and the other visible only to sparse (__CHECKER__), * neither of which actually execute the argument. As with most cpp * macros, this execute-arguments-only-once property is important, so * please be careful when making changes to rcu_assign_pointer() and the * other macros that it invokes. */#define rcu_assign_pointer(p, v) \context_unsafe( \ uintptr_t _r_a_p__v = (uintptr_t)(v); \ rcu_check_sparse(p, __rcu); \ \ if (__builtin_constant_p(v) && (_r_a_p__v) == (uintptr_t)NULL) \ WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \ else \ smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \)
/** * rcu_replace_pointer() - replace an RCU pointer, returning its old value * @rcu_ptr: RCU pointer, whose old value is returned * @ptr: regular pointer * @c: the lockdep conditions under which the dereference will take place * * Perform a replacement, where @rcu_ptr is an RCU-annotated * pointer and @c is the lockdep argument that is passed to the * rcu_dereference_protected() call used to read that pointer. The old * value of @rcu_ptr is returned, and @rcu_ptr is set to @ptr. */#define rcu_replace_pointer(rcu_ptr, ptr, c) \({ \ typeof(ptr) __tmp = rcu_dereference_protected((rcu_ptr), (c)); \ rcu_assign_pointer((rcu_ptr), (ptr)); \ __tmp; \})
/** * rcu_access_pointer() - fetch RCU pointer with no dereferencing * @p: The pointer to read * * Return the value of the specified RCU-protected pointer, but omit the * lockdep checks for being in an RCU read-side critical section. This is * useful when the value of this pointer is accessed, but the pointer is * not dereferenced, for example, when testing an RCU-protected pointer * against NULL. Within an RCU read-side critical section, there is little * reason to use rcu_access_pointer(). Although rcu_access_pointer() may * also be used in cases where update-side locks prevent the value of the * pointer from changing, you should instead use rcu_dereference_protected() * for this use case. It is also permissible to use rcu_access_pointer() * within lockless updaters to obtain the old value for an atomic operation, * for example, for cmpxchg(). * * It is usually best to test the rcu_access_pointer() return value * directly in order to avoid accidental dereferences being introduced * by later inattentive changes. In other words, assigning the * rcu_access_pointer() return value to a local variable results in an * accident waiting to happen. * * It is also permissible to use rcu_access_pointer() when read-side * access to the pointer was removed at least one grace period ago, as is * the case in the context of the RCU callback that is freeing up the data, * or after a synchronize_rcu() returns. This can be useful when tearing * down multi-linked structures after a grace period has elapsed. However, * rcu_dereference_protected() is normally preferred for this use case. */#define rcu_access_pointer(p) __rcu_access_pointer((p), __UNIQUE_ID(rcu), __rcu)
/** * rcu_dereference_check() - rcu_dereference with debug checking * @p: The pointer to read, prior to dereferencing * @c: The conditions under which the dereference will take place * * Do an rcu_dereference(), but check that the conditions under which the * dereference will take place are correct. Typically the conditions * indicate the various locking conditions that should be held at that * point. The check should return true if the conditions are satisfied. * An implicit check for being in an RCU read-side critical section * (rcu_read_lock()) is included. * * For example: * * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); * * could be used to indicate to lockdep that foo->bar may only be dereferenced * if either rcu_read_lock() is held, or that the lock required to replace * the bar struct at foo->bar is held. * * Note that the list of conditions may also include indications of when a lock * need not be held, for example during initialisation or destruction of the * target struct: * * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || * atomic_read(&foo->usage) == 0); * * Inserts memory barriers on architectures that require them * (currently only the Alpha), prevents the compiler from refetching * (and from merging fetches), and, more importantly, documents exactly * which pointers are protected by RCU and checks that the pointer is * annotated as __rcu. */#define rcu_dereference_check(p, c) \ __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ (c) || rcu_read_lock_held(), __rcu)
/** * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking * @p: The pointer to read, prior to dereferencing * @c: The conditions under which the dereference will take place * * This is the RCU-bh counterpart to rcu_dereference_check(). However, * please note that starting in v5.0 kernels, vanilla RCU grace periods * wait for local_bh_disable() regions of code in addition to regions of * code demarked by rcu_read_lock() and rcu_read_unlock(). This means * that synchronize_rcu(), call_rcu, and friends all take not only * rcu_read_lock() but also rcu_read_lock_bh() into account. */#define rcu_dereference_bh_check(p, c) \ __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ (c) || rcu_read_lock_bh_held(), __rcu)
/** * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking * @p: The pointer to read, prior to dereferencing * @c: The conditions under which the dereference will take place * * This is the RCU-sched counterpart to rcu_dereference_check(). * However, please note that starting in v5.0 kernels, vanilla RCU grace * periods wait for preempt_disable() regions of code in addition to * regions of code demarked by rcu_read_lock() and rcu_read_unlock(). * This means that synchronize_rcu(), call_rcu, and friends all take not * only rcu_read_lock() but also rcu_read_lock_sched() into account. */#define rcu_dereference_sched_check(p, c) \ __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ (c) || rcu_read_lock_sched_held(), \ __rcu)
/** * rcu_dereference_all_check() - rcu_dereference_all with debug checking * @p: The pointer to read, prior to dereferencing * @c: The conditions under which the dereference will take place * * This is similar to rcu_dereference_check(), but allows protection * by all forms of vanilla RCU readers, including preemption disabled, * bh-disabled, and interrupt-disabled regions of code. Note that "vanilla * RCU" excludes SRCU and the various Tasks RCU flavors. Please note * that this macro should not be backported to any Linux-kernel version * preceding v5.0 due to changes in synchronize_rcu() semantics prior * to that version. */#define rcu_dereference_all_check(p, c) \ __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ (c) || rcu_read_lock_any_held(), \ __rcu)
/* * The tracing infrastructure traces RCU (we want that), but unfortunately * some of the RCU checks causes tracing to lock up the system. * * The no-tracing version of rcu_dereference_raw() must not call * rcu_read_lock_held(). */#define rcu_dereference_raw_check(p) \ __rcu_dereference_check((p), __UNIQUE_ID(rcu), 1, __rcu)
/** * rcu_dereference_protected() - fetch RCU pointer when updates prevented * @p: The pointer to read, prior to dereferencing * @c: The conditions under which the dereference will take place * * Return the value of the specified RCU-protected pointer, but omit * the READ_ONCE(). This is useful in cases where update-side locks * prevent the value of the pointer from changing. Please note that this * primitive does *not* prevent the compiler from repeating this reference * or combining it with other references, so it should not be used without * protection of appropriate locks. * * This function is only for update-side use. Using this function * when protected only by rcu_read_lock() will result in infrequent * but very ugly failures. */#define rcu_dereference_protected(p, c) \ __rcu_dereference_protected((p), __UNIQUE_ID(rcu), (c), __rcu)
/** * rcu_dereference() - fetch RCU-protected pointer for dereferencing * @p: The pointer to read, prior to dereferencing * * This is a simple wrapper around rcu_dereference_check(). */#define rcu_dereference(p) rcu_dereference_check(p, 0)
/** * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing * @p: The pointer to read, prior to dereferencing * * Makes rcu_dereference_check() do the dirty work. */#define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0)
/** * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing * @p: The pointer to read, prior to dereferencing * * Makes rcu_dereference_check() do the dirty work. */#define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0)
/** * rcu_dereference_all() - fetch RCU-all-protected pointer for dereferencing * @p: The pointer to read, prior to dereferencing * * Makes rcu_dereference_check() do the dirty work. */#define rcu_dereference_all(p) rcu_dereference_all_check(p, 0)
/** * rcu_pointer_handoff() - Hand off a pointer from RCU to other mechanism * @p: The pointer to hand off * * This is simply an identity function, but it documents where a pointer * is handed off from RCU to some other synchronization mechanism, for * example, reference counting or locking. In C11, it would map to * kill_dependency(). It could be used as follows:: * * rcu_read_lock(); * p = rcu_dereference(gp); * long_lived = is_long_lived(p); * if (long_lived) { * if (!atomic_inc_not_zero(p->refcnt)) * long_lived = false; * else * p = rcu_pointer_handoff(p); * } * rcu_read_unlock(); */#define rcu_pointer_handoff(p) (p)
/** * rcu_read_lock() - mark the beginning of an RCU read-side critical section * * When synchronize_rcu() is invoked on one CPU while other CPUs * are within RCU read-side critical sections, then the * synchronize_rcu() is guaranteed to block until after all the other * CPUs exit their critical sections. Similarly, if call_rcu() is invoked * on one CPU while other CPUs are within RCU read-side critical * sections, invocation of the corresponding RCU callback is deferred * until after the all the other CPUs exit their critical sections. * * Both synchronize_rcu() and call_rcu() also wait for regions of code * with preemption disabled, including regions of code with interrupts or * softirqs disabled. * * Note, however, that RCU callbacks are permitted to run concurrently * with new RCU read-side critical sections. One way that this can happen * is via the following sequence of events: (1) CPU 0 enters an RCU * read-side critical section, (2) CPU 1 invokes call_rcu() to register * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU * callback is invoked. This is legal, because the RCU read-side critical * section that was running concurrently with the call_rcu() (and which * therefore might be referencing something that the corresponding RCU * callback would free up) has completed before the corresponding * RCU callback is invoked. * * RCU read-side critical sections may be nested. Any deferred actions * will be deferred until the outermost RCU read-side critical section * completes. * * You can avoid reading and understanding the next paragraph by * following this rule: don't put anything in an rcu_read_lock() RCU * read-side critical section that would block in a !PREEMPTION kernel. * But if you want the full story, read on! * * In non-preemptible RCU implementations (pure TREE_RCU and TINY_RCU), * it is illegal to block while in an RCU read-side critical section. * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPTION * kernel builds, RCU read-side critical sections may be preempted, * but explicit blocking is illegal. Finally, in preemptible RCU * implementations in real-time (with -rt patchset) kernel builds, RCU * read-side critical sections may be preempted and they may also block, but * only when acquiring spinlocks that are subject to priority inheritance. */static __always_inline void rcu_read_lock(void) __acquires_shared(RCU){ __rcu_read_lock(); __acquire_shared(RCU); rcu_lock_acquire(&rcu_lock_map); RCU_LOCKDEP_WARN(!rcu_is_watching(), "rcu_read_lock() used illegally while idle");}
/* * So where is rcu_write_lock()? It does not exist, as there is no * way for writers to lock out RCU readers. This is a feature, not * a bug -- this property is what provides RCU's performance benefits. * Of course, writers must coordinate with each other. The normal * spinlock primitives work well for this, but any other technique may be * used as well. RCU does not care how the writers keep out of each * others' way, as long as they do so. */
/** * rcu_read_unlock() - marks the end of an RCU read-side critical section. * * In almost all situations, rcu_read_unlock() is immune from deadlock. * This deadlock immunity also extends to the scheduler's runqueue * and priority-inheritance spinlocks, courtesy of the quiescent-state * deferral that is carried out when rcu_read_unlock() is invoked with * interrupts disabled. * * See rcu_read_lock() for more information. */static inline void rcu_read_unlock(void) __releases_shared(RCU){ RCU_LOCKDEP_WARN(!rcu_is_watching(), "rcu_read_unlock() used illegally while idle"); rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */ __release_shared(RCU); __rcu_read_unlock();}
/** * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section * * This is equivalent to rcu_read_lock(), but also disables softirqs. * Note that anything else that disables softirqs can also serve as an RCU * read-side critical section. However, please note that this equivalence * applies only to v5.0 and later. Before v5.0, rcu_read_lock() and * rcu_read_lock_bh() were unrelated. * * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() * must occur in the same context, for example, it is illegal to invoke * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() * was invoked from some other task. */static inline void rcu_read_lock_bh(void) __acquires_shared(RCU) __acquires_shared(RCU_BH){ local_bh_disable(); __acquire_shared(RCU); __acquire_shared(RCU_BH); rcu_lock_acquire(&rcu_bh_lock_map); RCU_LOCKDEP_WARN(!rcu_is_watching(), "rcu_read_lock_bh() used illegally while idle");}
/** * rcu_read_unlock_bh() - marks the end of a softirq-only RCU critical section * * See rcu_read_lock_bh() for more information. */static inline void rcu_read_unlock_bh(void) __releases_shared(RCU) __releases_shared(RCU_BH){ RCU_LOCKDEP_WARN(!rcu_is_watching(), "rcu_read_unlock_bh() used illegally while idle"); rcu_lock_release(&rcu_bh_lock_map); __release_shared(RCU_BH); __release_shared(RCU); local_bh_enable();}
/** * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section * * This is equivalent to rcu_read_lock(), but also disables preemption. * Read-side critical sections can also be introduced by anything else that * disables preemption, including local_irq_disable() and friends. However, * please note that the equivalence to rcu_read_lock() applies only to * v5.0 and later. Before v5.0, rcu_read_lock() and rcu_read_lock_sched() * were unrelated. * * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() * must occur in the same context, for example, it is illegal to invoke * rcu_read_unlock_sched() from process context if the matching * rcu_read_lock_sched() was invoked from an NMI handler. */static inline void rcu_read_lock_sched(void) __acquires_shared(RCU) __acquires_shared(RCU_SCHED){ preempt_disable(); __acquire_shared(RCU); __acquire_shared(RCU_SCHED); rcu_lock_acquire(&rcu_sched_lock_map); RCU_LOCKDEP_WARN(!rcu_is_watching(), "rcu_read_lock_sched() used illegally while idle");}
/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */static inline notrace void rcu_read_lock_sched_notrace(void) __acquires_shared(RCU) __acquires_shared(RCU_SCHED){ preempt_disable_notrace(); __acquire_shared(RCU); __acquire_shared(RCU_SCHED);}
/** * rcu_read_unlock_sched() - marks the end of a RCU-classic critical section * * See rcu_read_lock_sched() for more information. */static inline void rcu_read_unlock_sched(void) __releases_shared(RCU) __releases_shared(RCU_SCHED){ RCU_LOCKDEP_WARN(!rcu_is_watching(), "rcu_read_unlock_sched() used illegally while idle"); rcu_lock_release(&rcu_sched_lock_map); __release_shared(RCU_SCHED); __release_shared(RCU); preempt_enable();}
/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */static inline notrace void rcu_read_unlock_sched_notrace(void) __releases_shared(RCU) __releases_shared(RCU_SCHED){ __release_shared(RCU_SCHED); __release_shared(RCU); preempt_enable_notrace();}
static __always_inline void rcu_read_lock_dont_migrate(void) __acquires_shared(RCU){ if (IS_ENABLED(CONFIG_PREEMPT_RCU)) migrate_disable(); rcu_read_lock();}
static inline void rcu_read_unlock_migrate(void) __releases_shared(RCU){ rcu_read_unlock(); if (IS_ENABLED(CONFIG_PREEMPT_RCU)) migrate_enable();}
/** * RCU_INIT_POINTER() - initialize an RCU protected pointer * @p: The pointer to be initialized. * @v: The value to initialized the pointer to. * * Initialize an RCU-protected pointer in special cases where readers * do not need ordering constraints on the CPU or the compiler. These * special cases are: * * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer *or* * 2. The caller has taken whatever steps are required to prevent * RCU readers from concurrently accessing this pointer *or* * 3. The referenced data structure has already been exposed to * readers either at compile time or via rcu_assign_pointer() *and* * * a. You have not made *any* reader-visible changes to * this structure since then *or* * b. It is OK for readers accessing this structure from its * new location to see the old state of the structure. (For * example, the changes were to statistical counters or to * other state where exact synchronization is not required.) * * Failure to follow these rules governing use of RCU_INIT_POINTER() will * result in impossible-to-diagnose memory corruption. As in the structures * will look OK in crash dumps, but any concurrent RCU readers might * see pre-initialized values of the referenced data structure. So * please be very careful how you use RCU_INIT_POINTER()!!! * * If you are creating an RCU-protected linked structure that is accessed * by a single external-to-structure RCU-protected pointer, then you may * use RCU_INIT_POINTER() to initialize the internal RCU-protected * pointers, but you must use rcu_assign_pointer() to initialize the * external-to-structure pointer *after* you have completely initialized * the reader-accessible portions of the linked structure. * * Note that unlike rcu_assign_pointer(), RCU_INIT_POINTER() provides no * ordering guarantees for either the CPU or the compiler. */#define RCU_INIT_POINTER(p, v) \ context_unsafe( \ rcu_check_sparse(p, __rcu); \ WRITE_ONCE(p, RCU_INITIALIZER(v)); \ )
/** * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer * @p: The pointer to be initialized. * @v: The value to initialized the pointer to. * * GCC-style initialization for an RCU-protected pointer in a structure field. */#define RCU_POINTER_INITIALIZER(p, v) \ .p = RCU_INITIALIZER(v)
/** * kfree_rcu() - kfree an object after a grace period. * @ptr: pointer to kfree for double-argument invocations. * @rhf: the name of the struct rcu_head within the type of @ptr. * * Many rcu callbacks functions just call kfree() on the base structure. * These functions are trivial, but their size adds up, and furthermore * when they are used in a kernel module, that module must invoke the * high-latency rcu_barrier() function at module-unload time. * * The kfree_rcu() function handles this issue. In order to have a universal * callback function handling different offsets of rcu_head, the callback needs * to determine the starting address of the freed object, which can be a large * kmalloc or vmalloc allocation. To allow simply aligning the pointer down to * page boundary for those, only offsets up to 4095 bytes can be accommodated. * If the offset is larger than 4095 bytes, a compile-time error will * be generated in kvfree_rcu_arg_2(). If this error is triggered, you can * either fall back to use of call_rcu() or rearrange the structure to * position the rcu_head structure into the first 4096 bytes. * * The object to be freed can be allocated either by kmalloc(), * kmalloc_nolock(), or kmem_cache_alloc(). * * Note that the allowable offset might decrease in the future. * * The BUILD_BUG_ON check must not involve any function calls, hence the * checks are done in macros here. */#define kfree_rcu(ptr, rhf) kvfree_rcu_arg_2(ptr, rhf)#define kvfree_rcu(ptr, rhf) kvfree_rcu_arg_2(ptr, rhf)
/** * kfree_rcu_mightsleep() - kfree an object after a grace period. * @ptr: pointer to kfree for single-argument invocations. * * When it comes to head-less variant, only one argument * is passed and that is just a pointer which has to be * freed after a grace period. Therefore the semantic is * * kfree_rcu_mightsleep(ptr); * * where @ptr is the pointer to be freed by kvfree(). * * Please note, head-less way of freeing is permitted to * use from a context that has to follow might_sleep() * annotation. Otherwise, please switch and embed the * rcu_head structure within the type of @ptr. */#define kfree_rcu_mightsleep(ptr) kvfree_rcu_arg_1(ptr)#define kvfree_rcu_mightsleep(ptr) kvfree_rcu_arg_1(ptr)
/* * In mm/slab_common.c, no suitable header to include here. */void kvfree_call_rcu(struct rcu_head *head, void *ptr);
/* * The BUILD_BUG_ON() makes sure the rcu_head offset can be handled. See the * comment of kfree_rcu() for details. */#define kvfree_rcu_arg_2(ptr, rhf) \do { \ typeof (ptr) ___p = (ptr); \ \ if (___p) { \ BUILD_BUG_ON(offsetof(typeof(*(ptr)), rhf) >= 4096); \ kvfree_call_rcu(&((___p)->rhf), (void *) (___p)); \ } \} while (0)
#define kvfree_rcu_arg_1(ptr) \do { \ typeof(ptr) ___p = (ptr); \ \ if (___p) \ kvfree_call_rcu(NULL, (void *) (___p)); \} while (0)
/* * Place this after a lock-acquisition primitive to guarantee that * an UNLOCK+LOCK pair acts as a full barrier. This guarantee applies * if the UNLOCK and LOCK are executed by the same CPU or if the * UNLOCK and LOCK operate on the same lock variable. */#ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE#define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */#else /* #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */#define smp_mb__after_unlock_lock() do { } while (0)#endif /* #else #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */
/* Has the specified rcu_head structure been handed to call_rcu()? */
/** * rcu_head_init - Initialize rcu_head for rcu_head_after_call_rcu() * @rhp: The rcu_head structure to initialize. * * If you intend to invoke rcu_head_after_call_rcu() to test whether a * given rcu_head structure has already been passed to call_rcu(), then * you must also invoke this rcu_head_init() function on it just after * allocating that structure. Calls to this function must not race with * calls to call_rcu(), rcu_head_after_call_rcu(), or callback invocation. */static inline void rcu_head_init(struct rcu_head *rhp){ rhp->func = (rcu_callback_t)~0L;}
/** * rcu_head_after_call_rcu() - Has this rcu_head been passed to call_rcu()? * @rhp: The rcu_head structure to test. * @f: The function passed to call_rcu() along with @rhp. * * Returns @true if the @rhp has been passed to call_rcu() with @func, * and @false otherwise. Emits a warning in any other case, including * the case where @rhp has already been invoked after a grace period. * Calls to this function must not race with callback invocation. One way * to avoid such races is to enclose the call to rcu_head_after_call_rcu() * in an RCU read-side critical section that includes a read-side fetch * of the pointer to the structure containing @rhp. */static inline boolrcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f){ rcu_callback_t func = READ_ONCE(rhp->func);
if (func == f) return true; WARN_ON_ONCE(func != (rcu_callback_t)~0L); return false;}
/* kernel/ksysfs.c definitions */extern int rcu_expedited;extern int rcu_normal;
DEFINE_LOCK_GUARD_0(rcu, rcu_read_lock(), rcu_read_unlock())DECLARE_LOCK_GUARD_0_ATTRS(rcu, __acquires_shared(RCU), __releases_shared(RCU))
#endif /* __LINUX_RCUPDATE_H */