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Diffstat (limited to 'include/linux/srcu.h')
| -rw-r--r-- | include/linux/srcu.h | 351 |
1 files changed, 351 insertions, 0 deletions
diff --git a/include/linux/srcu.h b/include/linux/srcu.h new file mode 100644 index 000000000..236610e4a --- /dev/null +++ b/include/linux/srcu.h @@ -0,0 +1,351 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Sleepable Read-Copy Update mechanism for mutual exclusion + * + * Copyright (C) IBM Corporation, 2006 + * Copyright (C) Fujitsu, 2012 + * + * Author: Paul McKenney <paulmck@linux.ibm.com> + * Lai Jiangshan <laijs@cn.fujitsu.com> + * + * For detailed explanation of Read-Copy Update mechanism see - + * Documentation/RCU/ *.txt + * + */ + +#ifndef _LINUX_SRCU_H +#define _LINUX_SRCU_H + +#include <linux/mutex.h> +#include <linux/rcupdate.h> +#include <linux/workqueue.h> +#include <linux/rcu_segcblist.h> + +struct srcu_struct; + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +int __init_srcu_struct(struct srcu_struct *ssp, const char *name, + struct lock_class_key *key); + +#define init_srcu_struct(ssp) \ +({ \ + static struct lock_class_key __srcu_key; \ + \ + __init_srcu_struct((ssp), #ssp, &__srcu_key); \ +}) + +#define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name }, +#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +int init_srcu_struct(struct srcu_struct *ssp); + +#define __SRCU_DEP_MAP_INIT(srcu_name) +#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +#ifdef CONFIG_TINY_SRCU +#include <linux/srcutiny.h> +#elif defined(CONFIG_TREE_SRCU) +#include <linux/srcutree.h> +#else +#error "Unknown SRCU implementation specified to kernel configuration" +#endif + +void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, + void (*func)(struct rcu_head *head)); +void cleanup_srcu_struct(struct srcu_struct *ssp); +int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); +void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); +void synchronize_srcu(struct srcu_struct *ssp); +unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp); +unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp); +bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); + +#ifdef CONFIG_NEED_SRCU_NMI_SAFE +int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp); +void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp); +#else +static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) +{ + return __srcu_read_lock(ssp); +} +static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) +{ + __srcu_read_unlock(ssp, idx); +} +#endif /* CONFIG_NEED_SRCU_NMI_SAFE */ + +void srcu_init(void); + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +/** + * srcu_read_lock_held - might we be in SRCU read-side critical section? + * @ssp: The srcu_struct structure to check + * + * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU + * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, + * this assumes we are in an SRCU read-side critical section unless it can + * prove otherwise. + * + * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot + * and while lockdep is disabled. + * + * Note that SRCU is based on its own statemachine and it doesn't + * relies on normal RCU, it can be called from the CPU which + * is in the idle loop from an RCU point of view or offline. + */ +static inline int srcu_read_lock_held(const struct srcu_struct *ssp) +{ + if (!debug_lockdep_rcu_enabled()) + return 1; + return lock_is_held(&ssp->dep_map); +} + +/* + * Annotations provide deadlock detection for SRCU. + * + * Similar to other lockdep annotations, except there is an additional + * srcu_lock_sync(), which is basically an empty *write*-side critical section, + * see lock_sync() for more information. + */ + +/* Annotates a srcu_read_lock() */ +static inline void srcu_lock_acquire(struct lockdep_map *map) +{ + lock_map_acquire_read(map); +} + +/* Annotates a srcu_read_lock() */ +static inline void srcu_lock_release(struct lockdep_map *map) +{ + lock_map_release(map); +} + +/* Annotates a synchronize_srcu() */ +static inline void srcu_lock_sync(struct lockdep_map *map) +{ + lock_map_sync(map); +} + +#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +static inline int srcu_read_lock_held(const struct srcu_struct *ssp) +{ + return 1; +} + +#define srcu_lock_acquire(m) do { } while (0) +#define srcu_lock_release(m) do { } while (0) +#define srcu_lock_sync(m) do { } while (0) + +#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +#define SRCU_NMI_UNKNOWN 0x0 +#define SRCU_NMI_UNSAFE 0x1 +#define SRCU_NMI_SAFE 0x2 + +#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) +void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe); +#else +static inline void srcu_check_nmi_safety(struct srcu_struct *ssp, + bool nmi_safe) { } +#endif + + +/** + * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing + * @p: the pointer to fetch and protect for later dereferencing + * @ssp: pointer to the srcu_struct, which is used to check that we + * really are in an SRCU read-side critical section. + * @c: condition to check for update-side use + * + * If PROVE_RCU is enabled, invoking this outside of an RCU read-side + * critical section will result in an RCU-lockdep splat, unless @c evaluates + * to 1. The @c argument will normally be a logical expression containing + * lockdep_is_held() calls. + */ +#define srcu_dereference_check(p, ssp, c) \ + __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ + (c) || srcu_read_lock_held(ssp), __rcu) + +/** + * srcu_dereference - fetch SRCU-protected pointer for later dereferencing + * @p: the pointer to fetch and protect for later dereferencing + * @ssp: pointer to the srcu_struct, which is used to check that we + * really are in an SRCU read-side critical section. + * + * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU + * is enabled, invoking this outside of an RCU read-side critical + * section will result in an RCU-lockdep splat. + */ +#define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0) + +/** + * srcu_dereference_notrace - no tracing and no lockdep calls from here + * @p: the pointer to fetch and protect for later dereferencing + * @ssp: pointer to the srcu_struct, which is used to check that we + * really are in an SRCU read-side critical section. + */ +#define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1) + +/** + * srcu_read_lock - register a new reader for an SRCU-protected structure. + * @ssp: srcu_struct in which to register the new reader. + * + * Enter an SRCU read-side critical section. Note that SRCU read-side + * critical sections may be nested. However, it is illegal to + * call anything that waits on an SRCU grace period for the same + * srcu_struct, whether directly or indirectly. Please note that + * one way to indirectly wait on an SRCU grace period is to acquire + * a mutex that is held elsewhere while calling synchronize_srcu() or + * synchronize_srcu_expedited(). + * + * Note that srcu_read_lock() and the matching srcu_read_unlock() must + * occur in the same context, for example, it is illegal to invoke + * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() + * was invoked in process context. + */ +static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) +{ + int retval; + + srcu_check_nmi_safety(ssp, false); + retval = __srcu_read_lock(ssp); + srcu_lock_acquire(&ssp->dep_map); + return retval; +} + +/** + * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure. + * @ssp: srcu_struct in which to register the new reader. + * + * Enter an SRCU read-side critical section, but in an NMI-safe manner. + * See srcu_read_lock() for more information. + */ +static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp) +{ + int retval; + + srcu_check_nmi_safety(ssp, true); + retval = __srcu_read_lock_nmisafe(ssp); + rcu_try_lock_acquire(&ssp->dep_map); + return retval; +} + +/* Used by tracing, cannot be traced and cannot invoke lockdep. */ +static inline notrace int +srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) +{ + int retval; + + srcu_check_nmi_safety(ssp, false); + retval = __srcu_read_lock(ssp); + return retval; +} + +/** + * srcu_down_read - register a new reader for an SRCU-protected structure. + * @ssp: srcu_struct in which to register the new reader. + * + * Enter a semaphore-like SRCU read-side critical section. Note that + * SRCU read-side critical sections may be nested. However, it is + * illegal to call anything that waits on an SRCU grace period for the + * same srcu_struct, whether directly or indirectly. Please note that + * one way to indirectly wait on an SRCU grace period is to acquire + * a mutex that is held elsewhere while calling synchronize_srcu() or + * synchronize_srcu_expedited(). But if you want lockdep to help you + * keep this stuff straight, you should instead use srcu_read_lock(). + * + * The semaphore-like nature of srcu_down_read() means that the matching + * srcu_up_read() can be invoked from some other context, for example, + * from some other task or from an irq handler. However, neither + * srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler. + * + * Calls to srcu_down_read() may be nested, similar to the manner in + * which calls to down_read() may be nested. + */ +static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) +{ + WARN_ON_ONCE(in_nmi()); + srcu_check_nmi_safety(ssp, false); + return __srcu_read_lock(ssp); +} + +/** + * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. + * @ssp: srcu_struct in which to unregister the old reader. + * @idx: return value from corresponding srcu_read_lock(). + * + * Exit an SRCU read-side critical section. + */ +static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) + __releases(ssp) +{ + WARN_ON_ONCE(idx & ~0x1); + srcu_check_nmi_safety(ssp, false); + srcu_lock_release(&ssp->dep_map); + __srcu_read_unlock(ssp, idx); +} + +/** + * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure. + * @ssp: srcu_struct in which to unregister the old reader. + * @idx: return value from corresponding srcu_read_lock(). + * + * Exit an SRCU read-side critical section, but in an NMI-safe manner. + */ +static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) + __releases(ssp) +{ + WARN_ON_ONCE(idx & ~0x1); + srcu_check_nmi_safety(ssp, true); + rcu_lock_release(&ssp->dep_map); + __srcu_read_unlock_nmisafe(ssp, idx); +} + +/* Used by tracing, cannot be traced and cannot call lockdep. */ +static inline notrace void +srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) +{ + srcu_check_nmi_safety(ssp, false); + __srcu_read_unlock(ssp, idx); +} + +/** + * srcu_up_read - unregister a old reader from an SRCU-protected structure. + * @ssp: srcu_struct in which to unregister the old reader. + * @idx: return value from corresponding srcu_read_lock(). + * + * Exit an SRCU read-side critical section, but not necessarily from + * the same context as the maching srcu_down_read(). + */ +static inline void srcu_up_read(struct srcu_struct *ssp, int idx) + __releases(ssp) +{ + WARN_ON_ONCE(idx & ~0x1); + WARN_ON_ONCE(in_nmi()); + srcu_check_nmi_safety(ssp, false); + __srcu_read_unlock(ssp, idx); +} + +/** + * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock + * + * Converts the preceding srcu_read_unlock into a two-way memory barrier. + * + * Call this after srcu_read_unlock, to guarantee that all memory operations + * that occur after smp_mb__after_srcu_read_unlock will appear to happen after + * the preceding srcu_read_unlock. + */ +static inline void smp_mb__after_srcu_read_unlock(void) +{ + /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ +} + +DEFINE_LOCK_GUARD_1(srcu, struct srcu_struct, + _T->idx = srcu_read_lock(_T->lock), + srcu_read_unlock(_T->lock, _T->idx), + int idx) + +#endif |