mutex.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef __PERF_MUTEX_H
  3#define __PERF_MUTEX_H
  4
  5#include <pthread.h>
  6#include <stdbool.h>
  7
  8/*
  9 * A function-like feature checking macro that is a wrapper around
 10 * `__has_attribute`, which is defined by GCC 5+ and Clang and evaluates to a
 11 * nonzero constant integer if the attribute is supported or 0 if not.
 12 */
 13#ifdef __has_attribute
 14#define HAVE_ATTRIBUTE(x) __has_attribute(x)
 15#else
 16#define HAVE_ATTRIBUTE(x) 0
 17#endif
 18
 19#if HAVE_ATTRIBUTE(guarded_by) && HAVE_ATTRIBUTE(pt_guarded_by) && \
 20	HAVE_ATTRIBUTE(lockable) && HAVE_ATTRIBUTE(exclusive_lock_function) && \
 21	HAVE_ATTRIBUTE(exclusive_trylock_function) && HAVE_ATTRIBUTE(exclusive_locks_required) && \
 22	HAVE_ATTRIBUTE(no_thread_safety_analysis)
 23
 24/* Documents if a shared field or global variable needs to be protected by a mutex. */
 25#define GUARDED_BY(x) __attribute__((guarded_by(x)))
 26
 27/*
 28 * Documents if the memory location pointed to by a pointer should be guarded by
 29 * a mutex when dereferencing the pointer.
 30 */
 31#define PT_GUARDED_BY(x) __attribute__((pt_guarded_by(x)))
 32
 33/* Documents if a type is a lockable type. */
 34#define LOCKABLE __attribute__((lockable))
 35
 36/* Documents a function that expects a lock not to be held prior to entry. */
 37#define LOCKS_EXCLUDED(...) __attribute__((locks_excluded(__VA_ARGS__)))
 38
 39/* Documents a function that returns a lock. */
 40#define LOCK_RETURNED(x) __attribute__((lock_returned(x)))
 41
 42/* Documents functions that acquire a lock in the body of a function, and do not release it. */
 43#define EXCLUSIVE_LOCK_FUNCTION(...)  __attribute__((exclusive_lock_function(__VA_ARGS__)))
 44
 45/*
 46 * Documents functions that acquire a shared (reader) lock in the body of a
 47 * function, and do not release it.
 48 */
 49#define SHARED_LOCK_FUNCTION(...)  __attribute__((shared_lock_function(__VA_ARGS__)))
 50
 51/*
 52 * Documents functions that expect a lock to be held on entry to the function,
 53 * and release it in the body of the function.
 54 */
 55#define UNLOCK_FUNCTION(...) __attribute__((unlock_function(__VA_ARGS__)))
 56
 57/* Documents functions that try to acquire a lock, and return success or failure. */
 58#define EXCLUSIVE_TRYLOCK_FUNCTION(...) \
 59	__attribute__((exclusive_trylock_function(__VA_ARGS__)))
 60
 61/* Documents a function that expects a mutex to be held prior to entry. */
 62#define EXCLUSIVE_LOCKS_REQUIRED(...) __attribute__((exclusive_locks_required(__VA_ARGS__)))
 63
 64/* Documents a function that expects a shared (reader) lock to be held prior to entry. */
 65#define SHARED_LOCKS_REQUIRED(...) __attribute__((shared_locks_required(__VA_ARGS__)))
 66
 67/* Turns off thread safety checking within the body of a particular function. */
 68#define NO_THREAD_SAFETY_ANALYSIS __attribute__((no_thread_safety_analysis))
 69
 70#else
 71
 72#define GUARDED_BY(x)
 73#define PT_GUARDED_BY(x)
 74#define LOCKABLE
 75#define LOCKS_EXCLUDED(...)
 76#define LOCK_RETURNED(x)
 77#define EXCLUSIVE_LOCK_FUNCTION(...)
 78#define SHARED_LOCK_FUNCTION(...)
 79#define UNLOCK_FUNCTION(...)
 80#define EXCLUSIVE_TRYLOCK_FUNCTION(...)
 81#define EXCLUSIVE_LOCKS_REQUIRED(...)
 82#define SHARED_LOCKS_REQUIRED(...)
 83#define NO_THREAD_SAFETY_ANALYSIS
 84
 85#endif
 86
 87/*
 88 * A wrapper around the mutex implementation that allows perf to error check
 89 * usage, etc.
 90 */
 91struct LOCKABLE mutex {
 92	pthread_mutex_t lock;
 93};
 94
 95/* A wrapper around the condition variable implementation. */
 96struct cond {
 97	pthread_cond_t cond;
 98};
 99
100/* Default initialize the mtx struct. */
101void mutex_init(struct mutex *mtx);
102/*
103 * Initialize the mtx struct and set the process-shared rather than default
104 * process-private attribute.
105 */
106void mutex_init_pshared(struct mutex *mtx);
107/* Initializes a mutex that may be recursively held on the same thread. */
108void mutex_init_recursive(struct mutex *mtx);
109void mutex_destroy(struct mutex *mtx);
110
111void mutex_lock(struct mutex *mtx) EXCLUSIVE_LOCK_FUNCTION(*mtx);
112void mutex_unlock(struct mutex *mtx) UNLOCK_FUNCTION(*mtx);
113/* Tries to acquire the lock and returns true on success. */
114bool mutex_trylock(struct mutex *mtx) EXCLUSIVE_TRYLOCK_FUNCTION(true, *mtx);
115
116/* Default initialize the cond struct. */
117void cond_init(struct cond *cnd);
118/*
119 * Initialize the cond struct and specify the process-shared rather than default
120 * process-private attribute.
121 */
122void cond_init_pshared(struct cond *cnd);
123void cond_destroy(struct cond *cnd);
124
125void cond_wait(struct cond *cnd, struct mutex *mtx) EXCLUSIVE_LOCKS_REQUIRED(mtx);
126void cond_signal(struct cond *cnd);
127void cond_broadcast(struct cond *cnd);
128
129#endif /* __PERF_MUTEX_H */