1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Mutexes: blocking mutual exclusion locks 4 * 5 * started by Ingo Molnar: 6 * 7 * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <[email protected]> 8 * 9 * This file contains the main data structure and API definitions. 10 */ 11 #ifndef __LINUX_MUTEX_H 12 #define __LINUX_MUTEX_H 13 14 #include <asm/current.h> 15 #include <linux/list.h> 16 #include <linux/spinlock_types.h> 17 #include <linux/lockdep.h> 18 #include <linux/atomic.h> 19 #include <asm/processor.h> 20 #include <linux/osq_lock.h> 21 #include <linux/debug_locks.h> 22 23 struct ww_acquire_ctx; 24 25 /* 26 * Simple, straightforward mutexes with strict semantics: 27 * 28 * - only one task can hold the mutex at a time 29 * - only the owner can unlock the mutex 30 * - multiple unlocks are not permitted 31 * - recursive locking is not permitted 32 * - a mutex object must be initialized via the API 33 * - a mutex object must not be initialized via memset or copying 34 * - task may not exit with mutex held 35 * - memory areas where held locks reside must not be freed 36 * - held mutexes must not be reinitialized 37 * - mutexes may not be used in hardware or software interrupt 38 * contexts such as tasklets and timers 39 * 40 * These semantics are fully enforced when DEBUG_MUTEXES is 41 * enabled. Furthermore, besides enforcing the above rules, the mutex 42 * debugging code also implements a number of additional features 43 * that make lock debugging easier and faster: 44 * 45 * - uses symbolic names of mutexes, whenever they are printed in debug output 46 * - point-of-acquire tracking, symbolic lookup of function names 47 * - list of all locks held in the system, printout of them 48 * - owner tracking 49 * - detects self-recursing locks and prints out all relevant info 50 * - detects multi-task circular deadlocks and prints out all affected 51 * locks and tasks (and only those tasks) 52 */ 53 struct mutex { 54 atomic_long_t owner; 55 spinlock_t wait_lock; 56 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER 57 struct optimistic_spin_queue osq; /* Spinner MCS lock */ 58 #endif 59 struct list_head wait_list; 60 #ifdef CONFIG_DEBUG_MUTEXES 61 void *magic; 62 #endif 63 #ifdef CONFIG_DEBUG_LOCK_ALLOC 64 struct lockdep_map dep_map; 65 #endif 66 }; 67 68 #ifdef CONFIG_DEBUG_MUTEXES 69 70 #define __DEBUG_MUTEX_INITIALIZER(lockname) \ 71 , .magic = &lockname 72 73 extern void mutex_destroy(struct mutex *lock); 74 75 #else 76 77 # define __DEBUG_MUTEX_INITIALIZER(lockname) 78 79 static inline void mutex_destroy(struct mutex *lock) {} 80 81 #endif 82 83 /** 84 * mutex_init - initialize the mutex 85 * @mutex: the mutex to be initialized 86 * 87 * Initialize the mutex to unlocked state. 88 * 89 * It is not allowed to initialize an already locked mutex. 90 */ 91 #define mutex_init(mutex) \ 92 do { \ 93 static struct lock_class_key __key; \ 94 \ 95 __mutex_init((mutex), #mutex, &__key); \ 96 } while (0) 97 98 #ifdef CONFIG_DEBUG_LOCK_ALLOC 99 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ 100 , .dep_map = { .name = #lockname } 101 #else 102 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) 103 #endif 104 105 #define __MUTEX_INITIALIZER(lockname) \ 106 { .owner = ATOMIC_LONG_INIT(0) \ 107 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \ 108 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ 109 __DEBUG_MUTEX_INITIALIZER(lockname) \ 110 __DEP_MAP_MUTEX_INITIALIZER(lockname) } 111 112 #define DEFINE_MUTEX(mutexname) \ 113 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) 114 115 extern void __mutex_init(struct mutex *lock, const char *name, 116 struct lock_class_key *key); 117 118 /** 119 * mutex_is_locked - is the mutex locked 120 * @lock: the mutex to be queried 121 * 122 * Returns true if the mutex is locked, false if unlocked. 123 */ 124 extern bool mutex_is_locked(struct mutex *lock); 125 126 /* 127 * See kernel/locking/mutex.c for detailed documentation of these APIs. 128 * Also see Documentation/locking/mutex-design.rst. 129 */ 130 #ifdef CONFIG_DEBUG_LOCK_ALLOC 131 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 132 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); 133 134 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, 135 unsigned int subclass); 136 extern int __must_check mutex_lock_killable_nested(struct mutex *lock, 137 unsigned int subclass); 138 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass); 139 140 #define mutex_lock(lock) mutex_lock_nested(lock, 0) 141 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) 142 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) 143 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0) 144 145 #define mutex_lock_nest_lock(lock, nest_lock) \ 146 do { \ 147 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ 148 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \ 149 } while (0) 150 151 #else 152 extern void mutex_lock(struct mutex *lock); 153 extern int __must_check mutex_lock_interruptible(struct mutex *lock); 154 extern int __must_check mutex_lock_killable(struct mutex *lock); 155 extern void mutex_lock_io(struct mutex *lock); 156 157 # define mutex_lock_nested(lock, subclass) mutex_lock(lock) 158 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) 159 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) 160 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) 161 # define mutex_lock_io_nested(lock, subclass) mutex_lock(lock) 162 #endif 163 164 /* 165 * NOTE: mutex_trylock() follows the spin_trylock() convention, 166 * not the down_trylock() convention! 167 * 168 * Returns 1 if the mutex has been acquired successfully, and 0 on contention. 169 */ 170 extern int mutex_trylock(struct mutex *lock); 171 extern void mutex_unlock(struct mutex *lock); 172 173 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); 174 175 /* 176 * These values are chosen such that FAIL and SUCCESS match the 177 * values of the regular mutex_trylock(). 178 */ 179 enum mutex_trylock_recursive_enum { 180 MUTEX_TRYLOCK_FAILED = 0, 181 MUTEX_TRYLOCK_SUCCESS = 1, 182 MUTEX_TRYLOCK_RECURSIVE, 183 }; 184 185 /** 186 * mutex_trylock_recursive - trylock variant that allows recursive locking 187 * @lock: mutex to be locked 188 * 189 * This function should not be used, _ever_. It is purely for hysterical GEM 190 * raisins, and once those are gone this will be removed. 191 * 192 * Returns: 193 * - MUTEX_TRYLOCK_FAILED - trylock failed, 194 * - MUTEX_TRYLOCK_SUCCESS - lock acquired, 195 * - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock. 196 */ 197 extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum 198 mutex_trylock_recursive(struct mutex *lock); 199 200 #endif /* __LINUX_MUTEX_H */ 201