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 /* 24 * Simple, straightforward mutexes with strict semantics: 25 * 26 * - only one task can hold the mutex at a time 27 * - only the owner can unlock the mutex 28 * - multiple unlocks are not permitted 29 * - recursive locking is not permitted 30 * - a mutex object must be initialized via the API 31 * - a mutex object must not be initialized via memset or copying 32 * - task may not exit with mutex held 33 * - memory areas where held locks reside must not be freed 34 * - held mutexes must not be reinitialized 35 * - mutexes may not be used in hardware or software interrupt 36 * contexts such as tasklets and timers 37 * 38 * These semantics are fully enforced when DEBUG_MUTEXES is 39 * enabled. Furthermore, besides enforcing the above rules, the mutex 40 * debugging code also implements a number of additional features 41 * that make lock debugging easier and faster: 42 * 43 * - uses symbolic names of mutexes, whenever they are printed in debug output 44 * - point-of-acquire tracking, symbolic lookup of function names 45 * - list of all locks held in the system, printout of them 46 * - owner tracking 47 * - detects self-recursing locks and prints out all relevant info 48 * - detects multi-task circular deadlocks and prints out all affected 49 * locks and tasks (and only those tasks) 50 */ 51 struct mutex { 52 atomic_long_t owner; 53 raw_spinlock_t wait_lock; 54 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER 55 struct optimistic_spin_queue osq; /* Spinner MCS lock */ 56 #endif 57 struct list_head wait_list; 58 #ifdef CONFIG_DEBUG_MUTEXES 59 void *magic; 60 #endif 61 #ifdef CONFIG_DEBUG_LOCK_ALLOC 62 struct lockdep_map dep_map; 63 #endif 64 }; 65 66 #ifdef CONFIG_DEBUG_MUTEXES 67 68 #define __DEBUG_MUTEX_INITIALIZER(lockname) \ 69 , .magic = &lockname 70 71 extern void mutex_destroy(struct mutex *lock); 72 73 #else 74 75 # define __DEBUG_MUTEX_INITIALIZER(lockname) 76 77 static inline void mutex_destroy(struct mutex *lock) {} 78 79 #endif 80 81 /** 82 * mutex_init - initialize the mutex 83 * @mutex: the mutex to be initialized 84 * 85 * Initialize the mutex to unlocked state. 86 * 87 * It is not allowed to initialize an already locked mutex. 88 */ 89 #define mutex_init(mutex) \ 90 do { \ 91 static struct lock_class_key __key; \ 92 \ 93 __mutex_init((mutex), #mutex, &__key); \ 94 } while (0) 95 96 #ifdef CONFIG_DEBUG_LOCK_ALLOC 97 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ 98 , .dep_map = { \ 99 .name = #lockname, \ 100 .wait_type_inner = LD_WAIT_SLEEP, \ 101 } 102 #else 103 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) 104 #endif 105 106 #define __MUTEX_INITIALIZER(lockname) \ 107 { .owner = ATOMIC_LONG_INIT(0) \ 108 , .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(lockname.wait_lock) \ 109 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ 110 __DEBUG_MUTEX_INITIALIZER(lockname) \ 111 __DEP_MAP_MUTEX_INITIALIZER(lockname) } 112 113 #define DEFINE_MUTEX(mutexname) \ 114 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) 115 116 extern void __mutex_init(struct mutex *lock, const char *name, 117 struct lock_class_key *key); 118 119 /** 120 * mutex_is_locked - is the mutex locked 121 * @lock: the mutex to be queried 122 * 123 * Returns true if the mutex is locked, false if unlocked. 124 */ 125 extern bool mutex_is_locked(struct mutex *lock); 126 127 /* 128 * See kernel/locking/mutex.c for detailed documentation of these APIs. 129 * Also see Documentation/locking/mutex-design.rst. 130 */ 131 #ifdef CONFIG_DEBUG_LOCK_ALLOC 132 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 133 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); 134 135 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, 136 unsigned int subclass); 137 extern int __must_check mutex_lock_killable_nested(struct mutex *lock, 138 unsigned int subclass); 139 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass); 140 141 #define mutex_lock(lock) mutex_lock_nested(lock, 0) 142 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) 143 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) 144 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0) 145 146 #define mutex_lock_nest_lock(lock, nest_lock) \ 147 do { \ 148 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ 149 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \ 150 } while (0) 151 152 #else 153 extern void mutex_lock(struct mutex *lock); 154 extern int __must_check mutex_lock_interruptible(struct mutex *lock); 155 extern int __must_check mutex_lock_killable(struct mutex *lock); 156 extern void mutex_lock_io(struct mutex *lock); 157 158 # define mutex_lock_nested(lock, subclass) mutex_lock(lock) 159 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) 160 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) 161 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) 162 # define mutex_lock_io_nested(lock, subclass) mutex_lock_io(lock) 163 #endif 164 165 /* 166 * NOTE: mutex_trylock() follows the spin_trylock() convention, 167 * not the down_trylock() convention! 168 * 169 * Returns 1 if the mutex has been acquired successfully, and 0 on contention. 170 */ 171 extern int mutex_trylock(struct mutex *lock); 172 extern void mutex_unlock(struct mutex *lock); 173 174 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); 175 176 #endif /* __LINUX_MUTEX_H */ 177