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 #ifdef CONFIG_DEBUG_LOCK_ALLOC 24 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ 25 , .dep_map = { \ 26 .name = #lockname, \ 27 .wait_type_inner = LD_WAIT_SLEEP, \ 28 } 29 #else 30 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) 31 #endif 32 33 #ifndef CONFIG_PREEMPT_RT 34 35 /* 36 * Simple, straightforward mutexes with strict semantics: 37 * 38 * - only one task can hold the mutex at a time 39 * - only the owner can unlock the mutex 40 * - multiple unlocks are not permitted 41 * - recursive locking is not permitted 42 * - a mutex object must be initialized via the API 43 * - a mutex object must not be initialized via memset or copying 44 * - task may not exit with mutex held 45 * - memory areas where held locks reside must not be freed 46 * - held mutexes must not be reinitialized 47 * - mutexes may not be used in hardware or software interrupt 48 * contexts such as tasklets and timers 49 * 50 * These semantics are fully enforced when DEBUG_MUTEXES is 51 * enabled. Furthermore, besides enforcing the above rules, the mutex 52 * debugging code also implements a number of additional features 53 * that make lock debugging easier and faster: 54 * 55 * - uses symbolic names of mutexes, whenever they are printed in debug output 56 * - point-of-acquire tracking, symbolic lookup of function names 57 * - list of all locks held in the system, printout of them 58 * - owner tracking 59 * - detects self-recursing locks and prints out all relevant info 60 * - detects multi-task circular deadlocks and prints out all affected 61 * locks and tasks (and only those tasks) 62 */ 63 struct mutex { 64 atomic_long_t owner; 65 raw_spinlock_t wait_lock; 66 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER 67 struct optimistic_spin_queue osq; /* Spinner MCS lock */ 68 #endif 69 struct list_head wait_list; 70 #ifdef CONFIG_DEBUG_MUTEXES 71 void *magic; 72 #endif 73 #ifdef CONFIG_DEBUG_LOCK_ALLOC 74 struct lockdep_map dep_map; 75 #endif 76 }; 77 78 #ifdef CONFIG_DEBUG_MUTEXES 79 80 #define __DEBUG_MUTEX_INITIALIZER(lockname) \ 81 , .magic = &lockname 82 83 extern void mutex_destroy(struct mutex *lock); 84 85 #else 86 87 # define __DEBUG_MUTEX_INITIALIZER(lockname) 88 89 static inline void mutex_destroy(struct mutex *lock) {} 90 91 #endif 92 93 /** 94 * mutex_init - initialize the mutex 95 * @mutex: the mutex to be initialized 96 * 97 * Initialize the mutex to unlocked state. 98 * 99 * It is not allowed to initialize an already locked mutex. 100 */ 101 #define mutex_init(mutex) \ 102 do { \ 103 static struct lock_class_key __key; \ 104 \ 105 __mutex_init((mutex), #mutex, &__key); \ 106 } while (0) 107 108 #define __MUTEX_INITIALIZER(lockname) \ 109 { .owner = ATOMIC_LONG_INIT(0) \ 110 , .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(lockname.wait_lock) \ 111 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ 112 __DEBUG_MUTEX_INITIALIZER(lockname) \ 113 __DEP_MAP_MUTEX_INITIALIZER(lockname) } 114 115 #define DEFINE_MUTEX(mutexname) \ 116 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) 117 118 extern void __mutex_init(struct mutex *lock, const char *name, 119 struct lock_class_key *key); 120 121 /** 122 * mutex_is_locked - is the mutex locked 123 * @lock: the mutex to be queried 124 * 125 * Returns true if the mutex is locked, false if unlocked. 126 */ 127 extern bool mutex_is_locked(struct mutex *lock); 128 129 #else /* !CONFIG_PREEMPT_RT */ 130 /* 131 * Preempt-RT variant based on rtmutexes. 132 */ 133 #include <linux/rtmutex.h> 134 135 struct mutex { 136 struct rt_mutex_base rtmutex; 137 #ifdef CONFIG_DEBUG_LOCK_ALLOC 138 struct lockdep_map dep_map; 139 #endif 140 }; 141 142 #define __MUTEX_INITIALIZER(mutexname) \ 143 { \ 144 .rtmutex = __RT_MUTEX_BASE_INITIALIZER(mutexname.rtmutex) \ 145 __DEP_MAP_MUTEX_INITIALIZER(mutexname) \ 146 } 147 148 #define DEFINE_MUTEX(mutexname) \ 149 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) 150 151 extern void __mutex_rt_init(struct mutex *lock, const char *name, 152 struct lock_class_key *key); 153 extern int mutex_trylock(struct mutex *lock); 154 155 static inline void mutex_destroy(struct mutex *lock) { } 156 157 #define mutex_is_locked(l) rt_mutex_base_is_locked(&(l)->rtmutex) 158 159 #define __mutex_init(mutex, name, key) \ 160 do { \ 161 rt_mutex_base_init(&(mutex)->rtmutex); \ 162 __mutex_rt_init((mutex), name, key); \ 163 } while (0) 164 165 #define mutex_init(mutex) \ 166 do { \ 167 static struct lock_class_key __key; \ 168 \ 169 __mutex_init((mutex), #mutex, &__key); \ 170 } while (0) 171 #endif /* CONFIG_PREEMPT_RT */ 172 173 /* 174 * See kernel/locking/mutex.c for detailed documentation of these APIs. 175 * Also see Documentation/locking/mutex-design.rst. 176 */ 177 #ifdef CONFIG_DEBUG_LOCK_ALLOC 178 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 179 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); 180 181 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, 182 unsigned int subclass); 183 extern int __must_check mutex_lock_killable_nested(struct mutex *lock, 184 unsigned int subclass); 185 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass); 186 187 #define mutex_lock(lock) mutex_lock_nested(lock, 0) 188 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) 189 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) 190 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0) 191 192 #define mutex_lock_nest_lock(lock, nest_lock) \ 193 do { \ 194 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ 195 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \ 196 } while (0) 197 198 #else 199 extern void mutex_lock(struct mutex *lock); 200 extern int __must_check mutex_lock_interruptible(struct mutex *lock); 201 extern int __must_check mutex_lock_killable(struct mutex *lock); 202 extern void mutex_lock_io(struct mutex *lock); 203 204 # define mutex_lock_nested(lock, subclass) mutex_lock(lock) 205 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) 206 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) 207 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) 208 # define mutex_lock_io_nested(lock, subclass) mutex_lock_io(lock) 209 #endif 210 211 /* 212 * NOTE: mutex_trylock() follows the spin_trylock() convention, 213 * not the down_trylock() convention! 214 * 215 * Returns 1 if the mutex has been acquired successfully, and 0 on contention. 216 */ 217 extern int mutex_trylock(struct mutex *lock); 218 extern void mutex_unlock(struct mutex *lock); 219 220 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); 221 222 #endif /* __LINUX_MUTEX_H */ 223