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/linkage.h> 18 #include <linux/lockdep.h> 19 #include <linux/atomic.h> 20 #include <asm/processor.h> 21 #include <linux/osq_lock.h> 22 #include <linux/debug_locks.h> 23 24 struct ww_acquire_ctx; 25 26 /* 27 * Simple, straightforward mutexes with strict semantics: 28 * 29 * - only one task can hold the mutex at a time 30 * - only the owner can unlock the mutex 31 * - multiple unlocks are not permitted 32 * - recursive locking is not permitted 33 * - a mutex object must be initialized via the API 34 * - a mutex object must not be initialized via memset or copying 35 * - task may not exit with mutex held 36 * - memory areas where held locks reside must not be freed 37 * - held mutexes must not be reinitialized 38 * - mutexes may not be used in hardware or software interrupt 39 * contexts such as tasklets and timers 40 * 41 * These semantics are fully enforced when DEBUG_MUTEXES is 42 * enabled. Furthermore, besides enforcing the above rules, the mutex 43 * debugging code also implements a number of additional features 44 * that make lock debugging easier and faster: 45 * 46 * - uses symbolic names of mutexes, whenever they are printed in debug output 47 * - point-of-acquire tracking, symbolic lookup of function names 48 * - list of all locks held in the system, printout of them 49 * - owner tracking 50 * - detects self-recursing locks and prints out all relevant info 51 * - detects multi-task circular deadlocks and prints out all affected 52 * locks and tasks (and only those tasks) 53 */ 54 struct mutex { 55 atomic_long_t owner; 56 spinlock_t wait_lock; 57 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER 58 struct optimistic_spin_queue osq; /* Spinner MCS lock */ 59 #endif 60 struct list_head wait_list; 61 #ifdef CONFIG_DEBUG_MUTEXES 62 void *magic; 63 #endif 64 #ifdef CONFIG_DEBUG_LOCK_ALLOC 65 struct lockdep_map dep_map; 66 #endif 67 }; 68 69 /* 70 * Internal helper function; C doesn't allow us to hide it :/ 71 * 72 * DO NOT USE (outside of mutex code). 73 */ 74 static inline struct task_struct *__mutex_owner(struct mutex *lock) 75 { 76 return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07); 77 } 78 79 /* 80 * This is the control structure for tasks blocked on mutex, 81 * which resides on the blocked task's kernel stack: 82 */ 83 struct mutex_waiter { 84 struct list_head list; 85 struct task_struct *task; 86 struct ww_acquire_ctx *ww_ctx; 87 #ifdef CONFIG_DEBUG_MUTEXES 88 void *magic; 89 #endif 90 }; 91 92 #ifdef CONFIG_DEBUG_MUTEXES 93 94 #define __DEBUG_MUTEX_INITIALIZER(lockname) \ 95 , .magic = &lockname 96 97 extern void mutex_destroy(struct mutex *lock); 98 99 #else 100 101 # define __DEBUG_MUTEX_INITIALIZER(lockname) 102 103 static inline void mutex_destroy(struct mutex *lock) {} 104 105 #endif 106 107 /** 108 * mutex_init - initialize the mutex 109 * @mutex: the mutex to be initialized 110 * 111 * Initialize the mutex to unlocked state. 112 * 113 * It is not allowed to initialize an already locked mutex. 114 */ 115 #define mutex_init(mutex) \ 116 do { \ 117 static struct lock_class_key __key; \ 118 \ 119 __mutex_init((mutex), #mutex, &__key); \ 120 } while (0) 121 122 #ifdef CONFIG_DEBUG_LOCK_ALLOC 123 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ 124 , .dep_map = { .name = #lockname } 125 #else 126 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) 127 #endif 128 129 #define __MUTEX_INITIALIZER(lockname) \ 130 { .owner = ATOMIC_LONG_INIT(0) \ 131 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \ 132 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ 133 __DEBUG_MUTEX_INITIALIZER(lockname) \ 134 __DEP_MAP_MUTEX_INITIALIZER(lockname) } 135 136 #define DEFINE_MUTEX(mutexname) \ 137 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) 138 139 extern void __mutex_init(struct mutex *lock, const char *name, 140 struct lock_class_key *key); 141 142 /** 143 * mutex_is_locked - is the mutex locked 144 * @lock: the mutex to be queried 145 * 146 * Returns true if the mutex is locked, false if unlocked. 147 */ 148 static inline bool mutex_is_locked(struct mutex *lock) 149 { 150 /* 151 * XXX think about spin_is_locked 152 */ 153 return __mutex_owner(lock) != NULL; 154 } 155 156 /* 157 * See kernel/locking/mutex.c for detailed documentation of these APIs. 158 * Also see Documentation/locking/mutex-design.txt. 159 */ 160 #ifdef CONFIG_DEBUG_LOCK_ALLOC 161 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 162 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); 163 164 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, 165 unsigned int subclass); 166 extern int __must_check mutex_lock_killable_nested(struct mutex *lock, 167 unsigned int subclass); 168 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass); 169 170 #define mutex_lock(lock) mutex_lock_nested(lock, 0) 171 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) 172 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) 173 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0) 174 175 #define mutex_lock_nest_lock(lock, nest_lock) \ 176 do { \ 177 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ 178 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \ 179 } while (0) 180 181 #else 182 extern void mutex_lock(struct mutex *lock); 183 extern int __must_check mutex_lock_interruptible(struct mutex *lock); 184 extern int __must_check mutex_lock_killable(struct mutex *lock); 185 extern void mutex_lock_io(struct mutex *lock); 186 187 # define mutex_lock_nested(lock, subclass) mutex_lock(lock) 188 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) 189 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) 190 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) 191 # define mutex_lock_io_nested(lock, subclass) mutex_lock(lock) 192 #endif 193 194 /* 195 * NOTE: mutex_trylock() follows the spin_trylock() convention, 196 * not the down_trylock() convention! 197 * 198 * Returns 1 if the mutex has been acquired successfully, and 0 on contention. 199 */ 200 extern int mutex_trylock(struct mutex *lock); 201 extern void mutex_unlock(struct mutex *lock); 202 203 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); 204 205 /* 206 * These values are chosen such that FAIL and SUCCESS match the 207 * values of the regular mutex_trylock(). 208 */ 209 enum mutex_trylock_recursive_enum { 210 MUTEX_TRYLOCK_FAILED = 0, 211 MUTEX_TRYLOCK_SUCCESS = 1, 212 MUTEX_TRYLOCK_RECURSIVE, 213 }; 214 215 /** 216 * mutex_trylock_recursive - trylock variant that allows recursive locking 217 * @lock: mutex to be locked 218 * 219 * This function should not be used, _ever_. It is purely for hysterical GEM 220 * raisins, and once those are gone this will be removed. 221 * 222 * Returns: 223 * - MUTEX_TRYLOCK_FAILED - trylock failed, 224 * - MUTEX_TRYLOCK_SUCCESS - lock acquired, 225 * - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock. 226 */ 227 static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum 228 mutex_trylock_recursive(struct mutex *lock) 229 { 230 if (unlikely(__mutex_owner(lock) == current)) 231 return MUTEX_TRYLOCK_RECURSIVE; 232 233 return mutex_trylock(lock); 234 } 235 236 #endif /* __LINUX_MUTEX_H */ 237