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 static inline struct task_struct *__mutex_owner(struct mutex *lock) 70 { 71 return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07); 72 } 73 74 /* 75 * This is the control structure for tasks blocked on mutex, 76 * which resides on the blocked task's kernel stack: 77 */ 78 struct mutex_waiter { 79 struct list_head list; 80 struct task_struct *task; 81 struct ww_acquire_ctx *ww_ctx; 82 #ifdef CONFIG_DEBUG_MUTEXES 83 void *magic; 84 #endif 85 }; 86 87 #ifdef CONFIG_DEBUG_MUTEXES 88 89 #define __DEBUG_MUTEX_INITIALIZER(lockname) \ 90 , .magic = &lockname 91 92 extern void mutex_destroy(struct mutex *lock); 93 94 #else 95 96 # define __DEBUG_MUTEX_INITIALIZER(lockname) 97 98 static inline void mutex_destroy(struct mutex *lock) {} 99 100 #endif 101 102 /** 103 * mutex_init - initialize the mutex 104 * @mutex: the mutex to be initialized 105 * 106 * Initialize the mutex to unlocked state. 107 * 108 * It is not allowed to initialize an already locked mutex. 109 */ 110 #define mutex_init(mutex) \ 111 do { \ 112 static struct lock_class_key __key; \ 113 \ 114 __mutex_init((mutex), #mutex, &__key); \ 115 } while (0) 116 117 #ifdef CONFIG_DEBUG_LOCK_ALLOC 118 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ 119 , .dep_map = { .name = #lockname } 120 #else 121 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) 122 #endif 123 124 #define __MUTEX_INITIALIZER(lockname) \ 125 { .owner = ATOMIC_LONG_INIT(0) \ 126 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \ 127 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ 128 __DEBUG_MUTEX_INITIALIZER(lockname) \ 129 __DEP_MAP_MUTEX_INITIALIZER(lockname) } 130 131 #define DEFINE_MUTEX(mutexname) \ 132 struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) 133 134 extern void __mutex_init(struct mutex *lock, const char *name, 135 struct lock_class_key *key); 136 137 /** 138 * mutex_is_locked - is the mutex locked 139 * @lock: the mutex to be queried 140 * 141 * Returns 1 if the mutex is locked, 0 if unlocked. 142 */ 143 static inline int mutex_is_locked(struct mutex *lock) 144 { 145 /* 146 * XXX think about spin_is_locked 147 */ 148 return __mutex_owner(lock) != NULL; 149 } 150 151 /* 152 * See kernel/locking/mutex.c for detailed documentation of these APIs. 153 * Also see Documentation/locking/mutex-design.txt. 154 */ 155 #ifdef CONFIG_DEBUG_LOCK_ALLOC 156 extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); 157 extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); 158 159 extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, 160 unsigned int subclass); 161 extern int __must_check mutex_lock_killable_nested(struct mutex *lock, 162 unsigned int subclass); 163 extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass); 164 165 #define mutex_lock(lock) mutex_lock_nested(lock, 0) 166 #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) 167 #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) 168 #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0) 169 170 #define mutex_lock_nest_lock(lock, nest_lock) \ 171 do { \ 172 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ 173 _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \ 174 } while (0) 175 176 #else 177 extern void mutex_lock(struct mutex *lock); 178 extern int __must_check mutex_lock_interruptible(struct mutex *lock); 179 extern int __must_check mutex_lock_killable(struct mutex *lock); 180 extern void mutex_lock_io(struct mutex *lock); 181 182 # define mutex_lock_nested(lock, subclass) mutex_lock(lock) 183 # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) 184 # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) 185 # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) 186 # define mutex_lock_io_nested(lock, subclass) mutex_lock(lock) 187 #endif 188 189 /* 190 * NOTE: mutex_trylock() follows the spin_trylock() convention, 191 * not the down_trylock() convention! 192 * 193 * Returns 1 if the mutex has been acquired successfully, and 0 on contention. 194 */ 195 extern int mutex_trylock(struct mutex *lock); 196 extern void mutex_unlock(struct mutex *lock); 197 198 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); 199 200 /* 201 * These values are chosen such that FAIL and SUCCESS match the 202 * values of the regular mutex_trylock(). 203 */ 204 enum mutex_trylock_recursive_enum { 205 MUTEX_TRYLOCK_FAILED = 0, 206 MUTEX_TRYLOCK_SUCCESS = 1, 207 MUTEX_TRYLOCK_RECURSIVE, 208 }; 209 210 /** 211 * mutex_trylock_recursive - trylock variant that allows recursive locking 212 * @lock: mutex to be locked 213 * 214 * This function should not be used, _ever_. It is purely for hysterical GEM 215 * raisins, and once those are gone this will be removed. 216 * 217 * Returns: 218 * - MUTEX_TRYLOCK_FAILED - trylock failed, 219 * - MUTEX_TRYLOCK_SUCCESS - lock acquired, 220 * - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock. 221 */ 222 static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum 223 mutex_trylock_recursive(struct mutex *lock) 224 { 225 if (unlikely(__mutex_owner(lock) == current)) 226 return MUTEX_TRYLOCK_RECURSIVE; 227 228 return mutex_trylock(lock); 229 } 230 231 #endif /* __LINUX_MUTEX_H */ 232