| 1 | /* |
| 2 | * Mutexes: blocking mutual exclusion locks |
| 3 | * |
| 4 | * started by Ingo Molnar: |
| 5 | * |
| 6 | * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> |
| 7 | * |
| 8 | * This file contains the main data structure and API definitions. |
| 9 | */ |
| 10 | #ifndef __LINUX_MUTEX_H |
| 11 | #define __LINUX_MUTEX_H |
| 12 | |
| 13 | #include <asm/current.h> |
| 14 | #include <linux/list.h> |
| 15 | #include <linux/spinlock_types.h> |
| 16 | #include <linux/linkage.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 | static inline struct task_struct *__mutex_owner(struct mutex *lock) |
| 69 | { |
| 70 | return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07); |
| 71 | } |
| 72 | |
| 73 | /* |
| 74 | * This is the control structure for tasks blocked on mutex, |
| 75 | * which resides on the blocked task's kernel stack: |
| 76 | */ |
| 77 | struct mutex_waiter { |
| 78 | struct list_head list; |
| 79 | struct task_struct *task; |
| 80 | struct ww_acquire_ctx *ww_ctx; |
| 81 | #ifdef CONFIG_DEBUG_MUTEXES |
| 82 | void *magic; |
| 83 | #endif |
| 84 | }; |
| 85 | |
| 86 | #ifdef CONFIG_DEBUG_MUTEXES |
| 87 | |
| 88 | #define __DEBUG_MUTEX_INITIALIZER(lockname) \ |
| 89 | , .magic = &lockname |
| 90 | |
| 91 | extern void mutex_destroy(struct mutex *lock); |
| 92 | |
| 93 | #else |
| 94 | |
| 95 | # define __DEBUG_MUTEX_INITIALIZER(lockname) |
| 96 | |
| 97 | static inline void mutex_destroy(struct mutex *lock) {} |
| 98 | |
| 99 | #endif |
| 100 | |
| 101 | /** |
| 102 | * mutex_init - initialize the mutex |
| 103 | * @mutex: the mutex to be initialized |
| 104 | * |
| 105 | * Initialize the mutex to unlocked state. |
| 106 | * |
| 107 | * It is not allowed to initialize an already locked mutex. |
| 108 | */ |
| 109 | #define mutex_init(mutex) \ |
| 110 | do { \ |
| 111 | static struct lock_class_key __key; \ |
| 112 | \ |
| 113 | __mutex_init((mutex), #mutex, &__key); \ |
| 114 | } while (0) |
| 115 | |
| 116 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 117 | # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ |
| 118 | , .dep_map = { .name = #lockname } |
| 119 | #else |
| 120 | # define __DEP_MAP_MUTEX_INITIALIZER(lockname) |
| 121 | #endif |
| 122 | |
| 123 | #define __MUTEX_INITIALIZER(lockname) \ |
| 124 | { .owner = ATOMIC_LONG_INIT(0) \ |
| 125 | , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \ |
| 126 | , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ |
| 127 | __DEBUG_MUTEX_INITIALIZER(lockname) \ |
| 128 | __DEP_MAP_MUTEX_INITIALIZER(lockname) } |
| 129 | |
| 130 | #define DEFINE_MUTEX(mutexname) \ |
| 131 | struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) |
| 132 | |
| 133 | extern void __mutex_init(struct mutex *lock, const char *name, |
| 134 | struct lock_class_key *key); |
| 135 | |
| 136 | /** |
| 137 | * mutex_is_locked - is the mutex locked |
| 138 | * @lock: the mutex to be queried |
| 139 | * |
| 140 | * Returns 1 if the mutex is locked, 0 if unlocked. |
| 141 | */ |
| 142 | static inline int mutex_is_locked(struct mutex *lock) |
| 143 | { |
| 144 | /* |
| 145 | * XXX think about spin_is_locked |
| 146 | */ |
| 147 | return __mutex_owner(lock) != NULL; |
| 148 | } |
| 149 | |
| 150 | /* |
| 151 | * See kernel/locking/mutex.c for detailed documentation of these APIs. |
| 152 | * Also see Documentation/locking/mutex-design.txt. |
| 153 | */ |
| 154 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 155 | extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); |
| 156 | extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); |
| 157 | |
| 158 | extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, |
| 159 | unsigned int subclass); |
| 160 | extern int __must_check mutex_lock_killable_nested(struct mutex *lock, |
| 161 | unsigned int subclass); |
| 162 | extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass); |
| 163 | |
| 164 | #define mutex_lock(lock) mutex_lock_nested(lock, 0) |
| 165 | #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) |
| 166 | #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) |
| 167 | #define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0) |
| 168 | |
| 169 | #define mutex_lock_nest_lock(lock, nest_lock) \ |
| 170 | do { \ |
| 171 | typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ |
| 172 | _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \ |
| 173 | } while (0) |
| 174 | |
| 175 | #else |
| 176 | extern void mutex_lock(struct mutex *lock); |
| 177 | extern int __must_check mutex_lock_interruptible(struct mutex *lock); |
| 178 | extern int __must_check mutex_lock_killable(struct mutex *lock); |
| 179 | extern void mutex_lock_io(struct mutex *lock); |
| 180 | |
| 181 | # define mutex_lock_nested(lock, subclass) mutex_lock(lock) |
| 182 | # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) |
| 183 | # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) |
| 184 | # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) |
| 185 | # define mutex_lock_io_nested(lock, subclass) mutex_lock(lock) |
| 186 | #endif |
| 187 | |
| 188 | /* |
| 189 | * NOTE: mutex_trylock() follows the spin_trylock() convention, |
| 190 | * not the down_trylock() convention! |
| 191 | * |
| 192 | * Returns 1 if the mutex has been acquired successfully, and 0 on contention. |
| 193 | */ |
| 194 | extern int mutex_trylock(struct mutex *lock); |
| 195 | extern void mutex_unlock(struct mutex *lock); |
| 196 | |
| 197 | extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); |
| 198 | |
| 199 | /* |
| 200 | * These values are chosen such that FAIL and SUCCESS match the |
| 201 | * values of the regular mutex_trylock(). |
| 202 | */ |
| 203 | enum mutex_trylock_recursive_enum { |
| 204 | MUTEX_TRYLOCK_FAILED = 0, |
| 205 | MUTEX_TRYLOCK_SUCCESS = 1, |
| 206 | MUTEX_TRYLOCK_RECURSIVE, |
| 207 | }; |
| 208 | |
| 209 | /** |
| 210 | * mutex_trylock_recursive - trylock variant that allows recursive locking |
| 211 | * @lock: mutex to be locked |
| 212 | * |
| 213 | * This function should not be used, _ever_. It is purely for hysterical GEM |
| 214 | * raisins, and once those are gone this will be removed. |
| 215 | * |
| 216 | * Returns: |
| 217 | * - MUTEX_TRYLOCK_FAILED - trylock failed, |
| 218 | * - MUTEX_TRYLOCK_SUCCESS - lock acquired, |
| 219 | * - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock. |
| 220 | */ |
| 221 | static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum |
| 222 | mutex_trylock_recursive(struct mutex *lock) |
| 223 | { |
| 224 | if (unlikely(__mutex_owner(lock) == current)) |
| 225 | return MUTEX_TRYLOCK_RECURSIVE; |
| 226 | |
| 227 | return mutex_trylock(lock); |
| 228 | } |
| 229 | |
| 230 | #endif /* __LINUX_MUTEX_H */ |