/* * Mutexes: blocking mutual exclusion locks * * started by Ingo Molnar: * * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar * * This file contains the main data structure and API definitions. */ #ifndef __LINUX_MUTEX_H #define __LINUX_MUTEX_H #include #include #include #include #include #include /* * Simple, straightforward mutexes with strict semantics: * * - only one task can hold the mutex at a time * - only the owner can unlock the mutex * - multiple unlocks are not permitted * - recursive locking is not permitted * - a mutex object must be initialized via the API * - a mutex object must not be initialized via memset or copying * - task may not exit with mutex held * - memory areas where held locks reside must not be freed * - held mutexes must not be reinitialized * - mutexes may not be used in hardware or software interrupt * contexts such as tasklets and timers * * These semantics are fully enforced when DEBUG_MUTEXES is * enabled. Furthermore, besides enforcing the above rules, the mutex * debugging code also implements a number of additional features * that make lock debugging easier and faster: * * - uses symbolic names of mutexes, whenever they are printed in debug output * - point-of-acquire tracking, symbolic lookup of function names * - list of all locks held in the system, printout of them * - owner tracking * - detects self-recursing locks and prints out all relevant info * - detects multi-task circular deadlocks and prints out all affected * locks and tasks (and only those tasks) */ struct mutex { /* 1: unlocked, 0: locked, negative: locked, possible waiters */ atomic_t count; spinlock_t wait_lock; struct list_head wait_list; #if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP) struct task_struct *owner; #endif #ifdef CONFIG_MUTEX_SPIN_ON_OWNER void *spin_mlock; /* Spinner MCS lock */ #endif #ifdef CONFIG_DEBUG_MUTEXES const char *name; void *magic; #endif #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif }; /* * This is the control structure for tasks blocked on mutex, * which resides on the blocked task's kernel stack: */ struct mutex_waiter { struct list_head list; struct task_struct *task; #ifdef CONFIG_DEBUG_MUTEXES void *magic; #endif }; struct ww_class { atomic_long_t stamp; struct lock_class_key acquire_key; struct lock_class_key mutex_key; const char *acquire_name; const char *mutex_name; }; struct ww_acquire_ctx { struct task_struct *task; unsigned long stamp; unsigned acquired; #ifdef CONFIG_DEBUG_MUTEXES unsigned done_acquire; struct ww_class *ww_class; struct ww_mutex *contending_lock; #endif #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH unsigned deadlock_inject_interval; unsigned deadlock_inject_countdown; #endif }; struct ww_mutex { struct mutex base; struct ww_acquire_ctx *ctx; #ifdef CONFIG_DEBUG_MUTEXES struct ww_class *ww_class; #endif }; #ifdef CONFIG_DEBUG_MUTEXES # include #else # define __DEBUG_MUTEX_INITIALIZER(lockname) /** * mutex_init - initialize the mutex * @mutex: the mutex to be initialized * * Initialize the mutex to unlocked state. * * It is not allowed to initialize an already locked mutex. */ # define mutex_init(mutex) \ do { \ static struct lock_class_key __key; \ \ __mutex_init((mutex), #mutex, &__key); \ } while (0) static inline void mutex_destroy(struct mutex *lock) {} #endif #ifdef CONFIG_DEBUG_LOCK_ALLOC # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ , .dep_map = { .name = #lockname } # define __WW_CLASS_MUTEX_INITIALIZER(lockname, ww_class) \ , .ww_class = &ww_class #else # define __DEP_MAP_MUTEX_INITIALIZER(lockname) # define __WW_CLASS_MUTEX_INITIALIZER(lockname, ww_class) #endif #define __MUTEX_INITIALIZER(lockname) \ { .count = ATOMIC_INIT(1) \ , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \ , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \ __DEBUG_MUTEX_INITIALIZER(lockname) \ __DEP_MAP_MUTEX_INITIALIZER(lockname) } #define __WW_CLASS_INITIALIZER(ww_class) \ { .stamp = ATOMIC_LONG_INIT(0) \ , .acquire_name = #ww_class "_acquire" \ , .mutex_name = #ww_class "_mutex" } #define __WW_MUTEX_INITIALIZER(lockname, class) \ { .base = { \__MUTEX_INITIALIZER(lockname) } \ __WW_CLASS_MUTEX_INITIALIZER(lockname, class) } #define DEFINE_MUTEX(mutexname) \ struct mutex mutexname = __MUTEX_INITIALIZER(mutexname) #define DEFINE_WW_CLASS(classname) \ struct ww_class classname = __WW_CLASS_INITIALIZER(classname) #define DEFINE_WW_MUTEX(mutexname, ww_class) \ struct ww_mutex mutexname = __WW_MUTEX_INITIALIZER(mutexname, ww_class) extern void __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key); /** * ww_mutex_init - initialize the w/w mutex * @lock: the mutex to be initialized * @ww_class: the w/w class the mutex should belong to * * Initialize the w/w mutex to unlocked state and associate it with the given * class. * * It is not allowed to initialize an already locked mutex. */ static inline void ww_mutex_init(struct ww_mutex *lock, struct ww_class *ww_class) { __mutex_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); lock->ctx = NULL; #ifdef CONFIG_DEBUG_MUTEXES lock->ww_class = ww_class; #endif } /** * mutex_is_locked - is the mutex locked * @lock: the mutex to be queried * * Returns 1 if the mutex is locked, 0 if unlocked. */ static inline int mutex_is_locked(struct mutex *lock) { return atomic_read(&lock->count) != 1; } /* * See kernel/mutex.c for detailed documentation of these APIs. * Also see Documentation/mutex-design.txt. */ #ifdef CONFIG_DEBUG_LOCK_ALLOC extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass); extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock); extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass); extern int __must_check mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass); #define mutex_lock(lock) mutex_lock_nested(lock, 0) #define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0) #define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0) #define mutex_lock_nest_lock(lock, nest_lock) \ do { \ typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \ _mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \ } while (0) #else extern void mutex_lock(struct mutex *lock); extern int __must_check mutex_lock_interruptible(struct mutex *lock); extern int __must_check mutex_lock_killable(struct mutex *lock); # define mutex_lock_nested(lock, subclass) mutex_lock(lock) # define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock) # define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock) # define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock) #endif /* * NOTE: mutex_trylock() follows the spin_trylock() convention, * not the down_trylock() convention! * * Returns 1 if the mutex has been acquired successfully, and 0 on contention. */ extern int mutex_trylock(struct mutex *lock); extern void mutex_unlock(struct mutex *lock); /** * ww_acquire_init - initialize a w/w acquire context * @ctx: w/w acquire context to initialize * @ww_class: w/w class of the context * * Initializes an context to acquire multiple mutexes of the given w/w class. * * Context-based w/w mutex acquiring can be done in any order whatsoever within * a given lock class. Deadlocks will be detected and handled with the * wait/wound logic. * * Mixing of context-based w/w mutex acquiring and single w/w mutex locking can * result in undetected deadlocks and is so forbidden. Mixing different contexts * for the same w/w class when acquiring mutexes can also result in undetected * deadlocks, and is hence also forbidden. Both types of abuse will be caught by * enabling CONFIG_PROVE_LOCKING. * * Nesting of acquire contexts for _different_ w/w classes is possible, subject * to the usual locking rules between different lock classes. * * An acquire context must be released with ww_acquire_fini by the same task * before the memory is freed. It is recommended to allocate the context itself * on the stack. */ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, struct ww_class *ww_class) { ctx->task = current; ctx->stamp = atomic_long_inc_return(&ww_class->stamp); ctx->acquired = 0; #ifdef CONFIG_DEBUG_MUTEXES ctx->ww_class = ww_class; ctx->done_acquire = 0; ctx->contending_lock = NULL; #endif #ifdef CONFIG_DEBUG_LOCK_ALLOC debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, &ww_class->acquire_key, 0); mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); #endif #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH ctx->deadlock_inject_interval = 1; ctx->deadlock_inject_countdown = ctx->stamp & 0xf; #endif } /** * ww_acquire_done - marks the end of the acquire phase * @ctx: the acquire context * * Marks the end of the acquire phase, any further w/w mutex lock calls using * this context are forbidden. * * Calling this function is optional, it is just useful to document w/w mutex * code and clearly designated the acquire phase from actually using the locked * data structures. */ static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) { #ifdef CONFIG_DEBUG_MUTEXES lockdep_assert_held(ctx); DEBUG_LOCKS_WARN_ON(ctx->done_acquire); ctx->done_acquire = 1; #endif } /** * ww_acquire_fini - releases a w/w acquire context * @ctx: the acquire context to free * * Releases a w/w acquire context. This must be called _after_ all acquired w/w * mutexes have been released with ww_mutex_unlock. */ static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) { #ifdef CONFIG_DEBUG_MUTEXES mutex_release(&ctx->dep_map, 0, _THIS_IP_); DEBUG_LOCKS_WARN_ON(ctx->acquired); if (!config_enabled(CONFIG_PROVE_LOCKING)) /* * lockdep will normally handle this, * but fail without anyway */ ctx->done_acquire = 1; if (!config_enabled(CONFIG_DEBUG_LOCK_ALLOC)) /* ensure ww_acquire_fini will still fail if called twice */ ctx->acquired = ~0U; #endif } extern int __must_check __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); extern int __must_check __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); /** * ww_mutex_lock - acquire the w/w mutex * @lock: the mutex to be acquired * @ctx: w/w acquire context, or NULL to acquire only a single lock. * * Lock the w/w mutex exclusively for this task. * * Deadlocks within a given w/w class of locks are detected and handled with the * wait/wound algorithm. If the lock isn't immediately avaiable this function * will either sleep until it is (wait case). Or it selects the current context * for backing off by returning -EDEADLK (wound case). Trying to acquire the * same lock with the same context twice is also detected and signalled by * returning -EALREADY. Returns 0 if the mutex was successfully acquired. * * In the wound case the caller must release all currently held w/w mutexes for * the given context and then wait for this contending lock to be available by * calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this * lock and proceed with trying to acquire further w/w mutexes (e.g. when * scanning through lru lists trying to free resources). * * The mutex must later on be released by the same task that * acquired it. The task may not exit without first unlocking the mutex. Also, * kernel memory where the mutex resides must not be freed with the mutex still * locked. The mutex must first be initialized (or statically defined) before it * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be * of the same w/w lock class as was used to initialize the acquire context. * * A mutex acquired with this function must be released with ww_mutex_unlock. */ static inline int ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) { if (ctx) return __ww_mutex_lock(lock, ctx); else { mutex_lock(&lock->base); return 0; } } /** * ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible * @lock: the mutex to be acquired * @ctx: w/w acquire context * * Lock the w/w mutex exclusively for this task. * * Deadlocks within a given w/w class of locks are detected and handled with the * wait/wound algorithm. If the lock isn't immediately avaiable this function * will either sleep until it is (wait case). Or it selects the current context * for backing off by returning -EDEADLK (wound case). Trying to acquire the * same lock with the same context twice is also detected and signalled by * returning -EALREADY. Returns 0 if the mutex was successfully acquired. If a * signal arrives while waiting for the lock then this function returns -EINTR. * * In the wound case the caller must release all currently held w/w mutexes for * the given context and then wait for this contending lock to be available by * calling ww_mutex_lock_slow_interruptible. Alternatively callers can opt to * not acquire this lock and proceed with trying to acquire further w/w mutexes * (e.g. when scanning through lru lists trying to free resources). * * The mutex must later on be released by the same task that * acquired it. The task may not exit without first unlocking the mutex. Also, * kernel memory where the mutex resides must not be freed with the mutex still * locked. The mutex must first be initialized (or statically defined) before it * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be * of the same w/w lock class as was used to initialize the acquire context. * * A mutex acquired with this function must be released with ww_mutex_unlock. */ static inline int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) { if (ctx) return __ww_mutex_lock_interruptible(lock, ctx); else return mutex_lock_interruptible(&lock->base); } /** * ww_mutex_lock_slow - slowpath acquiring of the w/w mutex * @lock: the mutex to be acquired * @ctx: w/w acquire context * * Acquires a w/w mutex with the given context after a wound case. This function * will sleep until the lock becomes available. * * The caller must have released all w/w mutexes already acquired with the * context and then call this function on the contended lock. * * Afterwards the caller may continue to (re)acquire the other w/w mutexes it * needs with ww_mutex_lock. Note that the -EALREADY return code from * ww_mutex_lock can be used to avoid locking this contended mutex twice. * * It is forbidden to call this function with any other w/w mutexes associated * with the context held. It is forbidden to call this on anything else than the * contending mutex. * * Note that the slowpath lock acquiring can also be done by calling * ww_mutex_lock directly. This function here is simply to help w/w mutex * locking code readability by clearly denoting the slowpath. */ static inline void ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) { int ret; #ifdef CONFIG_DEBUG_MUTEXES DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); #endif ret = ww_mutex_lock(lock, ctx); (void)ret; } /** * ww_mutex_lock_slow_interruptible - slowpath acquiring of the w/w mutex, * interruptible * @lock: the mutex to be acquired * @ctx: w/w acquire context * * Acquires a w/w mutex with the given context after a wound case. This function * will sleep until the lock becomes available and returns 0 when the lock has * been acquired. If a signal arrives while waiting for the lock then this * function returns -EINTR. * * The caller must have released all w/w mutexes already acquired with the * context and then call this function on the contended lock. * * Afterwards the caller may continue to (re)acquire the other w/w mutexes it * needs with ww_mutex_lock. Note that the -EALREADY return code from * ww_mutex_lock can be used to avoid locking this contended mutex twice. * * It is forbidden to call this function with any other w/w mutexes associated * with the given context held. It is forbidden to call this on anything else * than the contending mutex. * * Note that the slowpath lock acquiring can also be done by calling * ww_mutex_lock_interruptible directly. This function here is simply to help * w/w mutex locking code readability by clearly denoting the slowpath. */ static inline int __must_check ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) { #ifdef CONFIG_DEBUG_MUTEXES DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); #endif return ww_mutex_lock_interruptible(lock, ctx); } extern void ww_mutex_unlock(struct ww_mutex *lock); /** * ww_mutex_trylock - tries to acquire the w/w mutex without acquire context * @lock: mutex to lock * * Trylocks a mutex without acquire context, so no deadlock detection is * possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise. */ static inline int __must_check ww_mutex_trylock(struct ww_mutex *lock) { return mutex_trylock(&lock->base); } /*** * ww_mutex_destroy - mark a w/w mutex unusable * @lock: the mutex to be destroyed * * This function marks the mutex uninitialized, and any subsequent * use of the mutex is forbidden. The mutex must not be locked when * this function is called. */ static inline void ww_mutex_destroy(struct ww_mutex *lock) { mutex_destroy(&lock->base); } /** * ww_mutex_is_locked - is the w/w mutex locked * @lock: the mutex to be queried * * Returns 1 if the mutex is locked, 0 if unlocked. */ static inline bool ww_mutex_is_locked(struct ww_mutex *lock) { return mutex_is_locked(&lock->base); } extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); #ifndef CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX #define arch_mutex_cpu_relax() cpu_relax() #endif #endif