diff options
| -rw-r--r-- | include/linux/mutex.h | 358 | ||||
| -rw-r--r-- | include/linux/reservation.h | 2 | ||||
| -rw-r--r-- | include/linux/ww_mutex.h | 378 | ||||
| -rw-r--r-- | kernel/mutex.c | 1 | ||||
| -rw-r--r-- | lib/locking-selftest.c | 1 |
5 files changed, 381 insertions, 359 deletions
diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 3793ed7feeeb..ccd4260834c5 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -78,40 +78,6 @@ struct mutex_waiter { #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 <linux/mutex-debug.h> #else @@ -136,11 +102,8 @@ static inline void mutex_destroy(struct mutex *lock) {} #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) \ @@ -150,49 +113,13 @@ static inline void mutex_destroy(struct mutex *lock) {} __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 * @@ -246,291 +173,6 @@ extern int __must_check mutex_lock_killable(struct mutex *lock); 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 diff --git a/include/linux/reservation.h b/include/linux/reservation.h index e9ee806a9d72..813dae960ebd 100644 --- a/include/linux/reservation.h +++ b/include/linux/reservation.h @@ -39,7 +39,7 @@ #ifndef _LINUX_RESERVATION_H #define _LINUX_RESERVATION_H -#include <linux/mutex.h> +#include <linux/ww_mutex.h> extern struct ww_class reservation_ww_class; diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h new file mode 100644 index 000000000000..760399a470bd --- /dev/null +++ b/include/linux/ww_mutex.h @@ -0,0 +1,378 @@ +/* + * Wound/Wait Mutexes: blocking mutual exclusion locks with deadlock avoidance + * + * Original mutex implementation started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> + * + * Wound/wait implementation: + * Copyright (C) 2013 Canonical Ltd. + * + * This file contains the main data structure and API definitions. + */ + +#ifndef __LINUX_WW_MUTEX_H +#define __LINUX_WW_MUTEX_H + +#include <linux/mutex.h> + +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_LOCK_ALLOC +# define __WW_CLASS_MUTEX_INITIALIZER(lockname, ww_class) \ + , .ww_class = &ww_class +#else +# define __WW_CLASS_MUTEX_INITIALIZER(lockname, ww_class) +#endif + +#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_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) + +/** + * 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 +} + +/** + * 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); + + 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); +} + +#endif diff --git a/kernel/mutex.c b/kernel/mutex.c index e581ada5faf4..ff05f4bd86eb 100644 --- a/kernel/mutex.c +++ b/kernel/mutex.c @@ -18,6 +18,7 @@ * Also see Documentation/mutex-design.txt. */ #include <linux/mutex.h> +#include <linux/ww_mutex.h> #include <linux/sched.h> #include <linux/sched/rt.h> #include <linux/export.h> diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index aad024dde3c4..6dc09d8f4c24 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -12,6 +12,7 @@ */ #include <linux/rwsem.h> #include <linux/mutex.h> +#include <linux/ww_mutex.h> #include <linux/sched.h> #include <linux/delay.h> #include <linux/lockdep.h> |