| /* SPDX-License-Identifier: GPL-2.0 */ |
| /* |
| * 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> |
| * |
| * Wait/Die implementation: |
| * Copyright (C) 2013 Canonical Ltd. |
| * Choice of algorithm: |
| * Copyright (C) 2018 WMWare Inc. |
| * |
| * This file contains the main data structure and API definitions. |
| */ |
| |
| #ifndef __LINUX_WW_MUTEX_H |
| #define __LINUX_WW_MUTEX_H |
| |
| #include <linux/mutex.h> |
| #include <linux/rtmutex.h> |
| |
| #if defined(CONFIG_DEBUG_MUTEXES) || \ |
| (defined(CONFIG_PREEMPT_RT) && defined(CONFIG_DEBUG_RT_MUTEXES)) |
| #define DEBUG_WW_MUTEXES |
| #endif |
| |
| #ifndef CONFIG_PREEMPT_RT |
| #define WW_MUTEX_BASE mutex |
| #define ww_mutex_base_init(l,n,k) __mutex_init(l,n,k) |
| #define ww_mutex_base_is_locked(b) mutex_is_locked((b)) |
| #else |
| #define WW_MUTEX_BASE rt_mutex |
| #define ww_mutex_base_init(l,n,k) __rt_mutex_init(l,n,k) |
| #define ww_mutex_base_is_locked(b) rt_mutex_base_is_locked(&(b)->rtmutex) |
| #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; |
| unsigned int is_wait_die; |
| }; |
| |
| struct ww_mutex { |
| struct WW_MUTEX_BASE base; |
| struct ww_acquire_ctx *ctx; |
| #ifdef DEBUG_WW_MUTEXES |
| struct ww_class *ww_class; |
| #endif |
| }; |
| |
| struct ww_acquire_ctx { |
| struct task_struct *task; |
| unsigned long stamp; |
| unsigned int acquired; |
| unsigned short wounded; |
| unsigned short is_wait_die; |
| #ifdef DEBUG_WW_MUTEXES |
| unsigned int done_acquire; |
| struct ww_class *ww_class; |
| void *contending_lock; |
| #endif |
| #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| struct lockdep_map dep_map; |
| #endif |
| #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH |
| unsigned int deadlock_inject_interval; |
| unsigned int deadlock_inject_countdown; |
| #endif |
| }; |
| |
| #define __WW_CLASS_INITIALIZER(ww_class, _is_wait_die) \ |
| { .stamp = ATOMIC_LONG_INIT(0) \ |
| , .acquire_name = #ww_class "_acquire" \ |
| , .mutex_name = #ww_class "_mutex" \ |
| , .is_wait_die = _is_wait_die } |
| |
| #define DEFINE_WD_CLASS(classname) \ |
| struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 1) |
| |
| #define DEFINE_WW_CLASS(classname) \ |
| struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 0) |
| |
| /** |
| * 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. Static define macro for w/w mutex is not provided and this function |
| * is the only way to properly initialize the w/w mutex. |
| * |
| * 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) |
| { |
| ww_mutex_base_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); |
| lock->ctx = NULL; |
| #ifdef DEBUG_WW_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/die 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_relaxed(&ww_class->stamp); |
| ctx->acquired = 0; |
| ctx->wounded = false; |
| ctx->is_wait_die = ww_class->is_wait_die; |
| #ifdef DEBUG_WW_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 DEBUG_WW_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_LOCK_ALLOC |
| mutex_release(&ctx->dep_map, _THIS_IP_); |
| #endif |
| #ifdef DEBUG_WW_MUTEXES |
| DEBUG_LOCKS_WARN_ON(ctx->acquired); |
| if (!IS_ENABLED(CONFIG_PROVE_LOCKING)) |
| /* |
| * lockdep will normally handle this, |
| * but fail without anyway |
| */ |
| ctx->done_acquire = 1; |
| |
| if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC)) |
| /* ensure ww_acquire_fini will still fail if called twice */ |
| ctx->acquired = ~0U; |
| #endif |
| } |
| |
| /** |
| * 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/die algorithm. If the lock isn't immediately available this function |
| * will either sleep until it is (wait case). Or it selects the current context |
| * for backing off by returning -EDEADLK (die 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 die 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. |
| */ |
| extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); |
| |
| /** |
| * 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/die algorithm. If the lock isn't immediately available this function |
| * will either sleep until it is (wait case). Or it selects the current context |
| * for backing off by returning -EDEADLK (die 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 die 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. |
| */ |
| extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, |
| struct ww_acquire_ctx *ctx); |
| |
| /** |
| * 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 die 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 DEBUG_WW_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 die 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 DEBUG_WW_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); |
| |
| extern int __must_check ww_mutex_trylock(struct ww_mutex *lock, |
| struct ww_acquire_ctx *ctx); |
| |
| /*** |
| * 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) |
| { |
| #ifndef CONFIG_PREEMPT_RT |
| mutex_destroy(&lock->base); |
| #endif |
| } |
| |
| /** |
| * 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 ww_mutex_base_is_locked(&lock->base); |
| } |
| |
| #endif |