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Release 4.7 include/linux/ww_mutex.h

Directory: include/linux
/*
 * 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 }

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/** * 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 }

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/** * 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 }

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/** * 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 }

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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; }

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/** * 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); }

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/** * 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; }

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/** * 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); }

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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); }

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/*** * 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); }

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/** * 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); }

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#endif

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Directory: include/linux
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