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authorLinus Torvalds <torvalds@linux-foundation.org>2013-07-13 15:35:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-13 15:35:12 -0700
commit4fa109b13042868de84bedc70ea9b8337b502cf9 (patch)
treee82ebb56e8b9316d5d7e3561523db0c8bcd42946
parent9663398a094e3b85415e27fe6047b067f5f81f99 (diff)
parent1b375dc30710180c4b88cc59caba6e3481ec5c8b (diff)
downloadlinux-4fa109b13042868de84bedc70ea9b8337b502cf9.tar.gz
Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core locking updates from Thomas Gleixner: "Header cleanup as requested by Linus" (This is the "don't include support for ww_mutex in a header file that everybody wants, when almost nobody wants the ww part" change) * 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: mutex: Move ww_mutex definitions to ww_mutex.h
-rw-r--r--include/linux/mutex.h358
-rw-r--r--include/linux/reservation.h2
-rw-r--r--include/linux/ww_mutex.h378
-rw-r--r--kernel/mutex.c1
-rw-r--r--lib/locking-selftest.c1
5 files changed, 381 insertions, 359 deletions
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 3793ed7feee..ccd4260834c 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 e9ee806a9d7..813dae960eb 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 00000000000..760399a470b
--- /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 e581ada5faf..ff05f4bd86e 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 aad024dde3c..6dc09d8f4c2 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>