From b1fca26631f76a5e8b18435a43f5d82b8734da4b Mon Sep 17 00:00:00 2001 From: Eric Paris Date: Mon, 23 Mar 2009 18:22:09 +0100 Subject: [PATCH 1/3] mutex: add atomic_dec_and_mutex_lock() Much like the atomic_dec_and_lock() function in which we take an hold a spin_lock if we drop the atomic to 0 this function takes and holds the mutex if we dec the atomic to 0. Signed-off-by: Eric Paris Signed-off-by: Peter Zijlstra Cc: Paul Mackerras Orig-LKML-Reference: <20090323172417.410913479@chello.nl> Signed-off-by: Ingo Molnar --- include/linux/mutex.h | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 3069ec7e0ab8..93054fc3635c 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -151,4 +151,27 @@ extern int __must_check mutex_lock_killable(struct mutex *lock); extern int mutex_trylock(struct mutex *lock); extern void mutex_unlock(struct mutex *lock); +/** + * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 + * @cnt: the atomic which we are to dec + * @lock: the mutex to return holding if we dec to 0 + * + * return true and hold lock if we dec to 0, return false otherwise + */ +static inline int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) +{ + /* dec if we can't possibly hit 0 */ + if (atomic_add_unless(cnt, -1, 1)) + return 0; + /* we might hit 0, so take the lock */ + mutex_lock(lock); + if (!atomic_dec_and_test(cnt)) { + /* when we actually did the dec, we didn't hit 0 */ + mutex_unlock(lock); + return 0; + } + /* we hit 0, and we hold the lock */ + return 1; +} + #endif From 23b94b967f118bef941369238f33c8140be46539 Mon Sep 17 00:00:00 2001 From: Luis Henriques Date: Wed, 29 Apr 2009 21:54:51 +0100 Subject: [PATCH 2/3] locking, rtmutex.c: Documentation cleanup Two minor updates on functions documentation: - Updated documentation for function rt_mutex_unlock(), which contained an incorrect name - Removed extra '*' from comment in function rt_mutex_destroy() [ Impact: cleanup ] Signed-off-by: Luis Henriques Cc: Steven Rostedt LKML-Reference: <20090429205451.GA23154@hades.domain.com> Signed-off-by: Ingo Molnar --- kernel/rtmutex.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c index 69d9cb921ffa..013882e83497 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -864,9 +864,9 @@ int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock, EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); /** - * rt_mutex_lock_interruptible_ktime - lock a rt_mutex interruptible - * the timeout structure is provided - * by the caller + * rt_mutex_timed_lock - lock a rt_mutex interruptible + * the timeout structure is provided + * by the caller * * @lock: the rt_mutex to be locked * @timeout: timeout structure or NULL (no timeout) @@ -913,7 +913,7 @@ void __sched rt_mutex_unlock(struct rt_mutex *lock) } EXPORT_SYMBOL_GPL(rt_mutex_unlock); -/*** +/** * rt_mutex_destroy - mark a mutex unusable * @lock: the mutex to be destroyed * From a511e3f968c462a55ef58697257f5347c73d306e Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Wed, 29 Apr 2009 15:59:58 -0700 Subject: [PATCH 3/3] mutex: add atomic_dec_and_mutex_lock(), fix include/linux/mutex.h:136: warning: 'mutex_lock' declared inline after being called include/linux/mutex.h:136: warning: previous declaration of 'mutex_lock' was here uninline it. [ Impact: clean up and uninline, address compiler warning ] Signed-off-by: Andrew Morton Cc: Al Viro Cc: Christoph Hellwig Cc: Eric Paris Cc: Paul Mackerras Cc: Peter Zijlstra LKML-Reference: <200904292318.n3TNIsi6028340@imap1.linux-foundation.org> Signed-off-by: Ingo Molnar --- include/linux/mutex.h | 24 +----------------------- kernel/mutex.c | 25 ++++++++++++++++++++++++- 2 files changed, 25 insertions(+), 24 deletions(-) diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 93054fc3635c..878cab4f5fcc 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -150,28 +150,6 @@ extern int __must_check mutex_lock_killable(struct mutex *lock); */ extern int mutex_trylock(struct mutex *lock); extern void mutex_unlock(struct mutex *lock); - -/** - * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 - * @cnt: the atomic which we are to dec - * @lock: the mutex to return holding if we dec to 0 - * - * return true and hold lock if we dec to 0, return false otherwise - */ -static inline int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) -{ - /* dec if we can't possibly hit 0 */ - if (atomic_add_unless(cnt, -1, 1)) - return 0; - /* we might hit 0, so take the lock */ - mutex_lock(lock); - if (!atomic_dec_and_test(cnt)) { - /* when we actually did the dec, we didn't hit 0 */ - mutex_unlock(lock); - return 0; - } - /* we hit 0, and we hold the lock */ - return 1; -} +extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); #endif diff --git a/kernel/mutex.c b/kernel/mutex.c index 507cf2b5e9f1..e2d25e9e62ae 100644 --- a/kernel/mutex.c +++ b/kernel/mutex.c @@ -471,5 +471,28 @@ int __sched mutex_trylock(struct mutex *lock) return ret; } - EXPORT_SYMBOL(mutex_trylock); + +/** + * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 + * @cnt: the atomic which we are to dec + * @lock: the mutex to return holding if we dec to 0 + * + * return true and hold lock if we dec to 0, return false otherwise + */ +int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) +{ + /* dec if we can't possibly hit 0 */ + if (atomic_add_unless(cnt, -1, 1)) + return 0; + /* we might hit 0, so take the lock */ + mutex_lock(lock); + if (!atomic_dec_and_test(cnt)) { + /* when we actually did the dec, we didn't hit 0 */ + mutex_unlock(lock); + return 0; + } + /* we hit 0, and we hold the lock */ + return 1; +} +EXPORT_SYMBOL(atomic_dec_and_mutex_lock);