From: Eric Paris <[email protected]>
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 <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
CC: Paul Mackerras <[email protected]>
---
include/linux/mutex.h | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
Index: linux-2.6/include/linux/mutex.h
===================================================================
--- linux-2.6.orig/include/linux/mutex.h
+++ linux-2.6/include/linux/mutex.h
@@ -151,4 +151,27 @@ extern int __must_check mutex_lock_killa
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
--
Commit-ID: 3a2d367d9aabac486ac4444c6c7ec7a1dab16267
Gitweb: http://git.kernel.org/tip/3a2d367d9aabac486ac4444c6c7ec7a1dab16267
Author: Eric Paris <[email protected]>
AuthorDate: Mon, 23 Mar 2009 18:22:09 +0100
Committer: Ingo Molnar <[email protected]>
CommitDate: Mon, 23 Mar 2009 21:45:10 +0100
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 <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Paul Mackerras <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
---
include/linux/mutex.h | 23 +++++++++++++++++++++++
1 files changed, 23 insertions(+), 0 deletions(-)
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 3069ec7..93054fc 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
Commit-ID: 655be4a209fbcae85a745027f426e1f9879b5648
Gitweb: http://git.kernel.org/tip/655be4a209fbcae85a745027f426e1f9879b5648
Author: H. Peter Anvin <[email protected]>
AuthorDate: Wed, 1 Apr 2009 17:21:56 -0700
Committer: H. Peter Anvin <[email protected]>
CommitDate: Wed, 1 Apr 2009 17:21:56 -0700
mutex: drop "inline" from mutex_lock() inside kernel/mutex.c
Impact: build fix
mutex_lock() is was defined inline in kernel/mutex.c, but wasn't
declared so not in <linux/mutex.h>. This didn't cause a problem until
checkin 3a2d367d9aabac486ac4444c6c7ec7a1dab16267 added the
atomic_dec_and_mutex_lock() inline in between declaration and
definion.
This broke building with CONFIG_ALLOW_WARNINGS=n, e.g. make
allnoconfig.
Either from the source code nor the allnoconfig binary output I cannot
find any internal references to mutex_lock() in kernel/mutex.c, so
presumably this "inline" is now-useless legacy.
Cc: Eric Paris <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Paul Mackerras <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
---
kernel/mutex.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/mutex.c b/kernel/mutex.c
index e1fb735..29758eb 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -89,7 +89,7 @@ __mutex_lock_slowpath(atomic_t *lock_count);
*
* This function is similar to (but not equivalent to) down().
*/
-void inline __sched mutex_lock(struct mutex *lock)
+void __sched mutex_lock(struct mutex *lock)
{
might_sleep();
/*