The patch titled
mutex: add atomic_dec_and_mutex_lock
has been added to the -mm tree. Its filename is
mutex-add-atomic_dec_and_mutex_lock.patch
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Subject: mutex: add atomic_dec_and_mutex_lock
From: Eric Paris <eparis@xxxxxxxxxx>
Much like the atomic_dec_and_lock() function in which we take and 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 <eparis@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mutex.h | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff -puN include/linux/mutex.h~mutex-add-atomic_dec_and_mutex_lock include/linux/mutex.h
--- a/include/linux/mutex.h~mutex-add-atomic_dec_and_mutex_lock
+++ a/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
_
Patches currently in -mm which might be from eparis@xxxxxxxxxx are
linux-next.patch
mutex-add-atomic_dec_and_mutex_lock.patch
fsnotify-unified-filesystem-notification-backend.patch
fsnotify-add-marks-to-inodes-so-groups-can-interpret-how-to-handle-those-inodes.patch
fsnotify-parent-event-notification.patch
dnotify-reimplement-dnotify-using-fsnotify.patch
fsnotify-generic-notification-queue-and-waitq.patch
fsnotify-include-pathnames-with-entries-when-possible.patch
fsnotify-add-correlations-between-events.patch
fsnotify-allow-groups-to-add-private-data-to-events.patch
fsnotify-fsnotify-marks-on-inodes-pin-them-in-core.patch
fsnotify-handle-filesystem-unmounts-with-fsnotify-marks.patch
inotify-reimplement-inotify-using-fsnotify.patch
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