Merge branch 'locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
spinlock: Add missing __raw_spin_lock_flags() stub for UP
mutex: add atomic_dec_and_mutex_lock(), fix
locking, rtmutex.c: Documentation cleanup
mutex: add atomic_dec_and_mutex_lock()
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 3069ec7..878cab4 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -150,5 +150,6 @@
*/
extern int mutex_trylock(struct mutex *lock);
extern void mutex_unlock(struct mutex *lock);
+extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
#endif
diff --git a/include/linux/spinlock_up.h b/include/linux/spinlock_up.h
index 938234c..d4841ed 100644
--- a/include/linux/spinlock_up.h
+++ b/include/linux/spinlock_up.h
@@ -60,6 +60,7 @@
#define __raw_spin_is_locked(lock) ((void)(lock), 0)
/* for sched.c and kernel_lock.c: */
# define __raw_spin_lock(lock) do { (void)(lock); } while (0)
+# define __raw_spin_lock_flags(lock, flags) do { (void)(lock); } while (0)
# define __raw_spin_unlock(lock) do { (void)(lock); } while (0)
# define __raw_spin_trylock(lock) ({ (void)(lock); 1; })
#endif /* DEBUG_SPINLOCK */
diff --git a/kernel/mutex.c b/kernel/mutex.c
index 6ca5fe9..e5cc0cd 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -473,5 +473,28 @@
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);
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index fec77e7..820c5af 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -891,9 +891,9 @@
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)
@@ -940,7 +940,7 @@
}
EXPORT_SYMBOL_GPL(rt_mutex_unlock);
-/***
+/**
* rt_mutex_destroy - mark a mutex unusable
* @lock: the mutex to be destroyed
*
