Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

Pull a mutex fix from Ingo Molnar.

Fix the fastpath_lock failure contention flag for xchg-based mutexes.

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  mutex: Place lock in contended state after fastpath_lock failure

diff --git a/include/asm-generic/mutex-xchg.h b/include/asm-generic/mutex-xchg.h
index 580a6d3..c04e0db 100644 (file)
--- a/include/asm-generic/mutex-xchg.h
+++ b/include/asm-generic/mutex-xchg.h
@@ -26,7 +26,13 @@ static inline void
 __mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
 {
        if (unlikely(atomic_xchg(count, 0) != 1))
-               fail_fn(count);
+               /*
+                * We failed to acquire the lock, so mark it contended
+                * to ensure that any waiting tasks are woken up by the
+                * unlock slow path.
+                */
+               if (likely(atomic_xchg(count, -1) != 1))
+                       fail_fn(count);
 }
 
 /**
@@ -43,7 +49,8 @@ static inline int
 __mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
 {
        if (unlikely(atomic_xchg(count, 0) != 1))
-               return fail_fn(count);
+               if (likely(atomic_xchg(count, -1) != 1))
+                       return fail_fn(count);
        return 0;
 }