core kernel fix

GIT PULL Ingo Molnar 1 participant 1 message Aug 20, 2012 Generic include/asm header files

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Ingo Molnar

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2012-08-20 09:01 UTC #0 lore raw

Linus,

Please pull the latest core-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-urgent-for-linus

HEAD: 0bce9c46bf3b15f485d82d7e81dabed6ebcc24b1 mutex: Place lock in contended state after fastpath_lock failure

Thanks,

Ingo

------------------>
Will Deacon (1):
mutex: Place lock in contended state after fastpath_lock failure

 include/asm-generic/mutex-xchg.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

include/asm-generic/mutex-xchg.h +9 -2

index 580a6d3..c04e0db 100644
@@ -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;
 }