Avoid extra load with CAS in __pthread_mutex_clocklock_common [BZ #28537]

Replace boolean CAS with value CAS to avoid the extra load.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
(cherry picked from commit 49302b8fdf9103b6fc0a398678668a22fa19574c)

diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
index 11ad7005d07afc6eb06d912709d8fd2d61cb3da5..90cede9446e33fcf1cf8a9ea6c425399398c463a 100644 (file)
--- a/nptl/pthread_mutex_timedlock.c
+++ b/nptl/pthread_mutex_timedlock.c
@@ -234,12 +234,12 @@ __pthread_mutex_clocklock_common (pthread_mutex_t *mutex,
             meantime.  */
          if ((oldval & FUTEX_WAITERS) == 0)
            {
-             if (atomic_compare_and_exchange_bool_acq (&mutex->__data.__lock,
-                                                       oldval | FUTEX_WAITERS,
-                                                       oldval)
-                 != 0)
+             int val;
+             if ((val = atomic_compare_and_exchange_val_acq
+                  (&mutex->__data.__lock, oldval | FUTEX_WAITERS,
+                   oldval)) != oldval)
                {
-                 oldval = mutex->__data.__lock;
+                 oldval = val;
                  continue;
                }
              oldval |= FUTEX_WAITERS;