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

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

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>

diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
index 2bd41767e0490bff13f338448f25a8ae9cd47633..59a28cff1aaef91433da66e7dab9d479867fdd17 100644 (file)
--- a/nptl/pthread_mutex_lock.c
+++ b/nptl/pthread_mutex_lock.c
@@ -297,12 +297,12 @@ __pthread_mutex_lock_full (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;