[PATCH v6 4/4] Avoid extra load with CAS in __pthread_mutex_clocklock_common [BZ #28537]
H.J. Lu
hjl.tools@gmail.com
Thu Nov 11 16:24:28 GMT 2021
Replace boolean CAS with value CAS to avoid the extra load.
---
nptl/pthread_mutex_timedlock.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
index 57f3f28869..f763cfc7fa 100644
--- a/nptl/pthread_mutex_timedlock.c
+++ b/nptl/pthread_mutex_timedlock.c
@@ -233,12 +233,12 @@ __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;
--
2.33.1
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