https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102566
--- Comment #28 from Hongtao.liu <crazylht at gmail dot com> ---
Can be optimize
int gomp_futex_wake = FUTEX_WAKE | FUTEX_PRIVATE_FLAG;
int gomp_futex_wait = FUTEX_WAIT | FUTEX_PRIVATE_FLAG;
void
gomp_mutex_lock_slow (gomp_mutex_t *mutex, int oldval)
{
/* First loop spins a while. */
while (oldval == 1)
{
if (do_spin (mutex, 1))
{
/* Spin timeout, nothing changed. Set waiting flag. */
oldval = __atomic_exchange_n (mutex, -1, MEMMODEL_ACQUIRE);
if (oldval == 0)
return;
futex_wait (mutex, -1);
break;
}
else
{
/* Something changed. If now unlocked, we're good to go. */
oldval = 0;
if (__atomic_compare_exchange_n (mutex, &oldval, 1, false,
MEMMODEL_ACQUIRE, MEMMODEL_RELAXED))
return;
}
}
/* Second loop waits until mutex is unlocked. We always exit this
loop with wait flag set, so next unlock will awaken a thread. */
while ((oldval = __atomic_exchange_n (mutex, -1, MEMMODEL_ACQUIRE)))
do_wait (mutex, -1);
}
with _atomic_fetch_or/and/xor ?
