diff options
Diffstat (limited to 'libgomp/config/linux/mutex.c')
| -rw-r--r-- | libgomp/config/linux/mutex.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/libgomp/config/linux/mutex.c b/libgomp/config/linux/mutex.c index 2574f7b..1b84ffb 100644 --- a/libgomp/config/linux/mutex.c +++ b/libgomp/config/linux/mutex.c @@ -34,25 +34,32 @@ long 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)) { - oldval = __sync_lock_test_and_set (mutex, 2); + /* Spin timeout, nothing changed. Set waiting flag. */ + oldval = __atomic_exchange_n (mutex, -1, MEMMODEL_ACQUIRE); if (oldval == 0) return; - futex_wait (mutex, 2); + futex_wait (mutex, -1); break; } else { - oldval = __sync_val_compare_and_swap (mutex, 0, 1); - if (oldval == 0) + /* 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; } } - while ((oldval = __sync_lock_test_and_set (mutex, 2))) - do_wait (mutex, 2); + + /* 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); } void |