diff options
Diffstat (limited to 'nptl/pthread_once.c')
| -rw-r--r-- | nptl/pthread_once.c | 23 |
1 files changed, 9 insertions, 14 deletions
diff --git a/nptl/pthread_once.c b/nptl/pthread_once.c index 05aea84d38..9bb82e9382 100644 --- a/nptl/pthread_once.c +++ b/nptl/pthread_once.c @@ -34,7 +34,7 @@ clear_once_control (void *arg) other threads that see this value: This function will be called if we get interrupted (see __pthread_once), so all we need to relay to other threads is the state being reset again. */ - *once_control = 0; + atomic_store_relaxed (once_control, 0); lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE); } @@ -68,20 +68,18 @@ __pthread_once_slow (pthread_once_t *once_control, void (*init_routine) (void)) { while (1) { - int oldval, val, newval; + int val, newval; /* We need acquire memory order for this load because if the value signals that initialization has finished, we need to see any data modifications done during initialization. */ - val = *once_control; - atomic_read_barrier (); + val = atomic_load_acquire (once_control); do { /* Check if the initialization has already been done. */ if (__glibc_likely ((val & __PTHREAD_ONCE_DONE) != 0)) return 0; - oldval = val; /* We try to set the state to in-progress and having the current fork generation. We don't need atomic accesses for the fork generation because it's immutable in a particular process, and @@ -90,18 +88,17 @@ __pthread_once_slow (pthread_once_t *once_control, void (*init_routine) (void)) newval = __fork_generation | __PTHREAD_ONCE_INPROGRESS; /* We need acquire memory order here for the same reason as for the load from once_control above. */ - val = atomic_compare_and_exchange_val_acq (once_control, newval, - oldval); } - while (__glibc_unlikely (val != oldval)); + while (__glibc_unlikely (!atomic_compare_exchange_weak_acquire ( + once_control, &val, newval))); /* Check if another thread already runs the initializer. */ - if ((oldval & __PTHREAD_ONCE_INPROGRESS) != 0) + if ((val & __PTHREAD_ONCE_INPROGRESS) != 0) { /* Check whether the initializer execution was interrupted by a fork. We know that for both values, __PTHREAD_ONCE_INPROGRESS is set and __PTHREAD_ONCE_DONE is not. */ - if (oldval == newval) + if (val == newval) { /* Same generation, some other thread was faster. Wait. */ lll_futex_wait (once_control, newval, LLL_PRIVATE); @@ -122,8 +119,7 @@ __pthread_once_slow (pthread_once_t *once_control, void (*init_routine) (void)) /* Mark *once_control as having finished the initialization. We need release memory order here because we need to synchronize with other threads that want to use the initialized data. */ - atomic_write_barrier (); - *once_control = __PTHREAD_ONCE_DONE; + atomic_store_release (once_control, __PTHREAD_ONCE_DONE); /* Wake up all other threads. */ lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE); @@ -138,8 +134,7 @@ __pthread_once (pthread_once_t *once_control, void (*init_routine) (void)) { /* Fast path. See __pthread_once_slow. */ int val; - val = *once_control; - atomic_read_barrier (); + val = atomic_load_acquire (once_control); if (__glibc_likely ((val & __PTHREAD_ONCE_DONE) != 0)) return 0; else |