On Mon, Nov 28, 2011 at 10:12:09AM +1030, Alan Modra wrote: > --- libgomp/config/linux/bar.c (revision 181718) > +++ libgomp/config/linux/bar.c (working copy) > @@ -36,18 +36,15 @@ gomp_barrier_wait_end (gomp_barrier_t *b > if (__builtin_expect ((state & 1) != 0, 0)) > { > /* Next time we'll be awaiting TOTAL threads again. */ > - bar->awaited = bar->total; > - atomic_write_barrier (); > - bar->generation += 4; > + __atomic_store_4 (&bar->awaited, bar->total, MEMMODEL_RELEASE); > + __atomic_add_fetch (&bar->generation, 4, MEMMODEL_ACQ_REL); > futex_wake ((int *) &bar->generation, INT_MAX); > }
The above is unfortunate, bar->generation should be only modified from a single thread at this point, but the __atomic_add_fetch will enforce there an atomic instruction on it rather than just some kind of barrier. Jakub