On Mon, Nov 28, 2011 at 09:13:27AM +0100, Jakub Jelinek wrote:
> 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.
I will try without the atomic add and see what happens.
--
Alan Modra
Australia Development Lab, IBM
