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Re: Fix PR51298, libgomp barrier failure
On 11/28/2011 06:02 AM, Alan Modra wrote:
> - unsigned int ret = bar->generation & ~3;
> - /* Do we need any barrier here or is __sync_add_and_fetch acting
> - as the needed LoadLoad barrier already? */
> - ret += __sync_add_and_fetch (&bar->awaited, -1) == 0;
> + unsigned int ret = __atomic_load_4 (&bar->generation, MEMMODEL_ACQUIRE) & ~3;
> + ret += __atomic_add_fetch (&bar->awaited, -1, MEMMODEL_ACQ_REL) == 0;
Given that the read from bar->generation is ACQ, we don't need a duplicate
barrier from the REL on the atomic add. I believe both can be MEMMODEL_ACQUIRE
both in order to force the ordering of these two memops, as well as force these
to happen before anything subsequent.
The s/_4/_n/ change needs doing.
Otherwise ok.
r~