Re: BUG #13985: Segmentation fault on PREPARE TRANSACTION

On Thu, Feb 25, 2016 at 3:51 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "Shulgin, Oleksandr" <oleksandr(dot)shulgin(at)zalando(dot)de> writes:
> > On Wed, Feb 24, 2016 at 10:52 PM, Andres Freund <andres(at)anarazel(dot)de>
> wrote:
> > At the very least ISTM that we have to make pgprocno volatile (or use a
> >> memory barrier - but we don't have sufficient support for those in the
> >> older branches), and move the PGPROC/PGXACT lookups after the == -1
> >> check.
>
> > Use of volatile doesn't change the resulting code dramatically for me.
>
> Marking pgprocno volatile is silly. What *is* missing is this:
>
> - ProcArrayStruct *arrayP = procArray;
> + volatile ProcArrayStruct *arrayP = procArray;
>
> which corresponds directly to what the problem is: the storage arrayP
> is pointing at may change asynchronously.
>

Right, this makes a lot more sense.

--
Alex