Re: pg_stat_activity crashes

On Thu, Apr 21, 2016 at 9:47 PM, Kyotaro HORIGUCHI
<horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> A lock was already held in BackendPidGetProc(). Is it also
> needless? If so, we should use BackendPidGetProcWithLock() instad
> (the name seems a bit confusing, though).

Oh, that's really sad. No, that lock is definitely needed. We should
probably try to figure out some day if there is a way to make this
completely lockless, but that'll have to be 9.7 material or later.
:-(

> What I did in the patch was just extending the lock duration
> until reading the pointer proc. I didn't added any additional
> lock.

Sorry, I didn't realize that. Good point.

>> > The
>> > only thing we need to do is to prevent the value from being read
>> > twice, and we already have precedent for how to prevent that in
>> > freelist.c.
>
> However, I don't have objections for the patch applied.

OK, let's leave it like that for now, then.

--
Robert Haas
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