On Wed, Oct 2, 2013 at 9:45 AM, Ants Aasma <a...@cybertec.at> wrote: > I haven't reviewed the code in as much detail to say if there is an > actual race here, I tend to think there's probably not, but the > specific pattern that I had in mind is that with the following actual > code:
hm. I think there *is* a race. 2+ threads could race to the line: LocalRecoveryInProgress = xlogctl->SharedRecoveryInProgress; and simultaneously set the value of LocalRecoveryInProgress to false, and both engage InitXLOGAccess, which is destructive. The move operation is atomic, but I don't think there's any guarantee the reads to xlogctl->SharedRecoveryInProgress are ordered between threads without a lock. I don't think the memory barrier will fix this. Do you agree? If so, my earlier patch (recovery4) is another take on this problem, and arguable safer; the unlocked read is in a separate path that does not engage InitXLOGAccess() merlin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
