On Thu, May 18, 2017 at 1:43 PM, Thomas Munro <thomas.mu...@enterprisedb.com> wrote: > On Thu, May 11, 2017 at 1:48 PM, Michael Paquier > <michael.paqu...@gmail.com> wrote: >> I had my eyes on the WAL sender code this morning, and I have noticed >> that walsender.c is not completely consistent with the PID lookups it >> does in walsender.c. In two code paths, the PID value is checked >> without holding the WAL sender spin lock (WalSndRqstFileReload and >> pg_stat_get_wal_senders), which looks like a very bad idea contrary to >> what the new WalSndWaitStopping() does and what InitWalSenderSlot() is >> doing for ages. > > There is also code that accesses shared walsender state without > spinlocks over in syncrep.c. I think that file could use a few words > of explanation for why it's OK to access pid, state and flush without > synchronisation.
Yes, that is read during the quorum and priority sync evaluation. Except sync_standby_priority, all the other variables should be protected using the spin lock of the WAL sender. walsender_private.h is clear regarding that. So the current coding is inconsistent even there. Attached is an updated patch. -- Michael
walsnd-pid-races-v2.patch
Description: Binary data
-- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
