From 44445b28d265fe91fea3da47bd3a8c4007ce87e5 Mon Sep 17 00:00:00 2001 From: Andres Freund <andres@anarazel.de> Date: Tue, 3 Jun 2014 14:02:54 +0200 Subject: [PATCH] Set the process latch when processing recovery conflict interrupts. Because RecoveryConflictInterrupt() didn't set the process latch anything using the latter to wait for events didn't get notified about recovery conflicts. Most latch users are never the target of recovery conflicts, which explains the lack of reports about this until now. Since 9.3 two possible affected users exist though: The sql callable pg_sleep() now uses latches to wait and background workers are expected to use latches in their main loop. Both would currently wait until the end of WaitLatch's timeout. Fix by adding a SetLatch() to RecoveryConflictInterrupt(). It'd also be possible to fix the issue by having each latch user set set_latch_on_sigusr1. That seems failure prone and though, as most of these callsites won't often receive recovery conflicts and thus will likely only be tested against normal query cancels et al. It'd also be unnecessarily verbose. Backpatch to 9.1 where latches were introduced. Arguably 9.3 would be sufficient, because that's where pg_sleep() was converted to waiting on the latch and background workers got introduced; but there could be user level code making use of the latch pre 9.3. --- src/backend/tcop/postgres.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c index 89d2d4a7b8a..9abc11bea51 100644 --- a/src/backend/tcop/postgres.c +++ b/src/backend/tcop/postgres.c @@ -2806,6 +2806,16 @@ RecoveryConflictInterrupt(ProcSignalReason reason) } } + /* + * Set the process latch. This function essentially emulates signal + * handlers like die() and StatementCancelHandler() and it seems prudent + * to behave similarly as they do. Alternatively all plain backend code + * waiting on that latch, expecting to get interrupted by query cancels et + * al., would also need to set set_latch_on_sigusr1. + */ + if (MyProc) + SetLatch(&MyProc->procLatch); + errno = save_errno; } -- GitLab