From 78aaa0e82335527b8cc91601c98c9abbbc3ef3ee Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Tue, 28 Jan 2020 15:28:36 +1300 Subject: [PATCH] Don't reset latch in ConditionVariablePrepareToSleep(). It's not OK to do that without calling CHECK_FOR_INTERRUPTS(). Let the next wait loop deal with it, following the usual pattern. One consequence of this bug was that a SIGTERM delivered in a very narrow timing window could leave a parallel worker process waiting forever for a condition variable that will never be signaled, after an error was raised in other process. The code is a bit different in the stable branches due to commit 1321509f, making problems less likely there. No back-patch for now, but we may finish up deciding to make a similar change after more discussion. Author: Thomas Munro Reviewed-by: Shawn Debnath Reported-by: Tomas Vondra Discussion: https://postgr.es/m/CA%2BhUKGJOm8zZHjVA8svoNT3tHY0XdqmaC_kHitmgXDQM49m1dA%40mail.gmail.com --- src/backend/storage/lmgr/condition_variable.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/src/backend/storage/lmgr/condition_variable.c b/src/backend/storage/lmgr/condition_variable.c index 0e7f07961ee..37b6a4eecdb 100644 --- a/src/backend/storage/lmgr/condition_variable.c +++ b/src/backend/storage/lmgr/condition_variable.c @@ -93,12 +93,6 @@ ConditionVariablePrepareToSleep(ConditionVariable *cv) /* Record the condition variable on which we will sleep. */ cv_sleep_target = cv; - /* - * Reset my latch before adding myself to the queue, to ensure that we - * don't miss a wakeup that occurs immediately. - */ - ResetLatch(MyLatch); - /* Add myself to the wait queue. */ SpinLockAcquire(&cv->mutex); proclist_push_tail(&cv->wakeup, pgprocno, cvWaitLink);