postgrespro.git / summary / log / commit / refs

commit    78aaa0e82335527b8cc91601c98c9abbbc3ef3ee
Author:   Thomas Munro <tmunro@postgresql.org>
Date:     Tue Jan 28 02:28:36 2020 +0000

    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 0e7f07961e..37b6a4eecd 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);


[parent: 05f18c6b6b6e]