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| author | Thomas Munro <tmunro@postgresql.org> | 2019-07-13 13:55:10 +1200 |
|---|---|---|
| committer | Thomas Munro <tmunro@postgresql.org> | 2019-07-13 14:50:18 +1200 |
| commit | b91dd9de5ea0839d0d248ebbe8cb926c3df52c7c (patch) | |
| tree | 19da475a11d2fae877149ea88a686b334e012f29 /src/backend/storage/lmgr/condition_variable.c | |
| parent | 1321509fa43293615c4e5fa5dc8eed5286f479b1 (diff) | |
| download | postgresql-b91dd9de5ea0839d0d248ebbe8cb926c3df52c7c.tar.gz postgresql-b91dd9de5ea0839d0d248ebbe8cb926c3df52c7c.zip | |
Forward received condition variable signals on cancel.
After a process decides not to wait for a condition variable, it can
still consume a signal before it reaches ConditionVariableCancelSleep().
In that case, pass the signal on to another waiter if possible, so that
a signal doesn't go missing when there is another process ready to
receive it.
Author: Thomas Munro
Reviewed-by: Shawn Debnath
Discussion: https://postgr.es/m/CA%2BhUKGLQ_RW%2BXs8znDn36e-%2Bmq2--zrPemBqTQ8eKT-VO1OF4Q%40mail.gmail.com
Diffstat (limited to 'src/backend/storage/lmgr/condition_variable.c')
| -rw-r--r-- | src/backend/storage/lmgr/condition_variable.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/src/backend/storage/lmgr/condition_variable.c b/src/backend/storage/lmgr/condition_variable.c index bc8607efe45..e08507f0cc5 100644 --- a/src/backend/storage/lmgr/condition_variable.c +++ b/src/backend/storage/lmgr/condition_variable.c @@ -245,6 +245,7 @@ void ConditionVariableCancelSleep(void) { ConditionVariable *cv = cv_sleep_target; + bool signaled = false; if (cv == NULL) return; @@ -252,8 +253,18 @@ ConditionVariableCancelSleep(void) SpinLockAcquire(&cv->mutex); if (proclist_contains(&cv->wakeup, MyProc->pgprocno, cvWaitLink)) proclist_delete(&cv->wakeup, MyProc->pgprocno, cvWaitLink); + else + signaled = true; SpinLockRelease(&cv->mutex); + /* + * If we've received a signal, pass it on to another waiting process, if + * there is one. Otherwise a call to ConditionVariableSignal() might get + * lost, despite there being another process ready to handle it. + */ + if (signaled) + ConditionVariableSignal(cv); + cv_sleep_target = NULL; } |