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Remove set_latch_on_sigusr1 flag.

Browse Source 
This flag has proven to be a recipe for bugs, and it doesn't seem like
it can really buy anything in terms of performance.  So let's just
*always* set the process latch when we receive SIGUSR1 instead of
trying to do it only when needed.

Per my recent proposal on pgsql-hackers.
This commit is contained in:
Robert Haas
2015-10-09 14:31:04 -04:00
parent b7aac36245
commit db0f6cad48
6 changed files with 91 additions and 158 deletions
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78
src/backend/storage/ipc/shm_mq.c
View File

@@ -962,63 +962,49 @@ static bool
shm_mq_wait_internal(volatile shm_mq *mq, PGPROC *volatile * ptr,
BackgroundWorkerHandle *handle)
{
bool save_set_latch_on_sigusr1;
bool result = false;
save_set_latch_on_sigusr1 = set_latch_on_sigusr1;
if (handle != NULL)
set_latch_on_sigusr1 = true;
PG_TRY();
for (;;)
{
for (;;)
BgwHandleStatus status;
pid_t pid;
bool detached;
/* Acquire the lock just long enough to check the pointer. */
SpinLockAcquire(&mq->mq_mutex);
detached = mq->mq_detached;
result = (*ptr != NULL);
SpinLockRelease(&mq->mq_mutex);
/* Fail if detached; else succeed if initialized. */
if (detached)
{
BgwHandleStatus status;
pid_t pid;
bool detached;
result = false;
break;
}
if (result)
break;
/* Acquire the lock just long enough to check the pointer. */
SpinLockAcquire(&mq->mq_mutex);
detached = mq->mq_detached;
result = (*ptr != NULL);
SpinLockRelease(&mq->mq_mutex);
/* Fail if detached; else succeed if initialized. */
if (detached)
if (handle != NULL)
{
/* Check for unexpected worker death. */
status = GetBackgroundWorkerPid(handle, &pid);
if (status != BGWH_STARTED && status != BGWH_NOT_YET_STARTED)
{
result = false;
break;
}
if (result)
break;
if (handle != NULL)
{
/* Check for unexpected worker death. */
status = GetBackgroundWorkerPid(handle, &pid);
if (status != BGWH_STARTED && status != BGWH_NOT_YET_STARTED)
{
result = false;
break;
}
}
/* Wait to be signalled. */
WaitLatch(MyLatch, WL_LATCH_SET, 0);
/* An interrupt may have occurred while we were waiting. */
CHECK_FOR_INTERRUPTS();
/* Reset the latch so we don't spin. */
ResetLatch(MyLatch);
}
/* Wait to be signalled. */
WaitLatch(MyLatch, WL_LATCH_SET, 0);
/* An interrupt may have occurred while we were waiting. */
CHECK_FOR_INTERRUPTS();
/* Reset the latch so we don't spin. */
ResetLatch(MyLatch);
}
PG_CATCH();
{
set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
PG_RE_THROW();
}
PG_END_TRY();
return result;
}