Use WaitLatch() for condition variables.
Previously, condition_variable.c created a long lived WaitEventSet to
avoid extra system calls.  WaitLatch() now uses something similar
internally, so there is no point in wasting an extra kernel descriptor.
Discussion:
/* Initially, we are not prepared to sleep on any condition variable. */
static ConditionVariable *cv_sleep_target = NULL;
-/* Reusable WaitEventSet. */
-static WaitEventSet *cv_wait_event_set = NULL;
-
/*
* Initialize a condition variable.
*/
@@ -62,23 +59,6 @@ ConditionVariablePrepareToSleep(ConditionVariable *cv)
{
int pgprocno = MyProc->pgprocno;
- /*
- * If first time through in this process, create a WaitEventSet, which
- * we'll reuse for all condition variable sleeps.
- */
- if (cv_wait_event_set == NULL)
- {
- WaitEventSet *new_event_set;
-
- new_event_set = CreateWaitEventSet(TopMemoryContext, 2);
- AddWaitEventToSet(new_event_set, WL_LATCH_SET, PGINVALID_SOCKET,
- MyLatch, NULL);
- AddWaitEventToSet(new_event_set, WL_EXIT_ON_PM_DEATH, PGINVALID_SOCKET,
- NULL, NULL);
- /* Don't set cv_wait_event_set until we have a correct WES. */
- cv_wait_event_set = new_event_set;
- }
-
/*
* If some other sleep is already prepared, cancel it; this is necessary
* because we have just one static variable tracking the prepared sleep,
@@ -135,6 +115,7 @@ ConditionVariableTimedSleep(ConditionVariable *cv, long timeout,
long cur_timeout = -1;
instr_time start_time;
instr_time cur_time;
+ int wait_events;
/*
* If the caller didn't prepare to sleep explicitly, then do so now and
@@ -166,19 +147,20 @@ ConditionVariableTimedSleep(ConditionVariable *cv, long timeout,
INSTR_TIME_SET_CURRENT(start_time);
Assert(timeout >= 0 && timeout <= INT_MAX);
cur_timeout = timeout;
+ wait_events = WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH;
}
+ else
+ wait_events = WL_LATCH_SET | WL_EXIT_ON_PM_DEATH;
while (true)
{
- WaitEvent event;
bool done = false;
/*
* Wait for latch to be set. (If we're awakened for some other
* reason, the code below will cope anyway.)
*/
- (void) WaitEventSetWait(cv_wait_event_set, cur_timeout, &event, 1,
- wait_event_info);
+ (void) WaitLatch(MyLatch, wait_events, cur_timeout, wait_event_info);
/* Reset latch before examining the state of the wait list. */
ResetLatch(MyLatch);
