diff options
| -rw-r--r-- | src/backend/storage/lmgr/condition_variable.c | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/src/backend/storage/lmgr/condition_variable.c b/src/backend/storage/lmgr/condition_variable.c index 552bdaaf809..730adf1c57f 100644 --- a/src/backend/storage/lmgr/condition_variable.c +++ b/src/backend/storage/lmgr/condition_variable.c @@ -70,10 +70,15 @@ ConditionVariablePrepareToSleep(ConditionVariable *cv) } /* - * It's not legal to prepare a sleep until the previous sleep has been - * completed or canceled. + * If some other sleep is already prepared, cancel it; this is necessary + * because we have just one static variable tracking the prepared sleep, + * and also only one cvWaitLink in our PGPROC. It's okay to do this + * because whenever control does return to the other test-and-sleep loop, + * its ConditionVariableSleep call will just re-establish that sleep as + * the prepared one. */ - Assert(cv_sleep_target == NULL); + if (cv_sleep_target != NULL) + ConditionVariableCancelSleep(); /* Record the condition variable on which we will sleep. */ cv_sleep_target = cv; @@ -121,16 +126,16 @@ ConditionVariableSleep(ConditionVariable *cv, uint32 wait_event_info) * allows you to skip manipulation of the wait list, or not met initially, * in which case preparing first allows you to skip a spurious test of the * caller's exit condition. + * + * If we are currently prepared to sleep on some other CV, we just cancel + * that and prepare this one; see ConditionVariablePrepareToSleep. */ - if (cv_sleep_target == NULL) + if (cv_sleep_target != cv) { ConditionVariablePrepareToSleep(cv); return; } - /* Any earlier condition variable sleep must have been canceled. */ - Assert(cv_sleep_target == cv); - while (!done) { CHECK_FOR_INTERRUPTS(); @@ -246,7 +251,8 @@ ConditionVariableBroadcast(ConditionVariable *cv) * prepared CV sleep. The next call to ConditionVariableSleep will take * care of re-establishing the lost state. */ - ConditionVariableCancelSleep(); + if (cv_sleep_target != NULL) + ConditionVariableCancelSleep(); /* * Inspect the state of the queue. If it's empty, we have nothing to do. |