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Don't return in PG_TRY() block when cancellations happen in WaitForConnections(). (#1923) 

We shouldn't return in middle of a PG_TRY() block because if we do, we won't reset PG_exception_stack, and later when a re-throw tries to jump to the jump-point which was active in this PG_TRY() block, it seg-faults.

We used to return in middle of PG_TRY() block in WaitForConnections() where we checked for cancellations. Whenever cancellations were caught here, Citus crashed. And example was reported by @onderkalaci at #1903.
pull/1928/head
Hadi Moshayedi 2018-01-03 09:54:03 -05:00 committed by GitHub
parent 8f69973411
commit 5d7c52ffa6
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 13 additions and 3 deletions
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16
src/backend/distributed/connection/remote_commands.c
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@ -781,6 +781,7 @@ WaitForAllConnections(List *connectionList, bool raiseInterrupts)
while (pendingConnectionsStartIndex < totalConnectionCount) while (pendingConnectionsStartIndex < totalConnectionCount)
{ {
bool cancellationReceived = false;
int eventIndex = 0; int eventIndex = 0;
int eventCount = 0; int eventCount = 0;
long timeout = -1; long timeout = -1;
@ -837,9 +838,13 @@ WaitForAllConnections(List *connectionList, bool raiseInterrupts)
if (InterruptHoldoffCount > 0 && (QueryCancelPending || if (InterruptHoldoffCount > 0 && (QueryCancelPending ||
ProcDiePending)) ProcDiePending))
{ {
/* return immediately in case of cancellation */ /*
FreeWaitEventSet(waitEventSet); * Break out of event loop immediately in case of cancellation.
return; * We cannot use "return" here inside a PG_TRY() block since
* then the exception stack won't be reset.
*/
cancellationReceived = true;
break;
} }
continue; continue;
@ -905,6 +910,11 @@ WaitForAllConnections(List *connectionList, bool raiseInterrupts)
} }
} }
if (cancellationReceived)
{
break;
}
/* move non-ready connections to the back of the array */ /* move non-ready connections to the back of the array */
for (connectionIndex = pendingConnectionsStartIndex; for (connectionIndex = pendingConnectionsStartIndex;
connectionIndex < totalConnectionCount; connectionIndex++) connectionIndex < totalConnectionCount; connectionIndex++)