Hi.
Recent commit 555276f8594087ba15e0d58e38cd2186b9f39f6d introduced final
cleanup of node->as_eventset in ExecAppendAsyncEventWait().
Unfortunately, now this function can return in the middle of TRY/FINALLY
block, without restoring PG_exception_stack.
We found this while working on our FDW. Unfortunately, I couldn't
reproduce the issue with postgres_fdw, but it seems it is also affected.
The following patch heals the issue.
-- l
Best regards,
Alexander Pyhalov,
Postgres Professional
From 025f40894d6d8f499144f0f7c45c0a124a46c408 Mon Sep 17 00:00:00 2001
From: Alexander Pyhalov <a.pyha...@postgrespro.ru>
Date: Fri, 23 Feb 2024 13:06:40 +0300
Subject: [PATCH] Avoid corrupting PG_exception_stack in
ExecAppendAsyncEventWait()
After commit 555276f8594087ba15e0d58e38cd2186b9f39f6d
ExecAppendAsyncEventWait() could corrupt PG_exception_stack
after returning in the the middle of PG_TRY()/PG_END_TRY() block.
It should exit only after PG_END_TRY().
---
src/backend/executor/nodeAppend.c | 27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)
diff --git a/src/backend/executor/nodeAppend.c b/src/backend/executor/nodeAppend.c
index baba3ceea23..42962e80177 100644
--- a/src/backend/executor/nodeAppend.c
+++ b/src/backend/executor/nodeAppend.c
@@ -1052,21 +1052,22 @@ ExecAppendAsyncEventWait(AppendState *node)
*/
if (GetNumRegisteredWaitEvents(node->as_eventset) == 1)
{
- FreeWaitEventSet(node->as_eventset);
- node->as_eventset = NULL;
- return;
+ /* Return after PG_TRY()/PG_END_TRY() block */
+ noccurred = 0;
}
+ else
+ {
+ /* Return at most EVENT_BUFFER_SIZE events in one call. */
+ if (nevents > EVENT_BUFFER_SIZE)
+ nevents = EVENT_BUFFER_SIZE;
- /* Return at most EVENT_BUFFER_SIZE events in one call. */
- if (nevents > EVENT_BUFFER_SIZE)
- nevents = EVENT_BUFFER_SIZE;
-
- /*
- * If the timeout is -1, wait until at least one event occurs. If the
- * timeout is 0, poll for events, but do not wait at all.
- */
- noccurred = WaitEventSetWait(node->as_eventset, timeout, occurred_event,
- nevents, WAIT_EVENT_APPEND_READY);
+ /*
+ * If the timeout is -1, wait until at least one event occurs. If
+ * the timeout is 0, poll for events, but do not wait at all.
+ */
+ noccurred = WaitEventSetWait(node->as_eventset, timeout, occurred_event,
+ nevents, WAIT_EVENT_APPEND_READY);
+ }
}
PG_FINALLY();
{
--
2.34.1
