From 6322e84430e2b1756fbf31072679507266f2b304 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 26 Jan 2008 19:55:08 +0000
Subject: Change StatementCancelHandler() to check the DoingCommandRead flag to
 decide whether to execute an immediate interrupt, rather than testing whether
 LockWaitCancel() cancelled a lock wait.  The old way misclassified the case
 where we were blocked in ProcWaitForSignal(), and arguably would misclassify
 any other future additions of new ImmediateInterruptOK states too.  This
 allows reverting the old kluge that gave LockWaitCancel() a return value,
 since no callers care anymore.  Improve comments in the various
 implementations of PGSemaphoreLock() to explain that on some platforms, the
 assumption that semop() exits after a signal is wrong, and so we must ensure
 that the signal handler itself throws elog if we want cancel or die
 interrupts to be effective.  Per testing related to bug #3883, though this
 patch doesn't solve those problems fully.

Perhaps this change should be back-patched, but since pre-8.3 branches aren't
really relying on autovacuum to respond to SIGINT, it doesn't seem critical
for them.
---
 src/backend/tcop/postgres.c | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

(limited to 'src/backend/tcop/postgres.c')

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 05127c40b30..325411df09c 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.541 2008/01/01 19:45:52 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.542 2008/01/26 19:55:08 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -2449,10 +2449,9 @@ die(SIGNAL_ARGS)
 			/* bump holdoff count to make ProcessInterrupts() a no-op */
 			/* until we are done getting ready for it */
 			InterruptHoldoffCount++;
+			LockWaitCancel();	/* prevent CheckDeadLock from running */
 			DisableNotifyInterrupt();
 			DisableCatchupInterrupt();
-			/* Make sure CheckDeadLock won't run while shutting down... */
-			LockWaitCancel();
 			InterruptHoldoffCount--;
 			ProcessInterrupts();
 		}
@@ -2498,20 +2497,16 @@ StatementCancelHandler(SIGNAL_ARGS)
 		 * waiting for input, however.
 		 */
 		if (ImmediateInterruptOK && InterruptHoldoffCount == 0 &&
-			CritSectionCount == 0)
+			CritSectionCount == 0 && !DoingCommandRead)
 		{
 			/* bump holdoff count to make ProcessInterrupts() a no-op */
 			/* until we are done getting ready for it */
 			InterruptHoldoffCount++;
-			if (LockWaitCancel())
-			{
-				DisableNotifyInterrupt();
-				DisableCatchupInterrupt();
-				InterruptHoldoffCount--;
-				ProcessInterrupts();
-			}
-			else
-				InterruptHoldoffCount--;
+			LockWaitCancel();	/* prevent CheckDeadLock from running */
+			DisableNotifyInterrupt();
+			DisableCatchupInterrupt();
+			InterruptHoldoffCount--;
+			ProcessInterrupts();
 		}
 	}
 
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