Fix for rare race-condition-like failure: if a backend receives SIGUSR2

tglsfdc · tglsfdc · commit 53e95eee84e0 · 2002-09-16T01:24:41.000Z
(notify/SI-overrun interrupt) while it is in process of doing proc_exit,
it is possible for Async_NotifyHandler() to try to start a transaction
when one is already running.  This leads to Asserts() or worse.  I think
it may only be possible to occur when frontend synchronization is lost
(ie, the elog(FATAL) in SocketBackend() fires), but that is a standard
occurrence after error during COPY.  In any case, I have seen this
failure occur during regression tests, so it is definitely possible.
diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.90 2002/09/02 02:47:01 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.91 2002/09/16 01:24:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -593,6 +593,10 @@ Async_NotifyHandler(SIGNAL_ARGS)
 	 * ever turned on.
 	 */
 
+	/* Don't joggle the elbow of proc_exit */
+	if (proc_exit_inprogress)
+		return;
+
 	if (notifyInterruptEnabled)
 	{
 		/*
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.291 2002/09/04 20:31:26 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.292 2002/09/16 01:24:41 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -1071,12 +1071,14 @@ ProcessInterrupts(void)
 		ProcDiePending = false;
 		QueryCancelPending = false;		/* ProcDie trumps QueryCancel */
 		ImmediateInterruptOK = false;	/* not idle anymore */
+		DisableNotifyInterrupt();
 		elog(FATAL, "This connection has been terminated by the administrator.");
 	}
 	if (QueryCancelPending)
 	{
 		QueryCancelPending = false;
 		ImmediateInterruptOK = false;	/* not idle anymore */
+		DisableNotifyInterrupt();
 		elog(ERROR, "Query was cancelled.");
 	}
 	/* If we get here, do nothing (probably, QueryCancelPending was reset) */
@@ -1689,7 +1691,7 @@ PostgresMain(int argc, char *argv[], const char *username)
 	if (!IsUnderPostmaster)
 	{
 		puts("\nPOSTGRES backend interactive interface ");
-		puts("$Revision: 1.291 $ $Date: 2002/09/04 20:31:26 $\n");
+		puts("$Revision: 1.292 $ $Date: 2002/09/16 01:24:41 $\n");
 	}
 
 	/*
@@ -1736,6 +1738,7 @@ PostgresMain(int argc, char *argv[], const char *username)
 		QueryCancelPending = false;
 		InterruptHoldoffCount = 1;
 		CritSectionCount = 0;	/* should be unnecessary, but... */
+		DisableNotifyInterrupt();
 		debug_query_string = NULL;
 
 		/*

Original file line number	Diff line number	Diff line change
`@@ -7,7 +7,7 @@`
`7`	`7`	`* Portions Copyright (c) 1994, Regents of the University of California`
`8`	`8`	`*`
`9`	`9`	`* IDENTIFICATION`
`10`		`- * $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.90 2002/09/02 02:47:01 momjian Exp $`
	`10`	`+ * $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.91 2002/09/16 01:24:41 tgl Exp $`
`11`	`11`	`*`
`12`	`12`	`*-------------------------------------------------------------------------`
`13`	`13`	`*/`
`@@ -593,6 +593,10 @@ Async_NotifyHandler(SIGNAL_ARGS)`
`593`	`593`	`* ever turned on.`
`594`	`594`	`*/`
`595`	`595`
	`596`	`+ /* Don't joggle the elbow of proc_exit */`
	`597`	`+ if (proc_exit_inprogress)`
	`598`	`+ return;`
	`599`	`+`
`596`	`600`	`if (notifyInterruptEnabled)`
`597`	`601`	`{`
`598`	`602`	`/*`
Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@`
`8`	`8`	`*`
`9`	`9`	`*`
`10`	`10`	`* IDENTIFICATION`
`11`		`- * $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.291 2002/09/04 20:31:26 momjian Exp $`
	`11`	`+ * $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.292 2002/09/16 01:24:41 tgl Exp $`
`12`	`12`	`*`
`13`	`13`	`* NOTES`
`14`	`14`	`* this is the "main" module of the postgres backend and`
`@@ -1071,12 +1071,14 @@ ProcessInterrupts(void)`
`1071`	`1071`	`ProcDiePending = false;`
`1072`	`1072`	`QueryCancelPending = false; /* ProcDie trumps QueryCancel */`
`1073`	`1073`	`ImmediateInterruptOK = false; /* not idle anymore */`
	`1074`	`+ DisableNotifyInterrupt();`
`1074`	`1075`	`elog(FATAL, "This connection has been terminated by the administrator.");`
`1075`	`1076`	`}`
`1076`	`1077`	`if (QueryCancelPending)`
`1077`	`1078`	`{`
`1078`	`1079`	`QueryCancelPending = false;`
`1079`	`1080`	`ImmediateInterruptOK = false; /* not idle anymore */`
	`1081`	`+ DisableNotifyInterrupt();`
`1080`	`1082`	`elog(ERROR, "Query was cancelled.");`
`1081`	`1083`	`}`
`1082`	`1084`	`/* If we get here, do nothing (probably, QueryCancelPending was reset) */`
`@@ -1689,7 +1691,7 @@ PostgresMain(int argc, char argv[], const char username)`
`1689`	`1691`	`if (!IsUnderPostmaster)`
`1690`	`1692`	`{`
`1691`	`1693`	`puts("\nPOSTGRES backend interactive interface ");`
`1692`		`- puts("$Revision: 1.291 $ $Date: 2002/09/04 20:31:26 $\n");`
	`1694`	`+ puts("$Revision: 1.292 $ $Date: 2002/09/16 01:24:41 $\n");`
`1693`	`1695`	`}`
`1694`	`1696`
`1695`	`1697`	`/*`
`@@ -1736,6 +1738,7 @@ PostgresMain(int argc, char argv[], const char username)`
`1736`	`1738`	`QueryCancelPending = false;`
`1737`	`1739`	`InterruptHoldoffCount = 1;`
`1738`	`1740`	`CritSectionCount = 0; /* should be unnecessary, but... */`
	`1741`	`+ DisableNotifyInterrupt();`
`1739`	`1742`	`debug_query_string = NULL;`
`1740`	`1743`
`1741`	`1744`	`/*`