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

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(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.
This commit is contained in:
Tom Lane
2002-09-16 01:24:41 +00:00
parent 5ea9322872
commit 53e95eee84
2 changed files with 10 additions and 3 deletions
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6
src/backend/commands/async.c
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* IDENTIFICATION * 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. * ever turned on.
*/ */
/* Don't joggle the elbow of proc_exit */
if (proc_exit_inprogress)
return;
if (notifyInterruptEnabled) if (notifyInterruptEnabled)
{ {
/* /*

7
src/backend/tcop/postgres.c
View File

@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * 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 * NOTES
* this is the "main" module of the postgres backend and * this is the "main" module of the postgres backend and
@ -1071,12 +1071,14 @@ ProcessInterrupts(void)
ProcDiePending = false; ProcDiePending = false;
QueryCancelPending = false; /* ProcDie trumps QueryCancel */ QueryCancelPending = false; /* ProcDie trumps QueryCancel */
ImmediateInterruptOK = false; /* not idle anymore */ ImmediateInterruptOK = false; /* not idle anymore */
DisableNotifyInterrupt();
elog(FATAL, "This connection has been terminated by the administrator."); elog(FATAL, "This connection has been terminated by the administrator.");
} }
if (QueryCancelPending) if (QueryCancelPending)
{ {
QueryCancelPending = false; QueryCancelPending = false;
ImmediateInterruptOK = false; /* not idle anymore */ ImmediateInterruptOK = false; /* not idle anymore */
DisableNotifyInterrupt();
elog(ERROR, "Query was cancelled."); elog(ERROR, "Query was cancelled.");
} }
/* If we get here, do nothing (probably, QueryCancelPending was reset) */ /* If we get here, do nothing (probably, QueryCancelPending was reset) */
@ -1689,7 +1691,7 @@ PostgresMain(int argc, char *argv[], const char *username)
if (!IsUnderPostmaster) if (!IsUnderPostmaster)
{ {
puts("\nPOSTGRES backend interactive interface "); 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; QueryCancelPending = false;
InterruptHoldoffCount = 1; InterruptHoldoffCount = 1;
CritSectionCount = 0; /* should be unnecessary, but... */ CritSectionCount = 0; /* should be unnecessary, but... */
DisableNotifyInterrupt();
debug_query_string = NULL; debug_query_string = NULL;
/* /*