Fix recent breakage of query-cancel logic, see my pghackers message

of 6 Jan 2001 21:55.

1 files changed, 53 insertions, 21 deletions

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index a8b7b4ec1bc..a73ba4df4ab 100644
--- 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 1.198 2000/12/20 21:51:52 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.199 2001/01/07 04:17:29 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -94,7 +94,7 @@ DLLIMPORT sigjmp_buf Warn_restart;
 
 bool		Warn_restart_ready = false;
 bool		InError = false;
-bool		ProcDiePending = false;
+volatile bool ProcDiePending = false;
 
 static bool EchoQuery = false;	/* default don't echo */
 char		pg_pathname[MAXPGPATH];
@@ -920,7 +920,10 @@ finish_xact_command(void)
 void
 handle_warn(SIGNAL_ARGS)
 {
-	/* Don't joggle the elbow of a critical section */
+	/* Don't joggle the elbow of proc_exit */
+	if (proc_exit_inprogress)
+		return;
+	/* Don't joggle the elbow of a critical section, either */
 	if (CritSectionCount > 0)
 	{
 		QueryCancel = true;
@@ -956,28 +959,38 @@ quickdie(SIGNAL_ARGS)
 void
 die(SIGNAL_ARGS)
 {
+	int			save_errno = errno;
+
 	PG_SETMASK(&BlockSig);
 
-	/* Don't joggle the elbow of a critical section */
+	/* Don't joggle the elbow of proc_exit */
+	if (proc_exit_inprogress)
+	{
+		errno = save_errno;
+		return;
+	}
+	/* Don't joggle the elbow of a critical section, either */
 	if (CritSectionCount > 0)
 	{
-		QueryCancel = true;
 		ProcDiePending = true;
+		errno = save_errno;
 		return;
 	}
-	/* Don't joggle the elbow of proc_exit, either */
-	if (proc_exit_inprogress)
-		return;
-	elog(FATAL, "The system is shutting down");
+	/* Otherwise force immediate proc_exit */
+	ForceProcDie();
 }
 
-/* signal handler for floating point exception */
-static void
-FloatExceptionHandler(SIGNAL_ARGS)
+/*
+ * This is split out of die() so that it can be invoked later from
+ * END_CRIT_CODE.
+ */
+void
+ForceProcDie(void)
 {
-	elog(ERROR, "floating point exception!"
-		 " The last floating point operation either exceeded legal ranges"
-		 " or was a divide by zero");
+	/* Reset flag to avoid another elog() during shutdown */
+	ProcDiePending = false;
+	/* Send error message and do proc_exit() */
+	elog(FATAL, "The system is shutting down");
 }
 
 /* signal handler for query cancel signal from postmaster */
@@ -986,22 +999,41 @@ QueryCancelHandler(SIGNAL_ARGS)
 {
 	int			save_errno = errno;
 
+	/* Don't joggle the elbow of proc_exit, nor an already-in-progress abort */
+	if (proc_exit_inprogress || InError)
+	{
+		errno = save_errno;
+		return;
+	}
+
+	/* Set flag to cause CancelQuery to be called when it's safe */
 	QueryCancel = true;
+
+	/* If we happen to be waiting for a lock, get out of that */
 	LockWaitCancel();
+
+	/* Otherwise, bide our time... */
 	errno = save_errno;
 }
 
 void
 CancelQuery(void)
 {
-
-	/*
-	 * QueryCancel flag will be reset in main loop, which we reach by
-	 * longjmp from elog().
-	 */
+	/* Reset flag to avoid another elog() during error recovery */
+	QueryCancel = false;
+	/* Create an artificial error condition to get out of query */
 	elog(ERROR, "Query was cancelled.");
 }
 
+/* signal handler for floating point exception */
+static void
+FloatExceptionHandler(SIGNAL_ARGS)
+{
+	elog(ERROR, "floating point exception!"
+		 " The last floating point operation either exceeded legal ranges"
+		 " or was a divide by zero");
+}
+
 static void
 SigHupHandler(SIGNAL_ARGS)
 {
@@ -1651,7 +1683,7 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[], const cha
 	if (!IsUnderPostmaster)
 	{
 		puts("\nPOSTGRES backend interactive interface ");
-		puts("$Revision: 1.198 $ $Date: 2000/12/20 21:51:52 $\n");
+		puts("$Revision: 1.199 $ $Date: 2001/01/07 04:17:29 $\n");
 	}
 
 	/*