Substantial rewrite of async.c to avoid problems with non-reentrant stdio

and possibly other problems.  Minor changes in xact.c and postgres.c's
main loop to support new handling of async NOTIFY.

src/backend/access/transam/xact.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.23 1998/09/01 04:27:19 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.24 1998/10/06 02:39:58 tgl Exp $
  *
  * NOTES
  *		Transaction aborts can now occur two ways:
@@ -901,6 +901,9 @@ CommitTransaction()
 	/* handle commit for large objects [ PA, 7/17/98 ] */
 	_lo_commit();
 
+	/* NOTIFY commit must also come before lower-level cleanup */
+	AtCommit_Notify();
+
 	CloseSequences();
 	DestroyTempRels();
 	AtEOXact_portals();
@@ -916,10 +919,6 @@ CommitTransaction()
 	 * ----------------
 	 */
 	s->state = TRANS_DEFAULT;
-	{							/* want this after commit */
-		if (IsNormalProcessingMode())
-			Async_NotifyAtCommit();
-	}
 
 	/*
 	 * Let others to know about no transaction in progress - vadim
@@ -967,6 +966,7 @@ AbortTransaction()
 	 *	do abort processing
 	 * ----------------
 	 */
+	AtAbort_Notify();
 	CloseSequences();
 	AtEOXact_portals();
 	RecordTransactionAbort();
@@ -982,17 +982,6 @@ AbortTransaction()
 	 * ----------------
 	 */
 	s->state = TRANS_DEFAULT;
-	{
-
-		/*
-		 * We need to do this in case another process notified us while we
-		 * are in the middle of an aborted transaction.  We need to notify
-		 * our frontend after we finish the current transaction. -- jw,
-		 * 1/3/94
-		 */
-		if (IsNormalProcessingMode())
-			Async_NotifyAtAbort();
-	}
 }
 
 /* --------------------------------
@@ -1455,6 +1444,30 @@ UserAbortTransactionBlock()
 	s->blockState = TBLOCK_ENDABORT;
 }
 
+/* --------------------------------
+ *		AbortOutOfAnyTransaction
+ *
+ * This routine is provided for error recovery purposes.  It aborts any
+ * active transaction or transaction block, leaving the system in a known
+ * idle state.
+ * --------------------------------
+ */
+void
+AbortOutOfAnyTransaction()
+{
+	TransactionState s = CurrentTransactionState;
+
+	/*
+	 * Get out of any low-level transaction
+	 */
+	if (s->state != TRANS_DEFAULT)
+		AbortTransaction();
+	/*
+	 * Now reset the high-level state
+	 */
+	s->blockState = TBLOCK_DEFAULT;
+}
+
 bool
 IsTransactionBlock()
 {

src/backend/tcop/postgres.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.90 1998/10/02 01:14:14 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.91 1998/10/06 02:40:01 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -1511,7 +1511,7 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 	if (!IsUnderPostmaster)
 	{
 		puts("\nPOSTGRES backend interactive interface ");
-		puts("$Revision: 1.90 $ $Date: 1998/10/02 01:14:14 $\n");
+		puts("$Revision: 1.91 $ $Date: 1998/10/06 02:40:01 $\n");
 	}
 
 	/* ----------------
@@ -1559,7 +1559,16 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 		ReadyForQuery(whereToSendOutput);
 
 		/* ----------------
-		 *	 (2) read a command.
+		 *	 (2) deal with pending asynchronous NOTIFY from other backends,
+		 *   and enable async.c's signal handler to execute NOTIFY directly.
+		 * ----------------
+		 */
+		QueryCancel = false;	/* forget any earlier CANCEL signal */
+
+		EnableNotifyInterrupt();
+
+		/* ----------------
+		 *	 (3) read a command.
 		 * ----------------
 		 */
 		MemSet(parser_input, 0, MAX_PARSE_BUFFER);
@@ -1569,7 +1578,13 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 		QueryCancel = false;	/* forget any earlier CANCEL signal */
 
 		/* ----------------
-		 *	 (3) process the command.
+		 *	 (4) disable async.c's signal handler.
+		 * ----------------
+		 */
+		DisableNotifyInterrupt();
+
+		/* ----------------
+		 *	 (5) process the command.
 		 * ----------------
 		 */
 		switch (firstchar)
@@ -1640,7 +1655,7 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 		}
 
 		/* ----------------
-		 *	 (4) commit the current transaction
+		 *	 (6) commit the current transaction
 		 *
 		 *	 Note: if we had an empty input buffer, then we didn't
 		 *	 call pg_exec_query, so we don't bother to commit this transaction.

src/backend/utils/misc/trace.c

@@ -70,10 +70,6 @@ static char *opt_names[] = {
 	"syslog",					/* use syslog for error messages */
 	"hostlookup",				/* enable hostname lookup in ps_status */
 	"showportnumber",			/* show port number in ps_status */
-	"notifyunlock",				/* enable unlock of pg_listener after
-								 * notify */
-	"notifyhack"				/* enable notify hack to remove duplicate
-								 * tuples */
 };
 
 /*

src/include/access/xact.h

@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: xact.h,v 1.15 1998/09/01 04:34:35 momjian Exp $
+ * $Id: xact.h,v 1.16 1998/10/06 02:40:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -107,6 +107,7 @@ extern void BeginTransactionBlock(void);
 extern void EndTransactionBlock(void);
 extern bool IsTransactionBlock(void);
 extern void UserAbortTransactionBlock(void);
+extern void AbortOutOfAnyTransaction(void);
 
 extern TransactionId DisabledTransactionId;
 

src/include/commands/async.h

 /*-------------------------------------------------------------------------
  *
  * async.h--
- *
- *
+ *	  Asynchronous notification: NOTIFY, LISTEN, UNLISTEN
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: async.h,v 1.9 1998/09/01 04:35:22 momjian Exp $
+ * $Id: async.h,v 1.10 1998/10/06 02:40:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef ASYNC_H
 #define ASYNC_H
 
-#include <nodes/memnodes.h>
+#include <postgres.h>
 
-extern void Async_NotifyHandler(SIGNAL_ARGS);
+/* notify-related SQL statements */
 extern void Async_Notify(char *relname);
-extern void Async_NotifyAtCommit(void);
-extern void Async_NotifyAtAbort(void);
 extern void Async_Listen(char *relname, int pid);
 extern void Async_Unlisten(char *relname, int pid);
 
-extern GlobalMemory notifyContext;
+/* perform (or cancel) outbound notify processing at transaction commit */
+extern void AtCommit_Notify(void);
+extern void AtAbort_Notify(void);
+
+/* signal handler for inbound notifies (SIGUSR2) */
+extern void Async_NotifyHandler(SIGNAL_ARGS);
+
+/*
+ * enable/disable processing of inbound notifies directly from signal handler.
+ * The enable routine first performs processing of any inbound notifies that
+ * have occurred since the last disable.  These are meant to be called ONLY
+ * from the appropriate places in PostgresMain().
+ */
+extern void EnableNotifyInterrupt(void);
+extern void DisableNotifyInterrupt(void);
 
 #endif	 /* ASYNC_H */

src/include/utils/trace.h

@@ -66,10 +66,6 @@ enum pg_option_enum
 	OPT_SYSLOG,					/* use syslog for error messages */
 	OPT_HOSTLOOKUP,				/* enable hostname lookup in ps_status */
 	OPT_SHOWPORTNUMBER,			/* show port number in ps_status */
-	OPT_NOTIFYUNLOCK,			/* enable unlock of pg_listener after
-								 * notify */
-	OPT_NOTIFYHACK,				/* enable notify hack to remove duplicate
-								 * tuples */
 
 	NUM_PG_OPTIONS				/* must be the last item of enum */
 };