Revert addition of pg_terminate_backend() because of race conditions.

doc/TODO

@@ -20,8 +20,17 @@ http://developer.postgresql.org.
 Administration
 ==============
 
-* -Allow administrators to safely terminate individual sessions either
+* Allow administrators to safely terminate individual sessions either
   via an SQL function or SIGTERM
+
+  Lock table corruption following SIGTERM of an individual backend
+  has been reported in 8.0.  A possible cause was fixed in 8.1, but
+  it is unknown whether other problems exist.  This item mostly
+  requires additional testing rather than of writing any new code.
+
+  http://archives.postgresql.org/pgsql-hackers/2006-08/msg00174.php
+  http://archives.postgresql.org/pgsql-hackers/2007-04/msg00218.php
+
 * Check for unreferenced table files created by transactions that were
   in-progress when the server terminated abruptly
 

doc/src/FAQ/TODO.html

@@ -26,8 +26,16 @@ first.  There is also a developer's wiki at<br/>
 <h1><a name="section_2">Administration</a></h1>
 
 <ul>
-  <li>-<em>Allow administrators to safely terminate individual sessions either</em>
+  <li>Allow administrators to safely terminate individual sessions either
   via an SQL function or SIGTERM
+<p>  Lock table corruption following SIGTERM of an individual backend
+  has been reported in 8.0.  A possible cause was fixed in 8.1, but
+  it is unknown whether other problems exist.  This item mostly
+  requires additional testing rather than of writing any new code.
+</p>
+<p>  <a href="http://archives.postgresql.org/pgsql-hackers/2006-08/msg00174.php">http://archives.postgresql.org/pgsql-hackers/2006-08/msg00174.php</a>
+  <a href="http://archives.postgresql.org/pgsql-hackers/2007-04/msg00218.php">http://archives.postgresql.org/pgsql-hackers/2007-04/msg00218.php</a>
+</p>
   </li><li>Check for unreferenced table files created by transactions that were
   in-progress when the server terminated abruptly
 <p>  <a href="http://archives.postgresql.org/pgsql-patches/2006-06/msg00096.php">http://archives.postgresql.org/pgsql-patches/2006-06/msg00096.php</a>

doc/src/sgml/func.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.431 2008/04/15 13:55:11 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.432 2008/04/15 20:28:46 momjian Exp $ -->
 
  <chapter id="functions">
   <title>Functions and Operators</title>
@@ -11848,9 +11848,6 @@ SELECT set_config('log_statement_stats', 'off', false);
    <indexterm>
     <primary>pg_cancel_backend</primary>
    </indexterm>
-   <indexterm>
-    <primary>pg_terminate_backend</primary>
-   </indexterm>
    <indexterm>
     <primary>pg_reload_conf</primary>
    </indexterm>
@@ -11886,13 +11883,6 @@ SELECT set_config('log_statement_stats', 'off', false);
        <entry><type>boolean</type></entry>
        <entry>Cancel a backend's current query</entry>
       </row>
-      <row>
-       <entry>
-        <literal><function>pg_terminate_backend</function>(<parameter>pid</parameter> <type>int</>)</literal>
-        </entry>
-       <entry><type>boolean</type></entry>
-       <entry>Terminate a backend</entry>
-      </row>
       <row>
        <entry>
         <literal><function>pg_reload_conf</function>()</literal>
@@ -11917,10 +11907,9 @@ SELECT set_config('log_statement_stats', 'off', false);
    </para>
 
    <para>
-    <function>pg_cancel_backend</> and <function>pg_terminate_backend</>
+    <function>pg_cancel_backend</> sends a query cancel
-    send a query cancel (<systemitem>SIGINT</>) signal to a backend process
+    (<systemitem>SIGINT</>) signal to a backend process identified by
-    identified by process ID.  The
+    process ID.  The process ID of an active backend can be found from
-    process ID of an active backend can be found from
     the <structfield>procpid</structfield> column in the
     <structname>pg_stat_activity</structname> view, or by listing the
     <command>postgres</command> processes on the server with

doc/src/sgml/runtime.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.412 2008/04/15 13:55:11 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.413 2008/04/15 20:28:46 momjian Exp $ -->
 
 <chapter Id="runtime">
  <title>Operating System Environment</title>
@@ -1372,13 +1372,6 @@ $ <userinput>kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`</userinput
     well.
    </para>
   </important>
-
-  <para>
-   To terminate a session while allowing other sessions to continue, use
-   <function>pg_terminate_backend()</> (<xref
-   linkend="functions-admin-signal-table">) rather than sending a signal
-   to the child process.
-  </para>
  </sect1>
 
  <sect1 id="preventing-server-spoofing">

src/backend/tcop/postgres.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.549 2008/04/15 13:55:11 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.550 2008/04/15 20:28:46 momjian Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -2541,8 +2541,7 @@ StatementCancelHandler(SIGNAL_ARGS)
 		 * waiting for input, however.
 		 */
 		if (ImmediateInterruptOK && InterruptHoldoffCount == 0 &&
-			CritSectionCount == 0 &&
+			CritSectionCount == 0 && !DoingCommandRead)
-			(!DoingCommandRead || MyProc->terminate))
 		{
 			/* bump holdoff count to make ProcessInterrupts() a no-op */
 			/* until we are done getting ready for it */
@@ -2622,10 +2621,6 @@ ProcessInterrupts(void)
 			ereport(ERROR,
 					(errcode(ERRCODE_QUERY_CANCELED),
 					 errmsg("canceling autovacuum task")));
-		else if (MyProc->terminate)
-			ereport(ERROR,
-					(errcode(ERRCODE_ADMIN_SHUTDOWN),
-					 errmsg("terminating backend due to administrator command")));
 		else
 			ereport(ERROR,
 					(errcode(ERRCODE_QUERY_CANCELED),
@@ -3464,9 +3459,6 @@ PostgresMain(int argc, char *argv[], const char *username)
 		/* We don't have a transaction command open anymore */
 		xact_started = false;
 
-		if (MyProc->terminate)
-			die(SIGINT);
-
 		/* Now we can allow interrupts again */
 		RESUME_INTERRUPTS();
 	}

src/backend/utils/adt/misc.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/misc.c,v 1.60 2008/04/15 13:55:11 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/misc.c,v 1.61 2008/04/15 20:28:46 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -27,7 +27,6 @@
 #include "postmaster/syslogger.h"
 #include "storage/fd.h"
 #include "storage/pmsignal.h"
-#include "storage/proc.h"
 #include "storage/procarray.h"
 #include "utils/builtins.h"
 #include "tcop/tcopprot.h"
@@ -90,7 +89,7 @@ current_query(PG_FUNCTION_ARGS)
  * Functions to send signals to other backends.
  */
 static bool
-pg_signal_check(int pid)
+pg_signal_backend(int pid, int sig)
 {
 	if (!superuser())
 		ereport(ERROR,
@@ -107,16 +106,7 @@ pg_signal_check(int pid)
 				(errmsg("PID %d is not a PostgreSQL server process", pid)));
 		return false;
 	}
-	else
-		return true;
-}
 
-/*
- * Functions to send signals to other backends.
- */
-static bool
-pg_signal_backend(int pid, int sig)
-{
 	/* If we have setsid(), signal the backend's whole process group */
 #ifdef HAVE_SETSID
 	if (kill(-pid, sig))
@@ -135,43 +125,7 @@ pg_signal_backend(int pid, int sig)
 Datum
 pg_cancel_backend(PG_FUNCTION_ARGS)
 {
-	int pid = PG_GETARG_INT32(0);
+	PG_RETURN_BOOL(pg_signal_backend(PG_GETARG_INT32(0), SIGINT));
-	
-	if (pg_signal_check(pid))
-		PG_RETURN_BOOL(pg_signal_backend(pid, SIGINT));
-	else
-		PG_RETURN_BOOL(false);
-}
-
-/*
- *	To cleanly terminate a backend, we set PGPROC(pid)->terminate
- *	then send a cancel signal.  We get ProcArrayLock only when
- *	setting PGPROC->terminate so the function might fail in
- *	several places, but that is fine because in those cases the
- *	backend is already gone.
- */
-Datum
-pg_terminate_backend(PG_FUNCTION_ARGS)
-{
-	int pid = PG_GETARG_INT32(0);
-	volatile PGPROC *term_proc;
-
-	/* Is this the super-user, and can we find the PGPROC entry for the pid? */
-	if (pg_signal_check(pid) && (term_proc = BackendPidGetProc(pid)) != NULL)
-	{
-		LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
-		/* Recheck now that we have the ProcArray lock. */
-		if (term_proc->pid == pid)
-		{
-			term_proc->terminate = true;
-			LWLockRelease(ProcArrayLock);
-			PG_RETURN_BOOL(pg_signal_backend(pid, SIGINT));
-		}
-		else
-			LWLockRelease(ProcArrayLock);
-	}
-
-	PG_RETURN_BOOL(false);
 }
 
 Datum
@@ -215,6 +169,17 @@ pg_rotate_logfile(PG_FUNCTION_ARGS)
 	PG_RETURN_BOOL(true);
 }
 
+#ifdef NOT_USED
+
+/* Disabled in 8.0 due to reliability concerns; FIXME someday */
+Datum
+pg_terminate_backend(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_INT32(pg_signal_backend(PG_GETARG_INT32(0), SIGTERM));
+}
+#endif
+
+
 /* Function to find out which databases make use of a tablespace */
 
 typedef struct

src/include/catalog/pg_proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.490 2008/04/15 13:55:11 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.491 2008/04/15 20:28:46 momjian Exp $
  *
  * NOTES
  *	  The script catalog/genbki.sh reads this file and generates .bki
@@ -3157,8 +3157,6 @@ DESCR("is schema another session's temp schema?");
 
 DATA(insert OID = 2171 ( pg_cancel_backend		PGNSP PGUID 12 1 0 f f t f v 1 16 "23" _null_ _null_ _null_ pg_cancel_backend - _null_ _null_ ));
 DESCR("cancel a server process' current query");
-DATA(insert OID = 2096 ( pg_terminate_backend		PGNSP PGUID 12 1 0 f f t f v 1 16 "23" _null_ _null_ _null_ pg_terminate_backend - _null_ _null_ ));
-DESCR("terminate a server process");
 DATA(insert OID = 2172 ( pg_start_backup		PGNSP PGUID 12 1 0 f f t f v 1 25 "25" _null_ _null_ _null_ pg_start_backup - _null_ _null_ ));
 DESCR("prepare for taking an online backup");
 DATA(insert OID = 2173 ( pg_stop_backup			PGNSP PGUID 12 1 0 f f t f v 0 25 "" _null_ _null_ _null_ pg_stop_backup - _null_ _null_ ));

src/include/storage/proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.105 2008/04/15 13:55:12 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.106 2008/04/15 20:28:47 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -91,8 +91,6 @@ struct PGPROC
 
 	bool		inCommit;		/* true if within commit critical section */
 
-	bool		terminate;		/* admin requested termination */
-
 	uint8		vacuumFlags;	/* vacuum-related flags, see above */
 
 	/* Info about LWLock the process is currently waiting for, if any. */

src/include/utils/builtins.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.313 2008/04/15 13:55:12 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.314 2008/04/15 20:28:47 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -416,7 +416,6 @@ extern Datum nonnullvalue(PG_FUNCTION_ARGS);
 extern Datum current_database(PG_FUNCTION_ARGS);
 extern Datum current_query(PG_FUNCTION_ARGS);
 extern Datum pg_cancel_backend(PG_FUNCTION_ARGS);
-extern Datum pg_terminate_backend(PG_FUNCTION_ARGS);
 extern Datum pg_reload_conf(PG_FUNCTION_ARGS);
 extern Datum pg_tablespace_databases(PG_FUNCTION_ARGS);
 extern Datum pg_rotate_logfile(PG_FUNCTION_ARGS);