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Revert addition of pg_terminate_backend() because of race conditions.

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This commit is contained in:
Bruce Momjian 2008-04-15 20:28:47 +00:00
parent 2b8a795738
commit 76365960d2
9 changed files with 43 additions and 92 deletions
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11
doc/TODO
View File

@ -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

10
doc/src/FAQ/TODO.html
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@ -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>

19
doc/src/sgml/func.sgml
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@ -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</>
send a query cancel (<systemitem>SIGINT</>) signal to a backend process
identified by process ID. The
process ID of an active backend can be found from
<function>pg_cancel_backend</> sends a query cancel
(<systemitem>SIGINT</>) signal to a backend process identified by
process ID. The 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

9
doc/src/sgml/runtime.sgml
View File

@ -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">

12
src/backend/tcop/postgres.c
View File

@ -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 &&
(!DoingCommandRead || MyProc->terminate))
CritSectionCount == 0 && !DoingCommandRead)
{
/* 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();
}

63
src/backend/utils/adt/misc.c
View File

@ -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);
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);
PG_RETURN_BOOL(pg_signal_backend(PG_GETARG_INT32(0), SIGINT));
}
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

4
src/include/catalog/pg_proc.h
View File

@ -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_ ));

4
src/include/storage/proc.h
View File

@ -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. */

3
src/include/utils/builtins.h
View File

@ -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);