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Commit8f5500e

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Make it reasonably safe to use pg_ctl to start the postmaster from a boot-time
script.To do this, have pg_ctl pass down its parent shell's PID in an environmentvariable PG_GRANDPARENT_PID, and teach CreateLockFile() to disregard that PIDas a false match if it finds it in postmaster.pid. This allows us to copewith one level of postgres-owned shell process even with pg_ctl in the way,so it's just as safe as starting the postmaster directly. You still have tobe careful about how you write the initscript though.Adjust the comments in contrib/start-scripts/ to not deprecate use ofpg_ctl. Also, fix the ROTATELOGS option in the OSX script, which wasindulging in exactly the sort of unsafe coding that renders this fixpointless :-(. A pipe inside the "sudo" will probably result in morethan one postgres-owned process hanging around.
1 parent0e3f0cb commit8f5500e

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5 files changed

+77
-38
lines changed

5 files changed

+77
-38
lines changed

‎contrib/start-scripts/freebsd

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
# Created through merger of the Linux start script by Ryan Kirkpatrick
77
# and the script in the FreeBSD ports collection.
88

9-
# $PostgreSQL: pgsql/contrib/start-scripts/freebsd,v 1.4 2004/10/01 18:30:21 tgl Exp $
9+
# $PostgreSQL: pgsql/contrib/start-scripts/freebsd,v 1.5 2009/08/27 16:59:38 tgl Exp $
1010

1111
## EDIT FROM HERE
1212

@@ -27,9 +27,9 @@ PGLOG="$PGDATA/serverlog"
2727
# The path that is to be used for the script
2828
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
2929

30-
# What to use to start up the postmaster (we do NOT use pg_ctl for this,
31-
#as it adds no value and can cause the postmaster to misrecognize a stale
32-
#lock file)
30+
# What to use to start up the postmaster. (If you want the script to wait
31+
#until the server has started, you could use "pg_ctl start -w" here.
32+
#But without -w, pg_ctl adds no value.)
3333
DAEMON="$prefix/bin/postmaster"
3434

3535
# What to use to shut down the postmaster

‎contrib/start-scripts/linux

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -24,7 +24,7 @@
2424

2525
# Original author: Ryan Kirkpatrick <pgsql@rkirkpat.net>
2626

27-
# $PostgreSQL: pgsql/contrib/start-scripts/linux,v 1.8 2006/07/13 14:44:33 petere Exp $
27+
# $PostgreSQL: pgsql/contrib/start-scripts/linux,v 1.9 2009/08/27 16:59:38 tgl Exp $
2828

2929
## EDIT FROM HERE
3030

@@ -45,9 +45,9 @@ PGLOG="$PGDATA/serverlog"
4545
# The path that is to be used for the script
4646
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
4747

48-
# What to use to start up the postmaster (we do NOT use pg_ctl for this,
49-
#as it adds no value and can cause the postmaster to misrecognize a stale
50-
#lock file)
48+
# What to use to start up the postmaster. (If you want the script to wait
49+
#until the server has started, you could use "pg_ctl start -w" here.
50+
#But without -w, pg_ctl adds no value.)
5151
DAEMON="$prefix/bin/postmaster"
5252

5353
# What to use to shut down the postmaster

‎contrib/start-scripts/osx/PostgreSQL

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -68,9 +68,9 @@ ROTATESEC="604800"
6868
# The path that is to be used for the script
6969
PATH="$prefix/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin"
7070

71-
# What to use to start up the postmaster (we do NOT use pg_ctl for this,
72-
#as it adds no value and can cause the postmaster to misrecognize a stale
73-
#lock file)
71+
# What to use to start up the postmaster. (If you want the script to wait
72+
#until the server has started, you could use "pg_ctl start -w" here.
73+
#But without -w, pg_ctl adds no value.)
7474
DAEMON="$prefix/bin/postmaster"
7575

7676
# What to use to shut down the postmaster
@@ -85,7 +85,7 @@ StartService () {
8585
if ["${POSTGRESQL:=-NO-}"="-YES-" ];then
8686
ConsoleMessage"Starting PostgreSQL database server"
8787
if ["${ROTATELOGS}"="1" ];then
88-
sudo -u$PGUSER sh -c"${DAEMON} -D '${PGDATA}' 2>&1 |${LOGUTIL} '${PGLOG}'${ROTATESEC} &"
88+
sudo -u$PGUSER sh -c"${DAEMON} -D '${PGDATA}'&"2>&1|${LOGUTIL}'${PGLOG}'${ROTATESEC}&
8989
else
9090
sudo -u$PGUSER sh -c"${DAEMON} -D '${PGDATA}' &">>$PGLOG2>&1
9191
fi
@@ -104,7 +104,7 @@ RestartService () {
104104
sudo -u$PGUSER$PGCTL stop -D"$PGDATA" -s -m fast
105105
# should match StartService:
106106
if ["${ROTATELOGS}"="1" ];then
107-
sudo -u$PGUSER sh -c"${DAEMON} -D '${PGDATA}' 2>&1 |${LOGUTIL} '${PGLOG}'${ROTATESEC} &"
107+
sudo -u$PGUSER sh -c"${DAEMON} -D '${PGDATA}'&"2>&1|${LOGUTIL}'${PGLOG}'${ROTATESEC}&
108108
else
109109
sudo -u$PGUSER sh -c"${DAEMON} -D '${PGDATA}' &">>$PGLOG2>&1
110110
fi

‎src/backend/utils/init/miscinit.c

Lines changed: 48 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.176 2009/08/12 20:53:30 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.177 2009/08/27 16:59:38 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -683,7 +683,46 @@ CreateLockFile(const char *filename, bool amPostmaster,
683683
intlen;
684684
intencoded_pid;
685685
pid_tother_pid;
686-
pid_tmy_pid=getpid();
686+
pid_tmy_pid,
687+
my_p_pid,
688+
my_gp_pid;
689+
constchar*envvar;
690+
691+
/*
692+
* If the PID in the lockfile is our own PID or our parent's or
693+
* grandparent's PID, then the file must be stale (probably left over from
694+
* a previous system boot cycle). We need to check this because of the
695+
* likelihood that a reboot will assign exactly the same PID as we had in
696+
* the previous reboot, or one that's only one or two counts larger and
697+
* hence the lockfile's PID now refers to an ancestor shell process. We
698+
* allow pg_ctl to pass down its parent shell PID (our grandparent PID)
699+
* via the environment variable PG_GRANDPARENT_PID; this is so that
700+
* launching the postmaster via pg_ctl can be just as reliable as
701+
* launching it directly. There is no provision for detecting
702+
* further-removed ancestor processes, but if the init script is written
703+
* carefully then all but the immediate parent shell will be root-owned
704+
* processes and so the kill test will fail with EPERM. Note that we
705+
* cannot get a false negative this way, because an existing postmaster
706+
* would surely never launch a competing postmaster or pg_ctl process
707+
* directly.
708+
*/
709+
my_pid=getpid();
710+
711+
#ifndefWIN32
712+
my_p_pid=getppid();
713+
#else
714+
/*
715+
* Windows hasn't got getppid(), but doesn't need it since it's not
716+
* using real kill() either...
717+
*/
718+
my_p_pid=0;
719+
#endif
720+
721+
envvar=getenv("PG_GRANDPARENT_PID");
722+
if (envvar)
723+
my_gp_pid=atoi(envvar);
724+
else
725+
my_gp_pid=0;
687726

688727
/*
689728
* We need a loop here because of race conditions.But don't loop forever
@@ -745,17 +784,11 @@ CreateLockFile(const char *filename, bool amPostmaster,
745784
/*
746785
* Check to see if the other process still exists
747786
*
748-
* If the PID in the lockfile is our own PID or our parent's PID, then
749-
* the file must be stale (probably left over from a previous system
750-
* boot cycle). We need this test because of the likelihood that a
751-
* reboot will assign exactly the same PID as we had in the previous
752-
* reboot.Also, if there is just one more process launch in this
753-
* reboot than in the previous one, the lockfile might mention our
754-
* parent's PID. We can reject that since we'd never be launched
755-
* directly by a competing postmaster.We can't detect grandparent
756-
* processes unfortunately, but if the init script is written
757-
* carefully then all but the immediate parent shell will be
758-
* root-owned processes and so the kill test will fail with EPERM.
787+
* Per discussion above, my_pid, my_p_pid, and my_gp_pid can be
788+
* ignored as false matches.
789+
*
790+
* Normally kill() will fail with ESRCH if the given PID doesn't
791+
* exist.
759792
*
760793
* We can treat the EPERM-error case as okay because that error
761794
* implies that the existing process has a different userid than we
@@ -772,18 +805,9 @@ CreateLockFile(const char *filename, bool amPostmaster,
772805
* Unix socket file belonging to an instance of Postgres being run by
773806
* someone else, at least on machines where /tmp hasn't got a
774807
* stickybit.)
775-
*
776-
* Windows hasn't got getppid(), but doesn't need it since it's not
777-
* using real kill() either...
778-
*
779-
* Normally kill() will fail with ESRCH if the given PID doesn't
780-
* exist.
781808
*/
782-
if (other_pid!=my_pid
783-
#ifndefWIN32
784-
&&other_pid!=getppid()
785-
#endif
786-
)
809+
if (other_pid!=my_pid&&other_pid!=my_p_pid&&
810+
other_pid!=my_gp_pid)
787811
{
788812
if (kill(other_pid,0)==0||
789813
(errno!=ESRCH&&errno!=EPERM))

‎src/bin/pg_ctl/pg_ctl.c

Lines changed: 16 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,7 @@
44
*
55
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
66
*
7-
* $PostgreSQL: pgsql/src/bin/pg_ctl/pg_ctl.c,v 1.111 2009/06/11 14:49:07 momjian Exp $
7+
* $PostgreSQL: pgsql/src/bin/pg_ctl/pg_ctl.c,v 1.112 2009/08/27 16:59:38 tgl Exp $
88
*
99
*-------------------------------------------------------------------------
1010
*/
@@ -672,6 +672,21 @@ do_start(void)
672672
unlimit_core_size();
673673
#endif
674674

675+
/*
676+
* If possible, tell the postmaster our parent shell's PID (see the
677+
* comments in CreateLockFile() for motivation). Windows hasn't got
678+
* getppid() unfortunately.
679+
*/
680+
#ifndefWIN32
681+
{
682+
staticcharenv_var[32];
683+
684+
snprintf(env_var,sizeof(env_var),"PG_GRANDPARENT_PID=%d",
685+
(int)getppid());
686+
putenv(env_var);
687+
}
688+
#endif
689+
675690
exitcode=start_postmaster();
676691
if (exitcode!=0)
677692
{

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