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Commit2e49461

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On Darwin, detect and report a multithreaded postmaster.
Darwin --enable-nls builds use a substitute setlocale() that may start athread. Buildfarm member orangutan experienced BackendList corruptionon account of different postmaster threads executing signal handlerssimultaneously. Furthermore, a multithreaded postmaster risks undefinedbehavior from sigprocmask() and fork(). Emit LOG messages about theproblem and its workaround. Back-patch to 9.0 (all supported versions).
1 parent3580397 commit2e49461

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5 files changed

+61
-2
lines changed

5 files changed

+61
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lines changed

‎configure

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -18839,7 +18839,8 @@ LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
1883918839

1884018840

1884118841

18842-
for ac_func in cbrt dlopen fcvt fdatasync getifaddrs getpeereid getpeerucred getrlimit memmove poll pstat readlink scandir setproctitle setsid sigprocmask symlink sysconf towlower utime utimes waitpid wcstombs
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18843+
for ac_func in cbrt dlopen fcvt fdatasync getifaddrs getpeereid getpeerucred getrlimit memmove poll pstat pthread_is_threaded_np readlink scandir setproctitle setsid sigprocmask symlink sysconf towlower utime utimes waitpid wcstombs
1884318844
do
1884418845
as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
1884518846
{ $as_echo "$as_me:$LINENO: checking for $ac_func" >&5

‎configure.in

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1210,7 +1210,7 @@ PGAC_FUNC_GETTIMEOFDAY_1ARG
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LIBS_including_readline="$LIBS"
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LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
12121212

1213-
AC_CHECK_FUNCS([cbrt dlopen fcvt fdatasync getifaddrs getpeereid getpeerucred getrlimit memmove poll pstat readlink scandir setproctitle setsid sigprocmask symlink sysconf towlower utime utimes waitpid wcstombs])
1213+
AC_CHECK_FUNCS([cbrt dlopen fcvt fdatasync getifaddrs getpeereid getpeerucred getrlimit memmove poll pstatpthread_is_threaded_npreadlink scandir setproctitle setsid sigprocmask symlink sysconf towlower utime utimes waitpid wcstombs])
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12151215
AC_REPLACE_FUNCS(fseeko)
12161216
case $host_os in

‎src/backend/postmaster/postmaster.c

Lines changed: 43 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -92,6 +92,10 @@
9292
#include<dns_sd.h>
9393
#endif
9494

95+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
96+
#include<pthread.h>
97+
#endif
98+
9599
#include"access/transam.h"
96100
#include"access/xlog.h"
97101
#include"bootstrap/bootstrap.h"
@@ -1081,6 +1085,24 @@ PostmasterMain(int argc, char *argv[])
10811085
}
10821086
load_ident();
10831087

1088+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
1089+
1090+
/*
1091+
* On Darwin, libintl replaces setlocale() with a version that calls
1092+
* CFLocaleCopyCurrent() when its second argument is "" and every relevant
1093+
* environment variable is unset or empty. CFLocaleCopyCurrent() makes
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* the process multithreaded. The postmaster calls sigprocmask() and
1095+
* calls fork() without an immediate exec(), both of which have undefined
1096+
* behavior in a multithreaded program. A multithreaded postmaster is the
1097+
* normal case on Windows, which offers neither fork() nor sigprocmask().
1098+
*/
1099+
if (pthread_is_threaded_np()!=0)
1100+
ereport(LOG,
1101+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1102+
errmsg("postmaster became multithreaded during startup"),
1103+
errhint("Set the LC_ALL environment variable to a valid locale.")));
1104+
#endif
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10841106
/*
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* Remember postmaster startup time
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*/
@@ -1506,6 +1528,15 @@ ServerLoop(void)
15061528
TouchSocketLockFile();
15071529
last_touch_time=now;
15081530
}
1531+
1532+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
1533+
1534+
/*
1535+
* With assertions enabled, check regularly for appearance of
1536+
* additional threads. All builds check at start and exit.
1537+
*/
1538+
Assert(pthread_is_threaded_np()==0);
1539+
#endif
15091540
}
15101541
}
15111542

@@ -4155,6 +4186,18 @@ SubPostmasterMain(int argc, char *argv[])
41554186
staticvoid
41564187
ExitPostmaster(intstatus)
41574188
{
4189+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
4190+
4191+
/*
4192+
* There is no known cause for a postmaster to become multithreaded after
4193+
* startup. Recheck to account for the possibility of unknown causes.
4194+
*/
4195+
if (pthread_is_threaded_np()!=0)
4196+
ereport(LOG,
4197+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
4198+
errmsg("postmaster became multithreaded")));
4199+
#endif
4200+
41584201
/* should cleanup shared memory and kill all backends */
41594202

41604203
/*

‎src/include/pg_config.h.in

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -387,6 +387,9 @@
387387
/* Define if you have POSIX threads libraries and header files. */
388388
#undef HAVE_PTHREAD
389389

390+
/* Define to 1 if you have the `pthread_is_threaded_np' function. */
391+
#undef HAVE_PTHREAD_IS_THREADED_NP
392+
390393
/* Define to 1 if you have the <pwd.h> header file. */
391394
#undef HAVE_PWD_H
392395

‎src/port/exec.c

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -570,8 +570,20 @@ set_pglocale_pgservice(const char *argv0, const char *app)
570570

571571
/* don't set LC_ALL in the backend */
572572
if (strcmp(app,PG_TEXTDOMAIN("postgres"))!=0)
573+
{
573574
setlocale(LC_ALL,"");
574575

576+
/*
577+
* One could make a case for reproducing here PostmasterMain()'s test
578+
* for whether the process is multithreaded. Unlike the postmaster,
579+
* no frontend program calls sigprocmask() or otherwise provides for
580+
* mutual exclusion between signal handlers. While frontends using
581+
* fork(), if multithreaded, are formally exposed to undefined
582+
* behavior, we have not witnessed a concrete bug. Therefore,
583+
* complaining about multithreading here may be mere pedantry.
584+
*/
585+
}
586+
575587
if (find_my_exec(argv0,my_exec_path)<0)
576588
return;
577589

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