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Commit1a366d5

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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 parent230865e commit1a366d5

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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
@@ -19833,7 +19833,8 @@ LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
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1983419834

1983519835

19836-
for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat readlink setproctitle setsid sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l
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19837+
for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat pthread_is_threaded_np readlink setproctitle setsid sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l
1983719838
do
1983819839
as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
1983919840
{ $as_echo "$as_me:$LINENO: checking for $ac_func" >&5

‎configure.in

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1259,7 +1259,7 @@ 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'`
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1262-
AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat readlink setproctitle setsid sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l])
1262+
AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstatpthread_is_threaded_npreadlink setproctitle setsid sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l])
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AC_REPLACE_FUNCS(fseeko)
12651265
case $host_os in

‎src/backend/postmaster/postmaster.c

Lines changed: 43 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -91,6 +91,10 @@
9191
#include<dns_sd.h>
9292
#endif
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94+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
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#include<pthread.h>
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#endif
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9498
#include"access/transam.h"
9599
#include"access/xlog.h"
96100
#include"bootstrap/bootstrap.h"
@@ -1233,6 +1237,24 @@ PostmasterMain(int argc, char *argv[])
12331237
*/
12341238
RemovePgTempFiles();
12351239

1240+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
1241+
1242+
/*
1243+
* On Darwin, libintl replaces setlocale() with a version that calls
1244+
* CFLocaleCopyCurrent() when its second argument is "" and every relevant
1245+
* environment variable is unset or empty. CFLocaleCopyCurrent() makes
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* the process multithreaded. The postmaster calls sigprocmask() and
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* calls fork() without an immediate exec(), both of which have undefined
1248+
* behavior in a multithreaded program. A multithreaded postmaster is the
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* normal case on Windows, which offers neither fork() nor sigprocmask().
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*/
1251+
if (pthread_is_threaded_np()!=0)
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ereport(LOG,
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(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1254+
errmsg("postmaster became multithreaded during startup"),
1255+
errhint("Set the LC_ALL environment variable to a valid locale.")));
1256+
#endif
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/*
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* Remember postmaster startup time
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*/
@@ -1675,6 +1697,15 @@ ServerLoop(void)
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TouchSocketLockFiles();
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last_touch_time=now;
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}
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#ifdefHAVE_PTHREAD_IS_THREADED_NP
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/*
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* With assertions enabled, check regularly for appearance of
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* additional threads. All builds check at start and exit.
1706+
*/
1707+
Assert(pthread_is_threaded_np()==0);
1708+
#endif
16781709
}
16791710
}
16801711

@@ -4632,6 +4663,18 @@ SubPostmasterMain(int argc, char *argv[])
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staticvoid
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ExitPostmaster(intstatus)
46344665
{
4666+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
4667+
4668+
/*
4669+
* There is no known cause for a postmaster to become multithreaded after
4670+
* startup. Recheck to account for the possibility of unknown causes.
4671+
*/
4672+
if (pthread_is_threaded_np()!=0)
4673+
ereport(LOG,
4674+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
4675+
errmsg("postmaster became multithreaded")));
4676+
#endif
4677+
46354678
/* should cleanup shared memory and kill all backends */
46364679

46374680
/*

‎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
@@ -556,8 +556,20 @@ set_pglocale_pgservice(const char *argv0, const char *app)
556556

557557
/* don't set LC_ALL in the backend */
558558
if (strcmp(app,PG_TEXTDOMAIN("postgres"))!=0)
559+
{
559560
setlocale(LC_ALL,"");
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562+
/*
563+
* One could make a case for reproducing here PostmasterMain()'s test
564+
* for whether the process is multithreaded. Unlike the postmaster,
565+
* no frontend program calls sigprocmask() or otherwise provides for
566+
* mutual exclusion between signal handlers. While frontends using
567+
* fork(), if multithreaded, are formally exposed to undefined
568+
* behavior, we have not witnessed a concrete bug. Therefore,
569+
* complaining about multithreading here may be mere pedantry.
570+
*/
571+
}
572+
561573
if (find_my_exec(argv0,my_exec_path)<0)
562574
return;
563575

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