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Commit5ca4e44

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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 parent603eb79 commit5ca4e44

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5 files changed

+61
-2
lines changed

5 files changed

+61
-2
lines changed

‎configure

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -19302,7 +19302,8 @@ LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
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19305-
for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat readlink setproctitle setsid sigprocmask symlink towlower utime utimes waitpid wcstombs wcstombs_l
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for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat pthread_is_threaded_np readlink setproctitle setsid sigprocmask symlink towlower utime utimes waitpid wcstombs wcstombs_l
1930619307
do
1930719308
as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
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{ $as_echo "$as_me:$LINENO: checking for $ac_func" >&5

‎configure.in

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1241,7 +1241,7 @@ 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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1244-
AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat readlink setproctitle setsid sigprocmask symlink towlower utime utimes waitpid wcstombs wcstombs_l])
1244+
AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstatpthread_is_threaded_npreadlink setproctitle setsid sigprocmask symlink towlower utime utimes waitpid wcstombs wcstombs_l])
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AC_REPLACE_FUNCS(fseeko)
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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"
@@ -1105,6 +1109,24 @@ PostmasterMain(int argc, char *argv[])
11051109
*/
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RemovePgTempFiles();
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1112+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
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/*
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* On Darwin, libintl replaces setlocale() with a version that calls
1116+
* CFLocaleCopyCurrent() when its second argument is "" and every relevant
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* 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
1120+
* behavior in a multithreaded program. A multithreaded postmaster is the
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* normal case on Windows, which offers neither fork() nor sigprocmask().
1122+
*/
1123+
if (pthread_is_threaded_np()!=0)
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ereport(LOG,
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(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
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errmsg("postmaster became multithreaded during startup"),
1127+
errhint("Set the LC_ALL environment variable to a valid locale.")));
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#endif
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11081130
/*
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* Remember postmaster startup time
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*/
@@ -1441,6 +1463,15 @@ ServerLoop(void)
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TouchSocketLockFile();
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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.
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*/
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Assert(pthread_is_threaded_np()==0);
1474+
#endif
14441475
}
14451476
}
14461477

@@ -4211,6 +4242,18 @@ SubPostmasterMain(int argc, char *argv[])
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staticvoid
42124243
ExitPostmaster(intstatus)
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{
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#ifdefHAVE_PTHREAD_IS_THREADED_NP
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/*
4248+
* There is no known cause for a postmaster to become multithreaded after
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* startup. Recheck to account for the possibility of unknown causes.
4250+
*/
4251+
if (pthread_is_threaded_np()!=0)
4252+
ereport(LOG,
4253+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
4254+
errmsg("postmaster became multithreaded")));
4255+
#endif
4256+
42144257
/* should cleanup shared memory and kill all backends */
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42164259
/*

‎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
@@ -571,8 +571,20 @@ set_pglocale_pgservice(const char *argv0, const char *app)
571571

572572
/* don't set LC_ALL in the backend */
573573
if (strcmp(app,PG_TEXTDOMAIN("postgres"))!=0)
574+
{
574575
setlocale(LC_ALL,"");
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577+
/*
578+
* One could make a case for reproducing here PostmasterMain()'s test
579+
* for whether the process is multithreaded. Unlike the postmaster,
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* no frontend program calls sigprocmask() or otherwise provides for
581+
* mutual exclusion between signal handlers. While frontends using
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* fork(), if multithreaded, are formally exposed to undefined
583+
* behavior, we have not witnessed a concrete bug. Therefore,
584+
* complaining about multithreading here may be mere pedantry.
585+
*/
586+
}
587+
576588
if (find_my_exec(argv0,my_exec_path)<0)
577589
return;
578590

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