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Commit894459e

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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 parent6fdba8c commit894459e

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5 files changed

+60
-2
lines changed

5 files changed

+60
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lines changed

‎configure

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -11366,7 +11366,7 @@ fi
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LIBS_including_readline="$LIBS"
1136711367
LIBS=`echo"$LIBS"| sed -e's/-ledit//g' -e's/-lreadline//g'`
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11369-
forac_funcin cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat readlink setproctitle setsid shm_open sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l
11369+
forac_funcin cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstatpthread_is_threaded_npreadlink setproctitle setsid shm_open sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l
1137011370
do:
1137111371
as_ac_var=`$as_echo"ac_cv_func_$ac_func"|$as_tr_sh`
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ac_fn_c_check_func"$LINENO""$ac_func""$as_ac_var"

‎configure.in

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1265,7 +1265,7 @@ 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'`
12671267

1268-
AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat readlink setproctitle setsid shm_open sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l])
1268+
AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstatpthread_is_threaded_npreadlink setproctitle setsid shm_open sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l])
12691269

12701270
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
@@ -87,6 +87,10 @@
8787
#include<dns_sd.h>
8888
#endif
8989

90+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
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#include<pthread.h>
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#endif
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9094
#include"access/transam.h"
9195
#include"access/xlog.h"
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#include"bootstrap/bootstrap.h"
@@ -1200,6 +1204,24 @@ PostmasterMain(int argc, char *argv[])
12001204
*/
12011205
RemovePgTempFiles();
12021206

1207+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
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1209+
/*
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* On Darwin, libintl replaces setlocale() with a version that calls
1211+
* CFLocaleCopyCurrent() when its second argument is "" and every relevant
1212+
* environment variable is unset or empty. CFLocaleCopyCurrent() makes
1213+
* the process multithreaded. The postmaster calls sigprocmask() and
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* calls fork() without an immediate exec(), both of which have undefined
1215+
* 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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*/
1218+
if (pthread_is_threaded_np()!=0)
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ereport(LOG,
1220+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1221+
errmsg("postmaster became multithreaded during startup"),
1222+
errhint("Set the LC_ALL environment variable to a valid locale.")));
1223+
#endif
1224+
12031225
/*
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* Remember postmaster startup time
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*/
@@ -1657,6 +1679,15 @@ ServerLoop(void)
16571679
last_touch_time=now;
16581680
}
16591681

1682+
#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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*/
1688+
Assert(pthread_is_threaded_np()==0);
1689+
#endif
1690+
16601691
/*
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* If we already sent SIGQUIT to children and they are slow to shut
16621693
* down, it's time to send them SIGKILL. This doesn't happen
@@ -4745,6 +4776,18 @@ SubPostmasterMain(int argc, char *argv[])
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staticvoid
47464777
ExitPostmaster(intstatus)
47474778
{
4779+
#ifdefHAVE_PTHREAD_IS_THREADED_NP
4780+
4781+
/*
4782+
* There is no known cause for a postmaster to become multithreaded after
4783+
* startup. Recheck to account for the possibility of unknown causes.
4784+
*/
4785+
if (pthread_is_threaded_np()!=0)
4786+
ereport(LOG,
4787+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
4788+
errmsg("postmaster became multithreaded")));
4789+
#endif
4790+
47484791
/* should cleanup shared memory and kill all backends */
47494792

47504793
/*

‎src/common/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,"");
560561

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

‎src/include/pg_config.h.in

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -394,6 +394,9 @@
394394
/* Define to 1 if the PS_STRINGS thing exists. */
395395
#undef HAVE_PS_STRINGS
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397+
/* Define to 1 if you have the `pthread_is_threaded_np' function. */
398+
#undef HAVE_PTHREAD_IS_THREADED_NP
399+
397400
/* Define to 1 if you have the <pwd.h> header file. */
398401
#undef HAVE_PWD_H
399402

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