From 1a366d51effd0e9f3301d68c2d3dce09c8c43d1f Mon Sep 17 00:00:00 2001 From: Noah Misch Date: Wed, 7 Jan 2015 22:35:44 -0500 Subject: [PATCH] On Darwin, detect and report a multithreaded postmaster. Darwin --enable-nls builds use a substitute setlocale() that may start a thread. Buildfarm member orangutan experienced BackendList corruption on account of different postmaster threads executing signal handlers simultaneously. Furthermore, a multithreaded postmaster risks undefined behavior from sigprocmask() and fork(). Emit LOG messages about the problem and its workaround. Back-patch to 9.0 (all supported versions). --- configure | 3 +- configure.in | 2 +- src/backend/postmaster/postmaster.c | 43 +++++++++++++++++++++++++++++ src/include/pg_config.h.in | 3 ++ src/port/exec.c | 12 ++++++++ 5 files changed, 61 insertions(+), 2 deletions(-) diff --git a/configure b/configure index 5136270bb29..28526f542fd 100755 --- a/configure +++ b/configure @@ -19833,7 +19833,8 @@ LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'` -for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat readlink setproctitle setsid sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l + +for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat pthread_is_threaded_np readlink setproctitle setsid sigprocmask symlink sync_file_range towlower utime utimes wcstombs wcstombs_l do as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh` { $as_echo "$as_me:$LINENO: checking for $ac_func" >&5 diff --git a/configure.in b/configure.in index e946f6503d2..51f1807f965 100644 --- a/configure.in +++ b/configure.in @@ -1259,7 +1259,7 @@ PGAC_FUNC_GETTIMEOFDAY_1ARG LIBS_including_readline="$LIBS" LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'` -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]) +AC_CHECK_FUNCS([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]) AC_REPLACE_FUNCS(fseeko) case $host_os in diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index 3dbf82b339d..d294f9e0af2 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -91,6 +91,10 @@ #include #endif +#ifdef HAVE_PTHREAD_IS_THREADED_NP +#include +#endif + #include "access/transam.h" #include "access/xlog.h" #include "bootstrap/bootstrap.h" @@ -1233,6 +1237,24 @@ PostmasterMain(int argc, char *argv[]) */ RemovePgTempFiles(); +#ifdef HAVE_PTHREAD_IS_THREADED_NP + + /* + * On Darwin, libintl replaces setlocale() with a version that calls + * CFLocaleCopyCurrent() when its second argument is "" and every relevant + * environment variable is unset or empty. CFLocaleCopyCurrent() makes + * the process multithreaded. The postmaster calls sigprocmask() and + * calls fork() without an immediate exec(), both of which have undefined + * behavior in a multithreaded program. A multithreaded postmaster is the + * normal case on Windows, which offers neither fork() nor sigprocmask(). + */ + if (pthread_is_threaded_np() != 0) + ereport(LOG, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("postmaster became multithreaded during startup"), + errhint("Set the LC_ALL environment variable to a valid locale."))); +#endif + /* * Remember postmaster startup time */ @@ -1675,6 +1697,15 @@ ServerLoop(void) TouchSocketLockFiles(); last_touch_time = now; } + +#ifdef HAVE_PTHREAD_IS_THREADED_NP + + /* + * With assertions enabled, check regularly for appearance of + * additional threads. All builds check at start and exit. + */ + Assert(pthread_is_threaded_np() == 0); +#endif } } @@ -4632,6 +4663,18 @@ SubPostmasterMain(int argc, char *argv[]) static void ExitPostmaster(int status) { +#ifdef HAVE_PTHREAD_IS_THREADED_NP + + /* + * There is no known cause for a postmaster to become multithreaded after + * startup. Recheck to account for the possibility of unknown causes. + */ + if (pthread_is_threaded_np() != 0) + ereport(LOG, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("postmaster became multithreaded"))); +#endif + /* should cleanup shared memory and kill all backends */ /* diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in index ce48dfb691c..b6a6a48807e 100644 --- a/src/include/pg_config.h.in +++ b/src/include/pg_config.h.in @@ -387,6 +387,9 @@ /* Define if you have POSIX threads libraries and header files. */ #undef HAVE_PTHREAD +/* Define to 1 if you have the `pthread_is_threaded_np' function. */ +#undef HAVE_PTHREAD_IS_THREADED_NP + /* Define to 1 if you have the header file. */ #undef HAVE_PWD_H diff --git a/src/port/exec.c b/src/port/exec.c index 8ce7c618ffc..077ac58b2b2 100644 --- a/src/port/exec.c +++ b/src/port/exec.c @@ -556,8 +556,20 @@ set_pglocale_pgservice(const char *argv0, const char *app) /* don't set LC_ALL in the backend */ if (strcmp(app, PG_TEXTDOMAIN("postgres")) != 0) + { setlocale(LC_ALL, ""); + /* + * One could make a case for reproducing here PostmasterMain()'s test + * for whether the process is multithreaded. Unlike the postmaster, + * no frontend program calls sigprocmask() or otherwise provides for + * mutual exclusion between signal handlers. While frontends using + * fork(), if multithreaded, are formally exposed to undefined + * behavior, we have not witnessed a concrete bug. Therefore, + * complaining about multithreading here may be mere pedantry. + */ + } + if (find_my_exec(argv0, my_exec_path) < 0) return;