From 0a514e7a8ea2af21d98cbcc2e4da799745786155 Mon Sep 17 00:00:00 2001
From: Tristan Partin <tristan@neon.tech>
Date: Tue, 23 Jan 2024 13:14:33 -0600
Subject: [PATCH v1] Remove pthread_is_threaded_np() checks in postmaster

These checks are not effective for what they are trying to prevent.
Libraries that are preloaded can easily cause this check to fail.
---
 configure                           |  2 +-
 configure.ac                        |  1 -
 meson.build                         |  1 -
 src/backend/postmaster/postmaster.c | 27 ---------------------------
 src/include/pg_config.h.in          |  3 ---
 5 files changed, 1 insertion(+), 33 deletions(-)

diff --git a/configure b/configure
index 70a1968003..e790015c2f 100755
--- a/configure
+++ b/configure
@@ -15573,7 +15573,7 @@ fi
 LIBS_including_readline="$LIBS"
 LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
 
-for ac_func in backtrace_symbols copyfile getifaddrs getpeerucred inet_pton kqueue mbstowcs_l memset_s posix_fallocate ppoll pthread_is_threaded_np setproctitle setproctitle_fast strchrnul strsignal syncfs sync_file_range uselocale wcstombs_l
+for ac_func in backtrace_symbols copyfile getifaddrs getpeerucred inet_pton kqueue mbstowcs_l memset_s posix_fallocate ppoll setproctitle setproctitle_fast strchrnul strsignal syncfs sync_file_range uselocale wcstombs_l
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
 ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
diff --git a/configure.ac b/configure.ac
index 52fd7af446..69356df254 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1784,7 +1784,6 @@ AC_CHECK_FUNCS(m4_normalize([
 	memset_s
 	posix_fallocate
 	ppoll
-	pthread_is_threaded_np
 	setproctitle
 	setproctitle_fast
 	strchrnul
diff --git a/meson.build b/meson.build
index 55184db248..56573c1585 100644
--- a/meson.build
+++ b/meson.build
@@ -2441,7 +2441,6 @@ func_checks = [
   ['ppoll'],
   ['pstat'],
   ['pthread_barrier_wait', {'dependencies': [thread_dep]}],
-  ['pthread_is_threaded_np', {'dependencies': [thread_dep]}],
   ['sem_init', {'dependencies': [rt_dep, thread_dep], 'skip': sema_kind != 'unnamed_posix', 'define': false}],
   ['setproctitle', {'dependencies': [util_dep]}],
   ['setproctitle_fast'],
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index feb471dd1d..40968aadc5 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -1426,24 +1426,6 @@ PostmasterMain(int argc, char *argv[])
 		 */
 	}
 
-#ifdef HAVE_PTHREAD_IS_THREADED_NP
-
-	/*
-	 * On macOS, 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(FATAL,
-				(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
 	 */
@@ -1849,15 +1831,6 @@ ServerLoop(void)
 		if (StartWorkerNeeded || HaveCrashedWorker)
 			maybe_start_bgworkers();
 
-#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
-
 		/*
 		 * Lastly, check to see if it's time to do some things that we don't
 		 * want to do every single time through the loop, because they're a
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 288bb9cb42..922882b26f 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -336,9 +336,6 @@
 /* Define to 1 if you have the `pthread_barrier_wait' function. */
 #undef HAVE_PTHREAD_BARRIER_WAIT
 
-/* Define to 1 if you have the `pthread_is_threaded_np' function. */
-#undef HAVE_PTHREAD_IS_THREADED_NP
-
 /* Have PTHREAD_PRIO_INHERIT. */
 #undef HAVE_PTHREAD_PRIO_INHERIT
 
-- 
Tristan Partin
Neon (https://neon.tech)