From 6597707ea6cedd1fbc6ed232fa2494eb26d74a51 Mon Sep 17 00:00:00 2001
From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Thu, 19 May 2022 19:52:22 -0600
Subject: [PATCH] Use std::call_once() instead of hand-rolling a solution.

---
 source/base/multithread_info.cc | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/source/base/multithread_info.cc b/source/base/multithread_info.cc
index f9d6c984d2..1112b88efe 100644
--- a/source/base/multithread_info.cc
+++ b/source/base/multithread_info.cc
@@ -18,6 +18,7 @@
 
 #include <algorithm>
 #include <cstdlib> // for std::getenv
+#include <mutex>
 #include <thread>
 
 #ifdef DEAL_II_WITH_TBB
@@ -144,14 +145,14 @@ MultithreadInfo::memory_consumption()
 void
 MultithreadInfo::initialize_multithreading()
 {
-  static bool done = false;
-  if (done)
-    return;
-
-  MultithreadInfo::set_thread_limit(numbers::invalid_unsigned_int);
-  done = true;
+  static std::once_flag is_initialized;
+  std::call_once(is_initialized, []() {
+    MultithreadInfo::set_thread_limit(numbers::invalid_unsigned_int);
+  });
 }
 
+
+
 #ifdef DEAL_II_WITH_TASKFLOW
 tf::Executor &
 MultithreadInfo::get_taskflow_executor()
-- 
2.39.5