From a2793f06a5439afbb43c8b79703f632bfa7ed87a Mon Sep 17 00:00:00 2001
From: Bruno Turcksin <bruno.turcksin@gmail.com>
Date: Mon, 22 Jun 2020 16:22:31 +0000
Subject: [PATCH] Fix CUDA build: make insertion_mutex mutable

The constructor of std::shared_lock cannot take a const ref
---
 include/deal.II/base/thread_local_storage.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/deal.II/base/thread_local_storage.h b/include/deal.II/base/thread_local_storage.h
index cd40096a46..1bd0716b60 100644
--- a/include/deal.II/base/thread_local_storage.h
+++ b/include/deal.II/base/thread_local_storage.h
@@ -248,9 +248,9 @@ namespace Threads
      * (https://en.wikipedia.org/wiki/Readers%E2%80%93writer_lock).
      */
 #  ifdef DEAL_II_HAVE_CXX17
-    std::shared_mutex insertion_mutex;
+    mutable std::shared_mutex insertion_mutex;
 #  else
-    std::shared_timed_mutex insertion_mutex;
+    mutable std::shared_timed_mutex insertion_mutex;
 #  endif
 
     /**
-- 
2.39.5