--- a/src/hotspot/share/gc/shared/stringdedup/stringDedupThread.inline.hpp	Wed Apr 24 19:51:38 2019 -0700
+++ b/src/hotspot/share/gc/shared/stringdedup/stringDedupThread.inline.hpp	Thu Apr 25 08:55:49 2019 +0200
@@ -33,7 +33,11 @@
 void StringDedupThreadImpl<S>::do_deduplication() {
   S total_stat;
 
-  deduplicate_shared_strings(&total_stat);
+  {
+    // Block safepoints while deduplicating shared strings
+    SuspendibleThreadSetJoiner sts_join;
+    deduplicate_shared_strings(&total_stat);
+  }
 
   // Main loop
   for (;;) {