diff -r 80e7764e4d09 -r 129d60b5dac7 src/hotspot/share/runtime/thread.cpp
--- a/src/hotspot/share/runtime/thread.cpp	Thu Apr 12 14:27:23 2018 +0200
+++ b/src/hotspot/share/runtime/thread.cpp	Thu Apr 12 09:03:46 2018 -0400
@@ -106,6 +106,7 @@
 #include "services/threadService.hpp"
 #include "trace/traceMacros.hpp"
 #include "trace/tracing.hpp"
+#include "trace/tracingExport.hpp"
 #include "utilities/align.hpp"
 #include "utilities/copy.hpp"
 #include "utilities/defaultStream.hpp"
@@ -3435,17 +3436,14 @@
 // All JavaThreads
 #define ALL_JAVA_THREADS(X) DO_JAVA_THREADS(ThreadsSMRSupport::get_java_thread_list(), X)
 
-// All JavaThreads + all non-JavaThreads (i.e., every thread in the system)
-void Threads::threads_do(ThreadClosure* tc) {
-  assert_locked_or_safepoint(Threads_lock);
-  // ALL_JAVA_THREADS iterates through all JavaThreads
-  ALL_JAVA_THREADS(p) {
-    tc->do_thread(p);
-  }
+// All non-JavaThreads (i.e., every non-JavaThread in the system).
+void Threads::non_java_threads_do(ThreadClosure* tc) {
   // Someday we could have a table or list of all non-JavaThreads.
   // For now, just manually iterate through them.
   tc->do_thread(VMThread::vm_thread());
-  Universe::heap()->gc_threads_do(tc);
+  if (Universe::heap() != NULL) {
+    Universe::heap()->gc_threads_do(tc);
+  }
   WatcherThread *wt = WatcherThread::watcher_thread();
   // Strictly speaking, the following NULL check isn't sufficient to make sure
   // the data for WatcherThread is still valid upon being examined. However,
@@ -3458,9 +3456,26 @@
     tc->do_thread(wt);
   }
 
+#if INCLUDE_TRACE
+  Thread* sampler_thread = TracingExport::sampler_thread_acquire();
+  if (sampler_thread != NULL) {
+    tc->do_thread(sampler_thread);
+  }
+#endif
+
   // If CompilerThreads ever become non-JavaThreads, add them here
 }
 
+// All JavaThreads + all non-JavaThreads (i.e., every thread in the system).
+void Threads::threads_do(ThreadClosure* tc) {
+  assert_locked_or_safepoint(Threads_lock);
+  // ALL_JAVA_THREADS iterates through all JavaThreads.
+  ALL_JAVA_THREADS(p) {
+    tc->do_thread(p);
+  }
+  non_java_threads_do(tc);
+}
+
 void Threads::possibly_parallel_threads_do(bool is_par, ThreadClosure* tc) {
   int cp = Threads::thread_claim_parity();
   ALL_JAVA_THREADS(p) {