--- a/hotspot/src/share/vm/gc/g1/g1CollectedHeap.cpp	Tue Apr 12 14:46:02 2016 -0400
+++ b/hotspot/src/share/vm/gc/g1/g1CollectedHeap.cpp	Wed Apr 13 17:00:54 2016 -0400
@@ -2742,7 +2742,7 @@
   _cmThread->print_on(st);
   st->cr();
   _cm->print_worker_threads_on(st);
-  _cg1r->print_worker_threads_on(st);
+  _cg1r->print_worker_threads_on(st); // also prints the sample thread
   if (G1StringDedup::is_enabled()) {
     G1StringDedup::print_worker_threads_on(st);
   }
@@ -2751,7 +2751,8 @@
 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
   workers()->threads_do(tc);
   tc->do_thread(_cmThread);
-  _cg1r->threads_do(tc);
+  _cm->threads_do(tc);
+  _cg1r->threads_do(tc); // also iterates over the sample thread
   if (G1StringDedup::is_enabled()) {
     G1StringDedup::threads_do(tc);
   }

--- a/hotspot/src/share/vm/gc/g1/g1ConcurrentMark.cpp	Tue Apr 12 14:46:02 2016 -0400
+++ b/hotspot/src/share/vm/gc/g1/g1ConcurrentMark.cpp	Wed Apr 13 17:00:54 2016 -0400
@@ -2112,6 +2112,10 @@
   _parallel_workers->print_worker_threads_on(st);
 }
 
+void G1ConcurrentMark::threads_do(ThreadClosure* tc) const {
+  _parallel_workers->threads_do(tc);
+}
+
 void G1ConcurrentMark::print_on_error(outputStream* st) const {
   st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
       p2i(_prevMarkBitMap), p2i(_nextMarkBitMap));

--- a/hotspot/src/share/vm/gc/g1/g1ConcurrentMark.hpp	Tue Apr 12 14:46:02 2016 -0400
+++ b/hotspot/src/share/vm/gc/g1/g1ConcurrentMark.hpp	Wed Apr 13 17:00:54 2016 -0400
@@ -621,6 +621,7 @@
   void print_summary_info();
 
   void print_worker_threads_on(outputStream* st) const;
+  void threads_do(ThreadClosure* tc) const;
 
   void print_on_error(outputStream* st) const;
 

--- a/hotspot/src/share/vm/runtime/thread.cpp	Tue Apr 12 14:46:02 2016 -0400
+++ b/hotspot/src/share/vm/runtime/thread.cpp	Wed Apr 13 17:00:54 2016 -0400
@@ -818,13 +818,17 @@
 // Thread::print_on_error() is called by fatal error handler. Don't use
 // any lock or allocate memory.
 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
-  if (is_VM_thread())                 st->print("VMThread");
-  else if (is_Compiler_thread())      st->print("CompilerThread");
-  else if (is_Java_thread())          st->print("JavaThread");
-  else if (is_GC_task_thread())       st->print("GCTaskThread");
-  else if (is_Watcher_thread())       st->print("WatcherThread");
-  else if (is_ConcurrentGC_thread())  st->print("ConcurrentGCThread");
-  else                                st->print("Thread");
+  assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
+
+  if (is_VM_thread())                 { st->print("VMThread"); }
+  else if (is_GC_task_thread())       { st->print("GCTaskThread"); }
+  else if (is_Watcher_thread())       { st->print("WatcherThread"); }
+  else if (is_ConcurrentGC_thread())  { st->print("ConcurrentGCThread"); }
+  else                                { st->print("Thread"); }
+
+  if (is_Named_thread()) {
+    st->print(" \"%s\"", name());
+  }
 
   st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
             p2i(stack_end()), p2i(stack_base()));
@@ -4498,6 +4502,36 @@
   st->flush();
 }
 
+void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
+                             int buflen, bool* found_current) {
+  if (this_thread != NULL) {
+    bool is_current = (current == this_thread);
+    *found_current = *found_current || is_current;
+    st->print("%s", is_current ? "=>" : "  ");
+
+    st->print(PTR_FORMAT, p2i(this_thread));
+    st->print(" ");
+    this_thread->print_on_error(st, buf, buflen);
+    st->cr();
+  }
+}
+
+class PrintOnErrorClosure : public ThreadClosure {
+  outputStream* _st;
+  Thread* _current;
+  char* _buf;
+  int _buflen;
+  bool* _found_current;
+ public:
+  PrintOnErrorClosure(outputStream* st, Thread* current, char* buf,
+                      int buflen, bool* found_current) :
+   _st(st), _current(current), _buf(buf), _buflen(buflen), _found_current(found_current) {}
+
+  virtual void do_thread(Thread* thread) {
+    Threads::print_on_error(thread, _st, _current, _buf, _buflen, _found_current);
+  }
+};
+
 // Threads::print_on_error() is called by fatal error handler. It's possible
 // that VM is not at safepoint and/or current thread is inside signal handler.
 // Don't print stack trace, as the stack may not be walkable. Don't allocate
@@ -4507,40 +4541,17 @@
   bool found_current = false;
   st->print_cr("Java Threads: ( => current thread )");
   ALL_JAVA_THREADS(thread) {
-    bool is_current = (current == thread);
-    found_current = found_current || is_current;
-
-    st->print("%s", is_current ? "=>" : "  ");
-
-    st->print(PTR_FORMAT, p2i(thread));
-    st->print(" ");
-    thread->print_on_error(st, buf, buflen);
-    st->cr();
+    print_on_error(thread, st, current, buf, buflen, &found_current);
   }
   st->cr();
 
   st->print_cr("Other Threads:");
-  if (VMThread::vm_thread()) {
-    bool is_current = (current == VMThread::vm_thread());
-    found_current = found_current || is_current;
-    st->print("%s", current == VMThread::vm_thread() ? "=>" : "  ");
-
-    st->print(PTR_FORMAT, p2i(VMThread::vm_thread()));
-    st->print(" ");
-    VMThread::vm_thread()->print_on_error(st, buf, buflen);
-    st->cr();
-  }
-  WatcherThread* wt = WatcherThread::watcher_thread();
-  if (wt != NULL) {
-    bool is_current = (current == wt);
-    found_current = found_current || is_current;
-    st->print("%s", is_current ? "=>" : "  ");
-
-    st->print(PTR_FORMAT, p2i(wt));
-    st->print(" ");
-    wt->print_on_error(st, buf, buflen);
-    st->cr();
-  }
+  print_on_error(VMThread::vm_thread(), st, current, buf, buflen, &found_current);
+  print_on_error(WatcherThread::watcher_thread(), st, current, buf, buflen, &found_current);
+
+  PrintOnErrorClosure print_closure(st, current, buf, buflen, &found_current);
+  Universe::heap()->gc_threads_do(&print_closure);
+
   if (!found_current) {
     st->cr();
     st->print("=>" PTR_FORMAT " (exited) ", p2i(current));

--- a/hotspot/src/share/vm/runtime/thread.hpp	Tue Apr 12 14:46:02 2016 -0400
+++ b/hotspot/src/share/vm/runtime/thread.hpp	Wed Apr 13 17:00:54 2016 -0400
@@ -2156,6 +2156,8 @@
     print_on(tty, print_stacks, internal_format, false /* no concurrent lock printed */);
   }
   static void print_on_error(outputStream* st, Thread* current, char* buf, int buflen);
+  static void print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
+                             int buflen, bool* found_current);
   static void print_threads_compiling(outputStream* st, char* buf, int buflen);
 
   // Get Java threads that are waiting to enter a monitor. If doLock