*** old/src/share/vm/gc_implementation/shared/suspendibleThreadSet.cpp	Tue Apr 14 13:12:07 2015
--- new/src/share/vm/gc_implementation/shared/suspendibleThreadSet.cpp	Tue Apr 14 13:12:07 2015

*** 1,7 ****
--- 1,7 ----
  /*
!  * Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.

*** 31,57 ****
--- 31,64 ----
  uint   SuspendibleThreadSet::_nthreads_stopped  = 0;
  bool   SuspendibleThreadSet::_suspend_all       = false;
  double SuspendibleThreadSet::_suspend_all_start = 0.0;
  
  void SuspendibleThreadSet::join() {
+   assert(!Thread::current()->is_suspendible_thread(),
+     "Thread already joined");
    MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
    while (_suspend_all) {
      ml.wait(Mutex::_no_safepoint_check_flag);
    }
    _nthreads++;
+   DEBUG_ONLY(Thread::current()->set_suspendible_thread();)
  }
  
  void SuspendibleThreadSet::leave() {
+   assert(Thread::current()->is_suspendible_thread(),
+     "Thread not joined");
    MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
    assert(_nthreads > 0, "Invalid");
+   DEBUG_ONLY(Thread::current()->clear_suspendible_thread());
    _nthreads--;
    if (_suspend_all) {
      ml.notify_all();
    }
  }
  
  void SuspendibleThreadSet::yield() {
+   assert(Thread::current()->is_suspendible_thread(), "Must have joined");
    if (_suspend_all) {
      MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
      if (_suspend_all) {
        _nthreads_stopped++;
        if (_nthreads_stopped == _nthreads) {