/*

 * Copyright (c) 2018, 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.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "runtime/orderAccess.inline.hpp"

#include "trace/tracingExport.hpp"

// Allow lock-free reads of _sampler_thread.

Thread* volatile TracingExport::_sampler_thread = NULL;

Thread* TracingExport::sampler_thread_acquire() {

  return (Thread*)OrderAccess::load_acquire(&_sampler_thread);

}

void TracingExport::set_sampler_thread_with_lock(Thread* thread) {

  // Grab Threads_lock to avoid conflicts with Thread-SMR scans.

  MutexLocker ml(Threads_lock);

  assert(thread == NULL || _sampler_thread == NULL, "_sampler_thread should not already be set.");

  // To match with the lock-free load_acquire():

  OrderAccess::release_store(&_sampler_thread, thread);

}