/*

 * Copyright (c) 2016, 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

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 */

#include "precompiled.hpp"

#include "jfr/recorder/checkpoint/types/traceid/jfrTraceIdEpoch.hpp"

#include "runtime/safepoint.hpp"

#include "runtime/orderAccess.inline.hpp"

// Alternating epochs on each rotation allow for concurrent tagging.

// The regular epoch shift happens only during a safepoint.

// The fence is there only for the emergency dump case which happens outside of safepoint.

bool JfrTraceIdEpoch::_epoch_state = false;

void JfrTraceIdEpoch::shift_epoch() {

  _epoch_state = !_epoch_state;

  if (!SafepointSynchronize::is_at_safepoint()) {

    OrderAccess::fence();

  }

}