1 /* 2 * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "jfr/recorder/checkpoint/constant/traceid/jfrTraceIdEpoch.hpp" 27 #include "runtime/safepoint.hpp" 28 #include "runtime/orderAccess.inline.hpp" 29 30 // The epoch alternates on each rotation to allow for concurrent tagging. 31 // The regular epoch shift happens only during a safepoint. 32 // The fence is there only for the emergency dump case which happens outside of safepoint. 33 bool JfrTraceIdEpoch::_epoch_state = false; 34 void JfrTraceIdEpoch::shift_epoch() { 35 _epoch_state = !_epoch_state; 36 if (!SafepointSynchronize::is_at_safepoint()) { 37 OrderAccess::fence(); 38 } 39 }