1 /* 2 * Copyright (c) 2018, 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 "runtime/orderAccess.inline.hpp" 27 #include "trace/tracingExport.hpp" 28 29 // Allow lock-free reads of _sampler_thread. 30 Thread* volatile TracingExport::_sampler_thread = NULL; 31 32 Thread* TracingExport::sampler_thread_acquire() { 33 return (Thread*)OrderAccess::load_acquire(&_sampler_thread); 34 } 35 36 void TracingExport::set_sampler_thread_with_lock(Thread* thread) { 37 // Grab Threads_lock to avoid conflicts with Thread-SMR scans. 38 MutexLocker ml(Threads_lock); 39 assert(thread == NULL || _sampler_thread == NULL, "_sampler_thread should not already be set."); 40 // To match with the lock-free load_acquire(): 41 OrderAccess::release_store(&_sampler_thread, thread); 42 }