1 /* 2 * Copyright (c) 2014, 2015, Dynatrace and/or its affiliates. All rights reserved. 3 * 4 * This file is part of the Lock Contention Tracing Subsystem for the HotSpot 5 * Virtual Machine, which is developed at Christian Doppler Laboratory on 6 * Monitoring and Evolution of Very-Large-Scale Software Systems. Please 7 * contact us at <http://mevss.jku.at/> if you need additional information 8 * or have any questions. 9 * 10 * This code is free software; you can redistribute it and/or modify it 11 * under the terms of the GNU General Public License version 2 only, as 12 * published by the Free Software Foundation. 13 * 14 * This code is distributed in the hope that it will be useful, but WITHOUT 15 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 16 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 17 * version 2 for more details (a copy is included in the LICENSE file that 18 * accompanied this code). 19 * 20 * You should have received a copy of the GNU General Public License version 21 * 2 along with this work. If not, see <http://www.gnu.org/licenses/>. 22 * 23 */ 24 25 #include "evtrace/traceBufferQueue.hpp" 26 27 #include "evtrace/traceBuffer.hpp" 28 29 class TraceBufferQueue::SpinLocker: public StackObj { 30 private: 31 TraceBufferQueue * const _queue; 32 33 public: 34 SpinLocker(TraceBufferQueue *q, const char *s) : _queue(q) { 35 Thread::SpinAcquire(&_queue->_mtx, s); 36 } 37 38 ~SpinLocker() { 39 Thread::SpinRelease(&_queue->_mtx); 40 } 41 }; 42 43 TraceBufferQueue::TraceBufferQueue() 44 : _head(NULL), 45 _tail(NULL), 46 _mtx(0), 47 _enqueue_ops(0), 48 _dequeue_ops(0) 49 { 50 } 51 52 TraceBufferQueue::~TraceBufferQueue() { 53 } 54 55 size_t TraceBufferQueue::count() { 56 SpinLocker sl(this, "TraceBufferQueue - count"); 57 return (_enqueue_ops - _dequeue_ops); 58 } 59 60 TraceBuffer * TraceBufferQueue::try_dequeue() { 61 TraceBuffer *buffer = NULL; 62 63 { 64 SpinLocker sl(this, "TraceBufferQueue - try_dequeue"); 65 if (_head != NULL) { 66 buffer = _head; 67 _head = _head->queue_next; 68 if (_head == NULL) { 69 _tail = NULL; 70 } 71 _dequeue_ops++; 72 } 73 } 74 75 if (buffer != NULL) { 76 buffer->queue_next = NULL; 77 } 78 return buffer; 79 } 80 81 void TraceBufferQueue::enqueue(TraceBuffer * const buffer) { 82 assert(buffer != NULL, "sanity"); 83 assert(buffer->queue_next == NULL, "queue linkage"); 84 85 SpinLocker sl(this, "TraceBufferQueue - enqueue"); 86 if (_tail != NULL) { 87 _tail->queue_next = buffer; 88 } else { 89 _head = buffer; 90 } 91 _tail = buffer; 92 _enqueue_ops++; 93 }