src/hotspot/share/jfr/utilities/jfrTryLock.hpp

/*
 * Copyright (c) 2014, 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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#ifndef SHARE_VM_JFR_UTILITIES_JFRTRYLOCK_HPP
#define SHARE_VM_JFR_UTILITIES_JFRTRYLOCK_HPP

#include "runtime/atomic.hpp"
#include "runtime/orderAccess.hpp"
#include "runtime/mutexLocker.hpp"
#include "utilities/debug.hpp"

class JfrTryLock {
 private:
  volatile int* const _lock;
  bool _has_lock;

 public:
  JfrTryLock(volatile int* lock) : _lock(lock), _has_lock(Atomic::cmpxchg(1, lock, 0) == 0) {}

  ~JfrTryLock() {
    if (_has_lock) {
      OrderAccess::fence();
      *_lock = 0;
    }
  }

  bool has_lock() const {
    return _has_lock;
  }
};

class JfrMonitorTryLock : public StackObj {
 private:
  Monitor* _lock;
  bool _acquired;

 public:
  JfrMonitorTryLock(Monitor* lock) : _lock(lock), _acquired(lock->try_lock()) {}

  ~JfrMonitorTryLock() {
    if (_acquired) {
      assert(_lock->owned_by_self(), "invariant");
      _lock->unlock();
    }
  }

  bool acquired() const {
    return _acquired;
  }

};

#endif // SHARE_VM_JFR_UTILITIES_JFRTRYLOCK_HPP