1 /*

     2  * Copyright (c) 2014, 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 #ifndef SHARE_VM_JFR_UTILITIES_JFRTRYLOCK_HPP

    26 #define SHARE_VM_JFR_UTILITIES_JFRTRYLOCK_HPP

    27 

    28 #include "runtime/atomic.hpp"

    29 #include "runtime/orderAccess.hpp"

    30 #include "runtime/mutexLocker.hpp"

    31 #include "utilities/debug.hpp"

    32 

    33 class JfrTryLock {

    34  private:

    35   volatile int* const _lock;

    36   bool _has_lock;

    37 

    38  public:

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

    40 

    41   ~JfrTryLock() {

    42     if (_has_lock) {

    43       OrderAccess::fence();

    44       *_lock = 0;

    45     }

    46   }

    47 

    48   bool has_lock() const {

    49     return _has_lock;

    50   }

    51 };

    52 

    53 class JfrMonitorTryLock : public StackObj {

    54  private:

    55   Monitor* _lock;

    56   bool _acquired;

    57 

    58  public:

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

    60 

    61   ~JfrMonitorTryLock() {

    62     if (_acquired) {

    63       assert(_lock->owned_by_self(), "invariant");

    64       _lock->unlock();

    65     }

    66   }

    67 

    68   bool acquired() const {

    69     return _acquired;

    70   }

    71 

    72 };

    73 

    74 #endif // SHARE_VM_JFR_UTILITIES_JFRTRYLOCK_HPP