1 /*

     2  * Copyright (c) 2017, 2018, Red Hat, Inc. All rights reserved.

     3  *

     4  * This code is free software; you can redistribute it and/or modify it

     5  * under the terms of the GNU General Public License version 2 only, as

     6  * published by the Free Software Foundation.

     7  *

     8  * This code is distributed in the hope that it will be useful, but WITHOUT

     9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    11  * version 2 for more details (a copy is included in the LICENSE file that

    12  * accompanied this code).

    13  *

    14  * You should have received a copy of the GNU General Public License version

    15  * 2 along with this work; if not, write to the Free Software Foundation,

    16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    17  *

    18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    19  * or visit www.oracle.com if you need additional information or have any

    20  * questions.

    21  *

    22  */

    23 

    24 #ifndef SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAPLOCK_HPP

    25 #define SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAPLOCK_HPP

    26 

    27 #include "memory/allocation.hpp"

    28 #include "runtime/thread.hpp"

    29 

    30 class ShenandoahHeapLock  {

    31 private:

    32   enum LockState { unlocked = 0, locked = 1 };

    33 

    34   DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile int));

    35   volatile int _state;

    36   DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile Thread*));

    37   volatile Thread* _owner;

    38   DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, 0);

    39 

    40 public:

    41   ShenandoahHeapLock() : _state(unlocked), _owner(NULL) {};

    42 

    43   void lock() {

    44     Thread::SpinAcquire(&_state, "Shenandoah Heap Lock");

    45 #ifdef ASSERT

    46     assert(_state == locked, "must be locked");

    47     assert(_owner == NULL, "must not be owned");

    48     _owner = Thread::current();

    49 #endif

    50   }

    51 

    52   void unlock() {

    53 #ifdef ASSERT

    54     assert (_owner == Thread::current(), "sanity");

    55     _owner = NULL;

    56 #endif

    57     Thread::SpinRelease(&_state);

    58   }

    59 

    60 #ifdef ASSERT

    61   void assert_owned_by_current_thread() {

    62     assert(_state == locked, "must be locked");

    63     assert(_owner == Thread::current(), "must be owned by current thread");

    64   }

    65 

    66   void assert_not_owned_by_current_thread() {

    67     assert(_owner != Thread::current(), "must be not owned by current thread");

    68   }

    69 

    70   void assert_owned_by_current_thread_or_safepoint() {

    71     Thread* thr = Thread::current();

    72     assert((_state == locked && _owner == thr) ||

    73            (SafepointSynchronize::is_at_safepoint() && thr->is_VM_thread()),

    74            "must own heap lock or by VM thread at safepoint");

    75   }

    76 #endif

    77 };

    78 

    79 class ShenandoahHeapLocker : public StackObj {

    80 private:

    81   ShenandoahHeapLock* _lock;

    82 public:

    83   ShenandoahHeapLocker(ShenandoahHeapLock* lock) {

    84     _lock = lock;

    85     _lock->lock();

    86   }

    87 

    88   ~ShenandoahHeapLocker() {

    89     _lock->unlock();

    90   }

    91 };

    92 

    93 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAPLOCK_HPP