1 /*
   2  * Copyright (c) 2019, 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 #include "precompiled.hpp"
  25 
  26 #include "runtime/os.hpp"
  27 
  28 #include "gc/shenandoah/shenandoahLock.hpp"
  29 #include "runtime/atomic.hpp"
  30 #include "runtime/os.inline.hpp"
  31 #include "runtime/thread.hpp"
  32 
  33 ShenandoahSimpleLock::ShenandoahSimpleLock() {
  34   assert(os::mutex_init_done(), "Too early!");
  35 }
  36 
  37 void ShenandoahSimpleLock::lock() {
  38   _lock.lock();
  39 }
  40 
  41 void ShenandoahSimpleLock::unlock() {
  42   _lock.unlock();
  43 }
  44 
  45 ShenandoahReentrantLock::ShenandoahReentrantLock() :
  46   ShenandoahSimpleLock(), _owner(NULL), _count(0) {
  47   assert(os::mutex_init_done(), "Too early!");
  48 }
  49 
  50 ShenandoahReentrantLock::~ShenandoahReentrantLock() {
  51   assert(_count == 0, "Unbalance");
  52 }
  53 
  54 void ShenandoahReentrantLock::lock() {
  55   Thread* const thread = Thread::current();
  56   Thread* const owner = Atomic::load(&_owner);
  57 
  58   if (owner != thread) {
  59     ShenandoahSimpleLock::lock();
  60     Atomic::store(thread, &_owner);
  61   }
  62 
  63   _count++;
  64 }
  65 
  66 void ShenandoahReentrantLock::unlock() {
  67   assert(owned_by_self(), "Invalid owner");
  68   assert(_count > 0, "Invalid count");
  69 
  70   _count--;
  71 
  72   if (_count == 0) {
  73     Atomic::store((Thread*)NULL, &_owner);
  74     ShenandoahSimpleLock::unlock();
  75   }
  76 }
  77 
  78 bool ShenandoahReentrantLock::owned_by_self() const {
  79   Thread* const thread = Thread::current();
  80   Thread* const owner = Atomic::load(&_owner);
  81   return owner == thread;
  82 }