1 /*
   2  * Copyright (c) 2019, Red Hat, Inc. 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 #include "precompiled.hpp"
  26 
  27 #include "runtime/os.hpp"
  28 
  29 #include "gc/shenandoah/shenandoahLock.hpp"
  30 #include "runtime/atomic.hpp"
  31 #include "runtime/os.inline.hpp"
  32 #include "runtime/thread.hpp"
  33 
  34 ShenandoahSimpleLock::ShenandoahSimpleLock() {
  35   assert(os::mutex_init_done(), "Too early!");
  36 }
  37 
  38 void ShenandoahSimpleLock::lock() {
  39   _lock.lock();
  40 }
  41 
  42 void ShenandoahSimpleLock::unlock() {
  43   _lock.unlock();
  44 }
  45 
  46 ShenandoahReentrantLock::ShenandoahReentrantLock() :
  47   ShenandoahSimpleLock(), _owner(NULL), _count(0) {
  48   assert(os::mutex_init_done(), "Too early!");
  49 }
  50 
  51 ShenandoahReentrantLock::~ShenandoahReentrantLock() {
  52   assert(_count == 0, "Unbalance");
  53 }
  54 
  55 void ShenandoahReentrantLock::lock() {
  56   Thread* const thread = Thread::current();
  57   Thread* const owner = Atomic::load(&_owner);
  58 
  59   if (owner != thread) {
  60     ShenandoahSimpleLock::lock();
  61     Atomic::store(&_owner, thread);
  62   }
  63 
  64   _count++;
  65 }
  66 
  67 void ShenandoahReentrantLock::unlock() {
  68   assert(owned_by_self(), "Invalid owner");
  69   assert(_count > 0, "Invalid count");
  70 
  71   _count--;
  72 
  73   if (_count == 0) {
  74     Atomic::store(&_owner, (Thread*)NULL);
  75     ShenandoahSimpleLock::unlock();
  76   }
  77 }
  78 
  79 bool ShenandoahReentrantLock::owned_by_self() const {
  80   Thread* const thread = Thread::current();
  81   Thread* const owner = Atomic::load(&_owner);
  82   return owner == thread;
  83 }