1 /*
  2  * Copyright (c) 2017, 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 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHLOCK_HPP
 26 #define SHARE_GC_SHENANDOAH_SHENANDOAHLOCK_HPP
 27 
 28 #include "gc/shenandoah/shenandoahPadding.hpp"
 29 #include "memory/allocation.hpp"
 30 #include "runtime/javaThread.hpp"
 31 #include "runtime/safepoint.hpp"
 32 
 33 class ShenandoahLock  {
 34 private:
 35   enum LockState { unlocked = 0, locked = 1 };
 36 
 37   shenandoah_padding(0);
 38   volatile LockState _state;
 39   shenandoah_padding(1);
 40   volatile Thread* _owner;
 41   shenandoah_padding(2);
 42 
 43   template<typename BlockOp>
 44   void contended_lock_internal(JavaThread* java_thread);
 45 
 46 public:
 47   ShenandoahLock() : _state(unlocked), _owner(nullptr) {};
 48 
 49   void lock(bool allow_block_for_safepoint) {
 50     assert(Atomic::load(&_owner) != Thread::current(), "reentrant locking attempt, would deadlock");
 51 
 52     // Try to lock fast, or dive into contended lock handling.
 53     if (Atomic::cmpxchg(&_state, unlocked, locked) != unlocked) {
 54       contended_lock(allow_block_for_safepoint);
 55     }
 56 
 57     assert(Atomic::load(&_state) == locked, "must be locked");
 58     assert(Atomic::load(&_owner) == nullptr, "must not be owned");
 59     DEBUG_ONLY(Atomic::store(&_owner, Thread::current());)
 60   }
 61 
 62   void unlock() {
 63     assert(Atomic::load(&_owner) == Thread::current(), "sanity");
 64     DEBUG_ONLY(Atomic::store(&_owner, (Thread*)nullptr);)
 65     OrderAccess::fence();
 66     Atomic::store(&_state, unlocked);
 67   }
 68 
 69   void contended_lock(bool allow_block_for_safepoint);
 70 
 71   bool owned_by_self() {
 72 #ifdef ASSERT
 73     return _state == locked && _owner == Thread::current();
 74 #else
 75     ShouldNotReachHere();
 76     return false;
 77 #endif
 78   }
 79 };
 80 
 81 class ShenandoahLocker : public StackObj {
 82 private:
 83   ShenandoahLock* const _lock;
 84 public:
 85   ShenandoahLocker(ShenandoahLock* lock, bool allow_block_for_safepoint = false) : _lock(lock) {
 86     if (_lock != nullptr) {
 87       _lock->lock(allow_block_for_safepoint);
 88     }
 89   }
 90 
 91   ~ShenandoahLocker() {
 92     if (_lock != nullptr) {
 93       _lock->unlock();
 94     }
 95   }
 96 };
 97 
 98 class ShenandoahSimpleLock {
 99 private:
100   PlatformMonitor   _lock; // native lock
101 public:
102   ShenandoahSimpleLock();
103 
104   virtual void lock();
105   virtual void unlock();
106 };
107 
108 class ShenandoahReentrantLock : public ShenandoahSimpleLock {
109 private:
110   Thread* volatile      _owner;
111   uint64_t              _count;
112 
113 public:
114   ShenandoahReentrantLock();
115   ~ShenandoahReentrantLock();
116 
117   virtual void lock();
118   virtual void unlock();
119 
120   // If the lock already owned by this thread
121   bool owned_by_self() const ;
122 };
123 
124 class ShenandoahReentrantLocker : public StackObj {
125 private:
126   ShenandoahReentrantLock* const _lock;
127 
128 public:
129   ShenandoahReentrantLocker(ShenandoahReentrantLock* lock) :
130     _lock(lock) {
131     if (_lock != nullptr) {
132       _lock->lock();
133     }
134   }
135 
136   ~ShenandoahReentrantLocker() {
137     if (_lock != nullptr) {
138       assert(_lock->owned_by_self(), "Must be owner");
139       _lock->unlock();
140     }
141   }
142 };
143 
144 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHLOCK_HPP