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/safepoint.hpp"
  31 #include "runtime/thread.hpp"
  32 
  33 class ShenandoahLock  {
  34 private:
  35   enum LockState { unlocked = 0, locked = 1 };
  36 
  37   shenandoah_padding(0);
  38   volatile int _state;
  39   shenandoah_padding(1);
  40   volatile Thread* _owner;
  41   shenandoah_padding(2);
  42 
  43 public:
  44   ShenandoahLock() : _state(unlocked), _owner(NULL) {};
  45 
  46   void lock() {
  47 #ifdef ASSERT
  48     assert(_owner != Thread::current(), "reentrant locking attempt, would deadlock");
  49 #endif
  50     Thread::SpinAcquire(&_state, "Shenandoah Heap Lock");
  51 #ifdef ASSERT
  52     assert(_state == locked, "must be locked");
  53     assert(_owner == NULL, "must not be owned");
  54     _owner = Thread::current();
  55 #endif
  56   }
  57 
  58   void unlock() {
  59 #ifdef ASSERT
  60     assert (_owner == Thread::current(), "sanity");
  61     _owner = NULL;
  62 #endif
  63     Thread::SpinRelease(&_state);
  64   }
  65 
  66   bool owned_by_self() {
  67 #ifdef ASSERT
  68     return _state == locked && _owner == Thread::current();
  69 #else
  70     ShouldNotReachHere();
  71     return false;
  72 #endif
  73   }
  74 };
  75 
  76 class ShenandoahLocker : public StackObj {
  77 private:
  78   ShenandoahLock* const _lock;
  79 public:
  80   ShenandoahLocker(ShenandoahLock* lock) : _lock(lock) {
  81     if (_lock != NULL) {
  82       _lock->lock();
  83     }
  84   }
  85 
  86   ~ShenandoahLocker() {
  87     if (_lock != NULL) {
  88       _lock->unlock();
  89     }
  90   }
  91 };
  92 
  93 class ShenandoahSimpleLock {
  94 private:
  95   os::PlatformMonitor   _lock; // native lock
  96 public:
  97   ShenandoahSimpleLock();
  98 
  99   virtual void lock();
 100   virtual void unlock();
 101 };
 102 
 103 class ShenandoahReentrantLock : public ShenandoahSimpleLock {
 104 private:
 105   Thread* volatile      _owner;
 106   uint64_t              _count;
 107 
 108 public:
 109   ShenandoahReentrantLock();
 110   ~ShenandoahReentrantLock();
 111 
 112   virtual void lock();
 113   virtual void unlock();
 114 
 115   // If the lock already owned by this thread
 116   bool owned_by_self() const ;
 117 };
 118 
 119 class ShenandoahReentrantLocker : public StackObj {
 120 private:
 121   ShenandoahReentrantLock* const _lock;
 122 
 123 public:
 124   ShenandoahReentrantLocker(ShenandoahReentrantLock* lock) :
 125     _lock(lock) {
 126     if (_lock != NULL) {
 127       _lock->lock();
 128     }
 129   }
 130 
 131   ~ShenandoahReentrantLocker() {
 132     if (_lock != NULL) {
 133       assert(_lock->owned_by_self(), "Must be owner");
 134       _lock->unlock();
 135     }
 136   }
 137 };
 138 
 139 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHLOCK_HPP