src/monitor.h

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef ART_SRC_MONITOR_H_
#define ART_SRC_MONITOR_H_

#include <pthread.h>
#include <stdint.h>

#include <iosfwd>
#include <list>

#include "heap.h"
#include "mutex.h"

namespace art {

/*
 * Monitor shape field. Used to distinguish thin locks from fat locks.
 */
#define LW_SHAPE_THIN 0
#define LW_SHAPE_FAT 1
#define LW_SHAPE_MASK 0x1
#define LW_SHAPE(x) ((x) & LW_SHAPE_MASK)

/*
 * Hash state field.  Used to signify that an object has had its
 * identity hash code exposed or relocated.
 */
#define LW_HASH_STATE_UNHASHED 0
#define LW_HASH_STATE_HASHED 1
#define LW_HASH_STATE_HASHED_AND_MOVED 3
#define LW_HASH_STATE_MASK 0x3
#define LW_HASH_STATE_SHIFT 1
#define LW_HASH_STATE(x) (((x) >> LW_HASH_STATE_SHIFT) & LW_HASH_STATE_MASK)

/*
 * Lock owner field.  Contains the thread id of the thread currently
 * holding the lock.
 */
#define LW_LOCK_OWNER_MASK 0xffff
#define LW_LOCK_OWNER_SHIFT 3
#define LW_LOCK_OWNER(x) (((x) >> LW_LOCK_OWNER_SHIFT) & LW_LOCK_OWNER_MASK)

class Method;
class Object;
class Thread;

class Monitor {
 public:
  ~Monitor();

  static bool IsSensitiveThread();
  static void Init(uint32_t lock_profiling_threshold, bool (*is_sensitive_thread_hook)());

  static uint32_t GetThinLockId(uint32_t raw_lock_word);

  static void MonitorEnter(Thread* thread, Object* obj);
  static bool MonitorExit(Thread* thread, Object* obj);

  static void Notify(Thread* self, Object* obj);
  static void NotifyAll(Thread* self, Object* obj);
  static void Wait(Thread* self, Object* obj, int64_t ms, int32_t ns, bool interruptShouldThrow);

  static void DescribeWait(std::ostream& os, const Thread* thread);

  Object* GetObject();

 private:
  explicit Monitor(Object* obj);

  void AppendToWaitSet(Thread* thread);
  void RemoveFromWaitSet(Thread* thread);

  static void Inflate(Thread* self, Object* obj);

  void LogContentionEvent(Thread* self, uint32_t wait_ms, uint32_t sample_percent, const char* owner_filename, uint32_t owner_line_number);

  static void FailedUnlock(Object* obj, Thread* expected_owner, Thread* found_owner, Monitor* mon);

  void Lock(Thread* self);
  bool Unlock(Thread* thread);

  void Notify(Thread* self);
  void NotifyAll(Thread* self);

  void Wait(Thread* self, int64_t msec, int32_t nsec, bool interruptShouldThrow);

  // Translates the provided method and pc into its declaring class' source file and line number.
  void TranslateLocation(const Method* method, uint32_t pc,
                         const char*& source_file, uint32_t& line_number) const;

  static bool (*is_sensitive_thread_hook_)();
  static uint32_t lock_profiling_threshold_;

  // Which thread currently owns the lock?
  Thread* volatile owner_;

  // Owner's recursive lock depth.
  int lock_count_;

  // What object are we part of (for debugging).
  Object* const obj_;

  // Threads currently waiting on this monitor.
  Thread* wait_set_;

  Mutex lock_;

  // Method and pc where the lock owner acquired the lock, used when lock
  // sampling is enabled. locking_method_ may be null if the lock is currently
  // unlocked, or if the lock is acquired by the system when the stack is empty.
  const Method* locking_method_;
  uintptr_t locking_pc_;

  friend class MonitorList;
  friend class Object;
  DISALLOW_COPY_AND_ASSIGN(Monitor);
};

class MonitorList {
 public:
  MonitorList();
  ~MonitorList();

  void Add(Monitor* m);

  void SweepMonitorList(Heap::IsMarkedTester is_marked, void* arg);

 private:
  Mutex lock_;
  std::list<Monitor*> list_;

  DISALLOW_COPY_AND_ASSIGN(MonitorList);
};

}  // namespace art

#endif  // ART_SRC_MONITOR_H_