monitor.h revision ffddfdf6fec0b9d98a692e27242eecb15af5ead2 
1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ART_RUNTIME_MONITOR_H_
18#define ART_RUNTIME_MONITOR_H_
19
20#include <pthread.h>
21#include <stdint.h>
22
23#include <iosfwd>
24#include <list>
25#include <vector>
26
27#include "atomic.h"
28#include "base/mutex.h"
29#include "object_callbacks.h"
30#include "read_barrier.h"
31#include "thread_state.h"
32
33namespace art {
34
35class LockWord;
36template<class T> class Handle;
37class Thread;
38class StackVisitor;
39typedef uint32_t MonitorId;
40
41namespace mirror {
42  class ArtMethod;
43  class Object;
44}  // namespace mirror
45
46class Monitor {
47 public:
48  // The default number of spins that are done before thread suspension is used to forcibly inflate
49  // a lock word. See Runtime::max_spins_before_thin_lock_inflation_.
50  constexpr static size_t kDefaultMaxSpinsBeforeThinLockInflation = 50;
51
52  ~Monitor();
53
54  static bool IsSensitiveThread();
55  static void Init(uint32_t lock_profiling_threshold, bool (*is_sensitive_thread_hook)());
56
57  // Return the thread id of the lock owner or 0 when there is no owner.
58  static uint32_t GetLockOwnerThreadId(mirror::Object* obj)
59      NO_THREAD_SAFETY_ANALYSIS;  // TODO: Reading lock owner without holding lock is racy.
60
61  static mirror::Object* MonitorEnter(Thread* thread, mirror::Object* obj)
62      EXCLUSIVE_LOCK_FUNCTION(obj)
63      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
64  static bool MonitorExit(Thread* thread, mirror::Object* obj)
65      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
66      UNLOCK_FUNCTION(obj);
67
68  static void Notify(Thread* self, mirror::Object* obj)
69      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
70    DoNotify(self, obj, false);
71  }
72  static void NotifyAll(Thread* self, mirror::Object* obj)
73      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
74    DoNotify(self, obj, true);
75  }
76  static void Wait(Thread* self, mirror::Object* obj, int64_t ms, int32_t ns,
77                   bool interruptShouldThrow, ThreadState why)
78      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
79
80  static void DescribeWait(std::ostream& os, const Thread* thread)
81      LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_)
82      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
83
84  // Used to implement JDWP's ThreadReference.CurrentContendedMonitor.
85  static mirror::Object* GetContendedMonitor(Thread* thread)
86      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
87
88  // Calls 'callback' once for each lock held in the single stack frame represented by
89  // the current state of 'stack_visitor'.
90  static void VisitLocks(StackVisitor* stack_visitor, void (*callback)(mirror::Object*, void*),
91                         void* callback_context)
92      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
93
94  static bool IsValidLockWord(LockWord lock_word);
95
96  template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
97  mirror::Object* GetObject() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
98    return ReadBarrier::BarrierForWeakRoot<mirror::Object, kReadBarrierOption>(&obj_);
99  }
100
101  void SetObject(mirror::Object* object);
102
103  Thread* GetOwner() const NO_THREAD_SAFETY_ANALYSIS {
104    return owner_;
105  }
106
107  int32_t GetHashCode();
108
109  bool IsLocked() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
110
111  bool HasHashCode() const {
112    return hash_code_.LoadRelaxed() != 0;
113  }
114
115  MonitorId GetMonitorId() const {
116    return monitor_id_;
117  }
118
119  static void InflateThinLocked(Thread* self, Handle<mirror::Object> obj, LockWord lock_word,
120                                uint32_t hash_code) NO_THREAD_SAFETY_ANALYSIS;
121
122  static bool Deflate(Thread* self, mirror::Object* obj)
123      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
124
125 private:
126  explicit Monitor(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code)
127      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
128
129  // Install the monitor into its object, may fail if another thread installs a different monitor
130  // first.
131  bool Install(Thread* self)
132      LOCKS_EXCLUDED(monitor_lock_)
133      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
134
135  void AppendToWaitSet(Thread* thread) EXCLUSIVE_LOCKS_REQUIRED(monitor_lock_);
136  void RemoveFromWaitSet(Thread* thread) EXCLUSIVE_LOCKS_REQUIRED(monitor_lock_);
137
138  static void Inflate(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code)
139      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
140
141  void LogContentionEvent(Thread* self, uint32_t wait_ms, uint32_t sample_percent,
142                          const char* owner_filename, uint32_t owner_line_number)
143      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
144
145  static void FailedUnlock(mirror::Object* obj, Thread* expected_owner, Thread* found_owner, Monitor* mon)
146      LOCKS_EXCLUDED(Locks::thread_list_lock_)
147      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
148
149  void Lock(Thread* self)
150      LOCKS_EXCLUDED(monitor_lock_)
151      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
152  bool Unlock(Thread* thread)
153      LOCKS_EXCLUDED(monitor_lock_)
154      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
155
156  static void DoNotify(Thread* self, mirror::Object* obj, bool notify_all)
157      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
158
159  void Notify(Thread* self)
160      LOCKS_EXCLUDED(monitor_lock_)
161      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
162
163  void NotifyAll(Thread* self)
164      LOCKS_EXCLUDED(monitor_lock_)
165      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
166
167
168  void Wait(Thread* self, int64_t msec, int32_t nsec, bool interruptShouldThrow, ThreadState why)
169      LOCKS_EXCLUDED(monitor_lock_)
170      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
171
172  // Translates the provided method and pc into its declaring class' source file and line number.
173  void TranslateLocation(mirror::ArtMethod* method, uint32_t pc,
174                         const char** source_file, uint32_t* line_number) const
175      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
176
177  uint32_t GetOwnerThreadId();
178
179  static bool (*is_sensitive_thread_hook_)();
180  static uint32_t lock_profiling_threshold_;
181
182  Mutex monitor_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
183
184  ConditionVariable monitor_contenders_ GUARDED_BY(monitor_lock_);
185
186  // Number of people waiting on the condition.
187  size_t num_waiters_ GUARDED_BY(monitor_lock_);
188
189  // Which thread currently owns the lock?
190  Thread* volatile owner_ GUARDED_BY(monitor_lock_);
191
192  // Owner's recursive lock depth.
193  int lock_count_ GUARDED_BY(monitor_lock_);
194
195  // What object are we part of. This is a weak root. Do not access
196  // this directly, use GetObject() to read it so it will be guarded
197  // by a read barrier.
198  mirror::Object* obj_;
199
200  // Threads currently waiting on this monitor.
201  Thread* wait_set_ GUARDED_BY(monitor_lock_);
202
203  // Stored object hash code, generated lazily by GetHashCode.
204  AtomicInteger hash_code_;
205
206  // Method and dex pc where the lock owner acquired the lock, used when lock
207  // sampling is enabled. locking_method_ may be null if the lock is currently
208  // unlocked, or if the lock is acquired by the system when the stack is empty.
209  mirror::ArtMethod* locking_method_ GUARDED_BY(monitor_lock_);
210  uint32_t locking_dex_pc_ GUARDED_BY(monitor_lock_);
211
212  // The denser encoded version of this monitor as stored in the lock word.
213  MonitorId monitor_id_;
214
215  friend class MonitorInfo;
216  friend class MonitorList;
217  friend class mirror::Object;
218  DISALLOW_COPY_AND_ASSIGN(Monitor);
219};
220
221class MonitorList {
222 public:
223  MonitorList();
224  ~MonitorList();
225
226  void Add(Monitor* m);
227
228  void SweepMonitorList(IsMarkedCallback* callback, void* arg)
229      LOCKS_EXCLUDED(monitor_list_lock_) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
230  void DisallowNewMonitors() LOCKS_EXCLUDED(monitor_list_lock_);
231  void AllowNewMonitors() LOCKS_EXCLUDED(monitor_list_lock_);
232  void DeflateMonitors() LOCKS_EXCLUDED(monitor_list_lock_)
233      EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_);
234
235 private:
236  // During sweeping we may free an object and on a separate thread have an object created using
237  // the newly freed memory. That object may then have its lock-word inflated and a monitor created.
238  // If we allow new monitor registration during sweeping this monitor may be incorrectly freed as
239  // the object wasn't marked when sweeping began.
240  bool allow_new_monitors_ GUARDED_BY(monitor_list_lock_);
241  Mutex monitor_list_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
242  ConditionVariable monitor_add_condition_ GUARDED_BY(monitor_list_lock_);
243  std::list<Monitor*> list_ GUARDED_BY(monitor_list_lock_);
244
245  friend class Monitor;
246  DISALLOW_COPY_AND_ASSIGN(MonitorList);
247};
248
249// Collects information about the current state of an object's monitor.
250// This is very unsafe, and must only be called when all threads are suspended.
251// For use only by the JDWP implementation.
252class MonitorInfo {
253 public:
254  explicit MonitorInfo(mirror::Object* o) EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_);
255
256  Thread* owner_;
257  size_t entry_count_;
258  std::vector<Thread*> waiters_;
259
260 private:
261  DISALLOW_COPY_AND_ASSIGN(MonitorInfo);
262};
263
264}  // namespace art
265
266#endif  // ART_RUNTIME_MONITOR_H_
267