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/allocator.h"
29#include "base/mutex.h"
30#include "gc_root.h"
31#include "object_callbacks.h"
32#include "read_barrier_option.h"
33#include "thread_state.h"
34
35namespace art {
36
37class LockWord;
38template<class T> class Handle;
39class Thread;
40class StackVisitor;
41typedef uint32_t MonitorId;
42
43namespace mirror {
44  class ArtMethod;
45  class Object;
46}  // namespace mirror
47
48class Monitor {
49 public:
50  // The default number of spins that are done before thread suspension is used to forcibly inflate
51  // a lock word. See Runtime::max_spins_before_thin_lock_inflation_.
52  constexpr static size_t kDefaultMaxSpinsBeforeThinLockInflation = 50;
53
54  ~Monitor();
55
56  static bool IsSensitiveThread();
57  static void Init(uint32_t lock_profiling_threshold, bool (*is_sensitive_thread_hook)());
58
59  // Return the thread id of the lock owner or 0 when there is no owner.
60  static uint32_t GetLockOwnerThreadId(mirror::Object* obj)
61      NO_THREAD_SAFETY_ANALYSIS;  // TODO: Reading lock owner without holding lock is racy.
62
63  static mirror::Object* MonitorEnter(Thread* thread, mirror::Object* obj)
64      EXCLUSIVE_LOCK_FUNCTION(obj)
65      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
66  static bool MonitorExit(Thread* thread, mirror::Object* obj)
67      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
68      UNLOCK_FUNCTION(obj);
69
70  static void Notify(Thread* self, mirror::Object* obj)
71      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
72    DoNotify(self, obj, false);
73  }
74  static void NotifyAll(Thread* self, mirror::Object* obj)
75      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
76    DoNotify(self, obj, true);
77  }
78  static void Wait(Thread* self, mirror::Object* obj, int64_t ms, int32_t ns,
79                   bool interruptShouldThrow, ThreadState why)
80      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
81
82  static void DescribeWait(std::ostream& os, const Thread* thread)
83      LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_)
84      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
85
86  // Used to implement JDWP's ThreadReference.CurrentContendedMonitor.
87  static mirror::Object* GetContendedMonitor(Thread* thread)
88      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
89
90  // Calls 'callback' once for each lock held in the single stack frame represented by
91  // the current state of 'stack_visitor'.
92  // The abort_on_failure flag allows to not die when the state of the runtime is unorderly. This
93  // is necessary when we have already aborted but want to dump the stack as much as we can.
94  static void VisitLocks(StackVisitor* stack_visitor, void (*callback)(mirror::Object*, void*),
95                         void* callback_context, bool abort_on_failure = true)
96      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
97
98  static bool IsValidLockWord(LockWord lock_word);
99
100  template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
101  mirror::Object* GetObject() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
102    return obj_.Read<kReadBarrierOption>();
103  }
104
105  void SetObject(mirror::Object* object);
106
107  Thread* GetOwner() const NO_THREAD_SAFETY_ANALYSIS {
108    return owner_;
109  }
110
111  int32_t GetHashCode();
112
113  bool IsLocked() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
114
115  bool HasHashCode() const {
116    return hash_code_.LoadRelaxed() != 0;
117  }
118
119  MonitorId GetMonitorId() const {
120    return monitor_id_;
121  }
122
123  // Inflate the lock on obj. May fail to inflate for spurious reasons, always re-check.
124  static void InflateThinLocked(Thread* self, Handle<mirror::Object> obj, LockWord lock_word,
125                                uint32_t hash_code) NO_THREAD_SAFETY_ANALYSIS;
126
127  static bool Deflate(Thread* self, mirror::Object* obj)
128      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
129
130 private:
131  explicit Monitor(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code)
132        SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
133  explicit Monitor(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code,
134                   MonitorId id) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
135
136  // Install the monitor into its object, may fail if another thread installs a different monitor
137  // first.
138  bool Install(Thread* self)
139      LOCKS_EXCLUDED(monitor_lock_)
140      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
141
142  void AppendToWaitSet(Thread* thread) EXCLUSIVE_LOCKS_REQUIRED(monitor_lock_);
143  void RemoveFromWaitSet(Thread* thread) EXCLUSIVE_LOCKS_REQUIRED(monitor_lock_);
144
145  /*
146   * Changes the shape of a monitor from thin to fat, preserving the internal lock state. The
147   * calling thread must own the lock or the owner must be suspended. There's a race with other
148   * threads inflating the lock, installing hash codes and spurious failures. The caller should
149   * re-read the lock word following the call.
150   */
151  static void Inflate(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code)
152      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
153
154  void LogContentionEvent(Thread* self, uint32_t wait_ms, uint32_t sample_percent,
155                          const char* owner_filename, uint32_t owner_line_number)
156      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
157
158  static void FailedUnlock(mirror::Object* obj, Thread* expected_owner, Thread* found_owner, Monitor* mon)
159      LOCKS_EXCLUDED(Locks::thread_list_lock_)
160      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
161
162  void Lock(Thread* self)
163      LOCKS_EXCLUDED(monitor_lock_)
164      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
165  bool Unlock(Thread* thread)
166      LOCKS_EXCLUDED(monitor_lock_)
167      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
168
169  static void DoNotify(Thread* self, mirror::Object* obj, bool notify_all)
170      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
171
172  void Notify(Thread* self)
173      LOCKS_EXCLUDED(monitor_lock_)
174      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
175
176  void NotifyAll(Thread* self)
177      LOCKS_EXCLUDED(monitor_lock_)
178      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
179
180
181  void Wait(Thread* self, int64_t msec, int32_t nsec, bool interruptShouldThrow, ThreadState why)
182      LOCKS_EXCLUDED(monitor_lock_)
183      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
184
185  // Translates the provided method and pc into its declaring class' source file and line number.
186  void TranslateLocation(mirror::ArtMethod* method, uint32_t pc,
187                         const char** source_file, uint32_t* line_number) const
188      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
189
190  uint32_t GetOwnerThreadId();
191
192  static bool (*is_sensitive_thread_hook_)();
193  static uint32_t lock_profiling_threshold_;
194
195  Mutex monitor_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
196
197  ConditionVariable monitor_contenders_ GUARDED_BY(monitor_lock_);
198
199  // Number of people waiting on the condition.
200  size_t num_waiters_ GUARDED_BY(monitor_lock_);
201
202  // Which thread currently owns the lock?
203  Thread* volatile owner_ GUARDED_BY(monitor_lock_);
204
205  // Owner's recursive lock depth.
206  int lock_count_ GUARDED_BY(monitor_lock_);
207
208  // What object are we part of. This is a weak root. Do not access
209  // this directly, use GetObject() to read it so it will be guarded
210  // by a read barrier.
211  GcRoot<mirror::Object> obj_;
212
213  // Threads currently waiting on this monitor.
214  Thread* wait_set_ GUARDED_BY(monitor_lock_);
215
216  // Stored object hash code, generated lazily by GetHashCode.
217  AtomicInteger hash_code_;
218
219  // Method and dex pc where the lock owner acquired the lock, used when lock
220  // sampling is enabled. locking_method_ may be null if the lock is currently
221  // unlocked, or if the lock is acquired by the system when the stack is empty.
222  mirror::ArtMethod* locking_method_ GUARDED_BY(monitor_lock_);
223  uint32_t locking_dex_pc_ GUARDED_BY(monitor_lock_);
224
225  // The denser encoded version of this monitor as stored in the lock word.
226  MonitorId monitor_id_;
227
228#ifdef __LP64__
229  // Free list for monitor pool.
230  Monitor* next_free_ GUARDED_BY(Locks::allocated_monitor_ids_lock_);
231#endif
232
233  friend class MonitorInfo;
234  friend class MonitorList;
235  friend class MonitorPool;
236  friend class mirror::Object;
237  DISALLOW_COPY_AND_ASSIGN(Monitor);
238};
239
240class MonitorList {
241 public:
242  MonitorList();
243  ~MonitorList();
244
245  void Add(Monitor* m);
246
247  void SweepMonitorList(IsMarkedCallback* callback, void* arg)
248      LOCKS_EXCLUDED(monitor_list_lock_) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
249  void DisallowNewMonitors() LOCKS_EXCLUDED(monitor_list_lock_);
250  void AllowNewMonitors() LOCKS_EXCLUDED(monitor_list_lock_);
251  // Returns how many monitors were deflated.
252  size_t DeflateMonitors() LOCKS_EXCLUDED(monitor_list_lock_)
253      EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_);
254
255  typedef std::list<Monitor*, TrackingAllocator<Monitor*, kAllocatorTagMonitorList>> Monitors;
256
257 private:
258  // During sweeping we may free an object and on a separate thread have an object created using
259  // the newly freed memory. That object may then have its lock-word inflated and a monitor created.
260  // If we allow new monitor registration during sweeping this monitor may be incorrectly freed as
261  // the object wasn't marked when sweeping began.
262  bool allow_new_monitors_ GUARDED_BY(monitor_list_lock_);
263  Mutex monitor_list_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
264  ConditionVariable monitor_add_condition_ GUARDED_BY(monitor_list_lock_);
265  Monitors list_ GUARDED_BY(monitor_list_lock_);
266
267  friend class Monitor;
268  DISALLOW_COPY_AND_ASSIGN(MonitorList);
269};
270
271// Collects information about the current state of an object's monitor.
272// This is very unsafe, and must only be called when all threads are suspended.
273// For use only by the JDWP implementation.
274class MonitorInfo {
275 public:
276  explicit MonitorInfo(mirror::Object* o) EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_);
277
278  Thread* owner_;
279  size_t entry_count_;
280  std::vector<Thread*> waiters_;
281
282 private:
283  DISALLOW_COPY_AND_ASSIGN(MonitorInfo);
284};
285
286}  // namespace art
287
288#endif  // ART_RUNTIME_MONITOR_H_
289