2 * Copyright (C) 2008 The Android Open Source Project
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
17 #ifndef ART_RUNTIME_MONITOR_H_
18 #define ART_RUNTIME_MONITOR_H_
29 #include "base/allocator.h"
30 #include "base/mutex.h"
32 #include "lock_word.h"
33 #include "object_callbacks.h"
34 #include "read_barrier_option.h"
35 #include "thread_state.h"
41 template<class T> class Handle;
44 typedef uint32_t MonitorId;
52 // The default number of spins that are done before thread suspension is used to forcibly inflate
53 // a lock word. See Runtime::max_spins_before_thin_lock_inflation_.
54 constexpr static size_t kDefaultMaxSpinsBeforeThinLockInflation = 50;
58 static void Init(uint32_t lock_profiling_threshold);
60 // Return the thread id of the lock owner or 0 when there is no owner.
61 static uint32_t GetLockOwnerThreadId(mirror::Object* obj)
62 NO_THREAD_SAFETY_ANALYSIS; // TODO: Reading lock owner without holding lock is racy.
64 // NO_THREAD_SAFETY_ANALYSIS for mon->Lock.
65 static mirror::Object* MonitorEnter(Thread* thread, mirror::Object* obj)
66 EXCLUSIVE_LOCK_FUNCTION(obj)
67 NO_THREAD_SAFETY_ANALYSIS
68 REQUIRES(!Roles::uninterruptible_)
69 SHARED_REQUIRES(Locks::mutator_lock_);
71 // NO_THREAD_SAFETY_ANALYSIS for mon->Unlock.
72 static bool MonitorExit(Thread* thread, mirror::Object* obj)
73 NO_THREAD_SAFETY_ANALYSIS
74 REQUIRES(!Roles::uninterruptible_)
75 SHARED_REQUIRES(Locks::mutator_lock_)
78 static void Notify(Thread* self, mirror::Object* obj) SHARED_REQUIRES(Locks::mutator_lock_) {
79 DoNotify(self, obj, false);
81 static void NotifyAll(Thread* self, mirror::Object* obj) SHARED_REQUIRES(Locks::mutator_lock_) {
82 DoNotify(self, obj, true);
85 // Object.wait(). Also called for class init.
86 // NO_THREAD_SAFETY_ANALYSIS for mon->Wait.
87 static void Wait(Thread* self, mirror::Object* obj, int64_t ms, int32_t ns,
88 bool interruptShouldThrow, ThreadState why)
89 SHARED_REQUIRES(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS;
91 static void DescribeWait(std::ostream& os, const Thread* thread)
92 REQUIRES(!Locks::thread_suspend_count_lock_)
93 SHARED_REQUIRES(Locks::mutator_lock_);
95 // Used to implement JDWP's ThreadReference.CurrentContendedMonitor.
96 static mirror::Object* GetContendedMonitor(Thread* thread)
97 SHARED_REQUIRES(Locks::mutator_lock_);
99 // Calls 'callback' once for each lock held in the single stack frame represented by
100 // the current state of 'stack_visitor'.
101 // The abort_on_failure flag allows to not die when the state of the runtime is unorderly. This
102 // is necessary when we have already aborted but want to dump the stack as much as we can.
103 static void VisitLocks(StackVisitor* stack_visitor, void (*callback)(mirror::Object*, void*),
104 void* callback_context, bool abort_on_failure = true)
105 SHARED_REQUIRES(Locks::mutator_lock_);
107 static bool IsValidLockWord(LockWord lock_word);
109 template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
110 mirror::Object* GetObject() SHARED_REQUIRES(Locks::mutator_lock_) {
111 return obj_.Read<kReadBarrierOption>();
114 void SetObject(mirror::Object* object);
116 Thread* GetOwner() const NO_THREAD_SAFETY_ANALYSIS {
120 int32_t GetHashCode();
122 bool IsLocked() SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!monitor_lock_);
124 bool HasHashCode() const {
125 return hash_code_.LoadRelaxed() != 0;
128 MonitorId GetMonitorId() const {
132 // Inflate the lock on obj. May fail to inflate for spurious reasons, always re-check.
133 static void InflateThinLocked(Thread* self, Handle<mirror::Object> obj, LockWord lock_word,
134 uint32_t hash_code) SHARED_REQUIRES(Locks::mutator_lock_);
136 // Not exclusive because ImageWriter calls this during a Heap::VisitObjects() that
137 // does not allow a thread suspension in the middle. TODO: maybe make this exclusive.
138 // NO_THREAD_SAFETY_ANALYSIS for monitor->monitor_lock_.
139 static bool Deflate(Thread* self, mirror::Object* obj)
140 SHARED_REQUIRES(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS;
143 void* operator new(size_t size) {
144 // Align Monitor* as per the monitor ID field size in the lock word.
146 int error = posix_memalign(&result, LockWord::kMonitorIdAlignment, size);
147 CHECK_EQ(error, 0) << strerror(error);
151 void operator delete(void* ptr) {
157 Monitor(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code)
158 SHARED_REQUIRES(Locks::mutator_lock_);
159 Monitor(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code, MonitorId id)
160 SHARED_REQUIRES(Locks::mutator_lock_);
162 // Install the monitor into its object, may fail if another thread installs a different monitor
164 bool Install(Thread* self)
165 REQUIRES(!monitor_lock_)
166 SHARED_REQUIRES(Locks::mutator_lock_);
168 // Links a thread into a monitor's wait set. The monitor lock must be held by the caller of this
170 void AppendToWaitSet(Thread* thread) REQUIRES(monitor_lock_);
172 // Unlinks a thread from a monitor's wait set. The monitor lock must be held by the caller of
174 void RemoveFromWaitSet(Thread* thread) REQUIRES(monitor_lock_);
176 // Changes the shape of a monitor from thin to fat, preserving the internal lock state. The
177 // calling thread must own the lock or the owner must be suspended. There's a race with other
178 // threads inflating the lock, installing hash codes and spurious failures. The caller should
179 // re-read the lock word following the call.
180 static void Inflate(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code)
181 SHARED_REQUIRES(Locks::mutator_lock_)
182 NO_THREAD_SAFETY_ANALYSIS; // For m->Install(self)
184 void LogContentionEvent(Thread* self, uint32_t wait_ms, uint32_t sample_percent,
185 const char* owner_filename, int32_t owner_line_number)
186 SHARED_REQUIRES(Locks::mutator_lock_);
188 static void FailedUnlock(mirror::Object* obj,
189 uint32_t expected_owner_thread_id,
190 uint32_t found_owner_thread_id,
192 REQUIRES(!Locks::thread_list_lock_,
194 SHARED_REQUIRES(Locks::mutator_lock_);
196 void Lock(Thread* self)
197 REQUIRES(!monitor_lock_)
198 SHARED_REQUIRES(Locks::mutator_lock_);
199 bool Unlock(Thread* thread)
200 REQUIRES(!monitor_lock_)
201 SHARED_REQUIRES(Locks::mutator_lock_);
203 static void DoNotify(Thread* self, mirror::Object* obj, bool notify_all)
204 SHARED_REQUIRES(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS; // For mon->Notify.
206 void Notify(Thread* self)
207 REQUIRES(!monitor_lock_)
208 SHARED_REQUIRES(Locks::mutator_lock_);
210 void NotifyAll(Thread* self)
211 REQUIRES(!monitor_lock_)
212 SHARED_REQUIRES(Locks::mutator_lock_);
214 static std::string PrettyContentionInfo(const std::string& owner_name,
216 ArtMethod* owners_method,
217 uint32_t owners_dex_pc,
219 REQUIRES(!Locks::thread_list_lock_)
220 SHARED_REQUIRES(Locks::mutator_lock_);
222 // Wait on a monitor until timeout, interrupt, or notification. Used for Object.wait() and
223 // (somewhat indirectly) Thread.sleep() and Thread.join().
225 // If another thread calls Thread.interrupt(), we throw InterruptedException and return
226 // immediately if one of the following are true:
227 // - blocked in wait(), wait(long), or wait(long, int) methods of Object
228 // - blocked in join(), join(long), or join(long, int) methods of Thread
229 // - blocked in sleep(long), or sleep(long, int) methods of Thread
230 // Otherwise, we set the "interrupted" flag.
232 // Checks to make sure that "ns" is in the range 0-999999 (i.e. fractions of a millisecond) and
233 // throws the appropriate exception if it isn't.
235 // The spec allows "spurious wakeups", and recommends that all code using Object.wait() do so in
236 // a loop. This appears to derive from concerns about pthread_cond_wait() on multiprocessor
237 // systems. Some commentary on the web casts doubt on whether these can/should occur.
239 // Since we're allowed to wake up "early", we clamp extremely long durations to return at the end
240 // of the 32-bit time epoch.
241 void Wait(Thread* self, int64_t msec, int32_t nsec, bool interruptShouldThrow, ThreadState why)
242 REQUIRES(!monitor_lock_)
243 SHARED_REQUIRES(Locks::mutator_lock_);
245 // Translates the provided method and pc into its declaring class' source file and line number.
246 static void TranslateLocation(ArtMethod* method, uint32_t pc,
247 const char** source_file,
248 int32_t* line_number)
249 SHARED_REQUIRES(Locks::mutator_lock_);
251 uint32_t GetOwnerThreadId() REQUIRES(!monitor_lock_);
253 // Support for systrace output of monitor operations.
254 ALWAYS_INLINE static void AtraceMonitorLock(Thread* self,
257 SHARED_REQUIRES(Locks::mutator_lock_);
258 static void AtraceMonitorLockImpl(Thread* self,
261 SHARED_REQUIRES(Locks::mutator_lock_);
262 ALWAYS_INLINE static void AtraceMonitorUnlock();
264 static uint32_t lock_profiling_threshold_;
266 Mutex monitor_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
268 ConditionVariable monitor_contenders_ GUARDED_BY(monitor_lock_);
270 // Number of people waiting on the condition.
271 size_t num_waiters_ GUARDED_BY(monitor_lock_);
273 // Which thread currently owns the lock?
274 Thread* volatile owner_ GUARDED_BY(monitor_lock_);
276 // Owner's recursive lock depth.
277 int lock_count_ GUARDED_BY(monitor_lock_);
279 // What object are we part of. This is a weak root. Do not access
280 // this directly, use GetObject() to read it so it will be guarded
281 // by a read barrier.
282 GcRoot<mirror::Object> obj_;
284 // Threads currently waiting on this monitor.
285 Thread* wait_set_ GUARDED_BY(monitor_lock_);
287 // Stored object hash code, generated lazily by GetHashCode.
288 AtomicInteger hash_code_;
290 // Method and dex pc where the lock owner acquired the lock, used when lock
291 // sampling is enabled. locking_method_ may be null if the lock is currently
292 // unlocked, or if the lock is acquired by the system when the stack is empty.
293 ArtMethod* locking_method_ GUARDED_BY(monitor_lock_);
294 uint32_t locking_dex_pc_ GUARDED_BY(monitor_lock_);
296 // The denser encoded version of this monitor as stored in the lock word.
297 MonitorId monitor_id_;
300 // Free list for monitor pool.
301 Monitor* next_free_ GUARDED_BY(Locks::allocated_monitor_ids_lock_);
304 friend class MonitorInfo;
305 friend class MonitorList;
306 friend class MonitorPool;
307 friend class mirror::Object;
308 DISALLOW_COPY_AND_ASSIGN(Monitor);
316 void Add(Monitor* m) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!monitor_list_lock_);
318 void SweepMonitorList(IsMarkedVisitor* visitor)
319 REQUIRES(!monitor_list_lock_) SHARED_REQUIRES(Locks::mutator_lock_);
320 void DisallowNewMonitors() REQUIRES(!monitor_list_lock_);
321 void AllowNewMonitors() REQUIRES(!monitor_list_lock_);
322 void BroadcastForNewMonitors() REQUIRES(!monitor_list_lock_);
323 // Returns how many monitors were deflated.
324 size_t DeflateMonitors() REQUIRES(!monitor_list_lock_) REQUIRES(Locks::mutator_lock_);
326 typedef std::list<Monitor*, TrackingAllocator<Monitor*, kAllocatorTagMonitorList>> Monitors;
329 // During sweeping we may free an object and on a separate thread have an object created using
330 // the newly freed memory. That object may then have its lock-word inflated and a monitor created.
331 // If we allow new monitor registration during sweeping this monitor may be incorrectly freed as
332 // the object wasn't marked when sweeping began.
333 bool allow_new_monitors_ GUARDED_BY(monitor_list_lock_);
334 Mutex monitor_list_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
335 ConditionVariable monitor_add_condition_ GUARDED_BY(monitor_list_lock_);
336 Monitors list_ GUARDED_BY(monitor_list_lock_);
338 friend class Monitor;
339 DISALLOW_COPY_AND_ASSIGN(MonitorList);
342 // Collects information about the current state of an object's monitor.
343 // This is very unsafe, and must only be called when all threads are suspended.
344 // For use only by the JDWP implementation.
347 MonitorInfo() = default;
348 MonitorInfo(const MonitorInfo&) = default;
349 MonitorInfo& operator=(const MonitorInfo&) = default;
350 explicit MonitorInfo(mirror::Object* o) REQUIRES(Locks::mutator_lock_);
354 std::vector<Thread*> waiters_;
359 #endif // ART_RUNTIME_MONITOR_H_