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 #include <stdlib.h> 23 24 #include <iosfwd> 25 #include <list> 26 #include <vector> 27 28 #include "base/allocator.h" 29 #include "base/atomic.h" 30 #include "base/mutex.h" 31 #include "gc_root.h" 32 #include "lock_word.h" 33 #include "obj_ptr.h" 34 #include "read_barrier_option.h" 35 #include "runtime_callbacks.h" 36 #include "thread_state.h" 37 38 namespace art { 39 40 class ArtMethod; 41 class IsMarkedVisitor; 42 class LockWord; 43 template<class T> class Handle; 44 class StackVisitor; 45 class Thread; 46 typedef uint32_t MonitorId; 47 48 namespace mirror { 49 class Object; 50 } // namespace mirror 51 52 enum class LockReason { 53 kForWait, 54 kForLock, 55 }; 56 57 class Monitor { 58 public: 59 // The default number of spins that are done before thread suspension is used to forcibly inflate 60 // a lock word. See Runtime::max_spins_before_thin_lock_inflation_. 61 constexpr static size_t kDefaultMaxSpinsBeforeThinLockInflation = 50; 62 63 ~Monitor(); 64 65 static void Init(uint32_t lock_profiling_threshold, uint32_t stack_dump_lock_profiling_threshold); 66 67 // Return the thread id of the lock owner or 0 when there is no owner. 68 static uint32_t GetLockOwnerThreadId(ObjPtr<mirror::Object> obj) 69 NO_THREAD_SAFETY_ANALYSIS; // TODO: Reading lock owner without holding lock is racy. 70 71 // NO_THREAD_SAFETY_ANALYSIS for mon->Lock. 72 static ObjPtr<mirror::Object> MonitorEnter(Thread* thread, 73 ObjPtr<mirror::Object> obj, 74 bool trylock) 75 EXCLUSIVE_LOCK_FUNCTION(obj.Ptr()) 76 NO_THREAD_SAFETY_ANALYSIS 77 REQUIRES(!Roles::uninterruptible_) 78 REQUIRES_SHARED(Locks::mutator_lock_); 79 80 // NO_THREAD_SAFETY_ANALYSIS for mon->Unlock. 81 static bool MonitorExit(Thread* thread, ObjPtr<mirror::Object> obj) 82 NO_THREAD_SAFETY_ANALYSIS 83 REQUIRES(!Roles::uninterruptible_) 84 REQUIRES_SHARED(Locks::mutator_lock_) 85 UNLOCK_FUNCTION(obj.Ptr()); 86 Notify(Thread * self,ObjPtr<mirror::Object> obj)87 static void Notify(Thread* self, ObjPtr<mirror::Object> obj) 88 REQUIRES_SHARED(Locks::mutator_lock_) { 89 DoNotify(self, obj, false); 90 } NotifyAll(Thread * self,ObjPtr<mirror::Object> obj)91 static void NotifyAll(Thread* self, ObjPtr<mirror::Object> obj) 92 REQUIRES_SHARED(Locks::mutator_lock_) { 93 DoNotify(self, obj, true); 94 } 95 96 // Object.wait(). Also called for class init. 97 // NO_THREAD_SAFETY_ANALYSIS for mon->Wait. 98 static void Wait(Thread* self, 99 ObjPtr<mirror::Object> obj, 100 int64_t ms, 101 int32_t ns, 102 bool interruptShouldThrow, ThreadState why) 103 REQUIRES_SHARED(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS; 104 105 static ThreadState FetchState(const Thread* thread, 106 /* out */ ObjPtr<mirror::Object>* monitor_object, 107 /* out */ uint32_t* lock_owner_tid) 108 REQUIRES(!Locks::thread_suspend_count_lock_) 109 REQUIRES_SHARED(Locks::mutator_lock_); 110 111 // Used to implement JDWP's ThreadReference.CurrentContendedMonitor. 112 static ObjPtr<mirror::Object> GetContendedMonitor(Thread* thread) 113 REQUIRES_SHARED(Locks::mutator_lock_); 114 115 // Calls 'callback' once for each lock held in the single stack frame represented by 116 // the current state of 'stack_visitor'. 117 // The abort_on_failure flag allows to not die when the state of the runtime is unorderly. This 118 // is necessary when we have already aborted but want to dump the stack as much as we can. 119 static void VisitLocks(StackVisitor* stack_visitor, 120 void (*callback)(ObjPtr<mirror::Object>, void*), 121 void* callback_context, 122 bool abort_on_failure = true) 123 REQUIRES_SHARED(Locks::mutator_lock_); 124 125 static bool IsValidLockWord(LockWord lock_word); 126 127 template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier> 128 ObjPtr<mirror::Object> GetObject() REQUIRES_SHARED(Locks::mutator_lock_); 129 130 void SetObject(ObjPtr<mirror::Object> object); 131 GetOwner()132 Thread* GetOwner() const NO_THREAD_SAFETY_ANALYSIS { 133 return owner_; 134 } 135 136 int32_t GetHashCode(); 137 138 bool IsLocked() REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!monitor_lock_); 139 HasHashCode()140 bool HasHashCode() const { 141 return hash_code_.load(std::memory_order_relaxed) != 0; 142 } 143 GetMonitorId()144 MonitorId GetMonitorId() const { 145 return monitor_id_; 146 } 147 148 // Inflate the lock on obj. May fail to inflate for spurious reasons, always re-check. 149 static void InflateThinLocked(Thread* self, Handle<mirror::Object> obj, LockWord lock_word, 150 uint32_t hash_code) REQUIRES_SHARED(Locks::mutator_lock_); 151 152 // Not exclusive because ImageWriter calls this during a Heap::VisitObjects() that 153 // does not allow a thread suspension in the middle. TODO: maybe make this exclusive. 154 // NO_THREAD_SAFETY_ANALYSIS for monitor->monitor_lock_. 155 static bool Deflate(Thread* self, ObjPtr<mirror::Object> obj) 156 REQUIRES_SHARED(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS; 157 158 #ifndef __LP64__ new(size_t size)159 void* operator new(size_t size) { 160 // Align Monitor* as per the monitor ID field size in the lock word. 161 void* result; 162 int error = posix_memalign(&result, LockWord::kMonitorIdAlignment, size); 163 CHECK_EQ(error, 0) << strerror(error); 164 return result; 165 } 166 delete(void * ptr)167 void operator delete(void* ptr) { 168 free(ptr); 169 } 170 #endif 171 172 private: 173 Monitor(Thread* self, Thread* owner, ObjPtr<mirror::Object> obj, int32_t hash_code) 174 REQUIRES_SHARED(Locks::mutator_lock_); 175 Monitor(Thread* self, Thread* owner, ObjPtr<mirror::Object> obj, int32_t hash_code, MonitorId id) 176 REQUIRES_SHARED(Locks::mutator_lock_); 177 178 // Install the monitor into its object, may fail if another thread installs a different monitor 179 // first. 180 bool Install(Thread* self) 181 REQUIRES(!monitor_lock_) 182 REQUIRES_SHARED(Locks::mutator_lock_); 183 184 // Links a thread into a monitor's wait set. The monitor lock must be held by the caller of this 185 // routine. 186 void AppendToWaitSet(Thread* thread) REQUIRES(monitor_lock_); 187 188 // Unlinks a thread from a monitor's wait set. The monitor lock must be held by the caller of 189 // this routine. 190 void RemoveFromWaitSet(Thread* thread) REQUIRES(monitor_lock_); 191 192 void SignalContendersAndReleaseMonitorLock(Thread* self) RELEASE(monitor_lock_); 193 194 // Changes the shape of a monitor from thin to fat, preserving the internal lock state. The 195 // calling thread must own the lock or the owner must be suspended. There's a race with other 196 // threads inflating the lock, installing hash codes and spurious failures. The caller should 197 // re-read the lock word following the call. 198 static void Inflate(Thread* self, Thread* owner, ObjPtr<mirror::Object> obj, int32_t hash_code) 199 REQUIRES_SHARED(Locks::mutator_lock_) 200 NO_THREAD_SAFETY_ANALYSIS; // For m->Install(self) 201 202 void LogContentionEvent(Thread* self, 203 uint32_t wait_ms, 204 uint32_t sample_percent, 205 ArtMethod* owner_method, 206 uint32_t owner_dex_pc) 207 REQUIRES_SHARED(Locks::mutator_lock_); 208 209 static void FailedUnlock(ObjPtr<mirror::Object> obj, 210 uint32_t expected_owner_thread_id, 211 uint32_t found_owner_thread_id, 212 Monitor* mon) 213 REQUIRES(!Locks::thread_list_lock_, 214 !monitor_lock_) 215 REQUIRES_SHARED(Locks::mutator_lock_); 216 217 // Try to lock without blocking, returns true if we acquired the lock. 218 bool TryLock(Thread* self) 219 REQUIRES(!monitor_lock_) 220 REQUIRES_SHARED(Locks::mutator_lock_); 221 // Variant for already holding the monitor lock. 222 bool TryLockLocked(Thread* self) 223 REQUIRES(monitor_lock_) 224 REQUIRES_SHARED(Locks::mutator_lock_); 225 226 template<LockReason reason = LockReason::kForLock> 227 void Lock(Thread* self) 228 REQUIRES(!monitor_lock_) 229 REQUIRES_SHARED(Locks::mutator_lock_); 230 231 bool Unlock(Thread* thread) 232 REQUIRES(!monitor_lock_) 233 REQUIRES_SHARED(Locks::mutator_lock_); 234 235 static void DoNotify(Thread* self, ObjPtr<mirror::Object> obj, bool notify_all) 236 REQUIRES_SHARED(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS; // For mon->Notify. 237 238 void Notify(Thread* self) 239 REQUIRES(!monitor_lock_) 240 REQUIRES_SHARED(Locks::mutator_lock_); 241 242 void NotifyAll(Thread* self) 243 REQUIRES(!monitor_lock_) 244 REQUIRES_SHARED(Locks::mutator_lock_); 245 246 static std::string PrettyContentionInfo(const std::string& owner_name, 247 pid_t owner_tid, 248 ArtMethod* owners_method, 249 uint32_t owners_dex_pc, 250 size_t num_waiters) 251 REQUIRES_SHARED(Locks::mutator_lock_); 252 253 // Wait on a monitor until timeout, interrupt, or notification. Used for Object.wait() and 254 // (somewhat indirectly) Thread.sleep() and Thread.join(). 255 // 256 // If another thread calls Thread.interrupt(), we throw InterruptedException and return 257 // immediately if one of the following are true: 258 // - blocked in wait(), wait(long), or wait(long, int) methods of Object 259 // - blocked in join(), join(long), or join(long, int) methods of Thread 260 // - blocked in sleep(long), or sleep(long, int) methods of Thread 261 // Otherwise, we set the "interrupted" flag. 262 // 263 // Checks to make sure that "ns" is in the range 0-999999 (i.e. fractions of a millisecond) and 264 // throws the appropriate exception if it isn't. 265 // 266 // The spec allows "spurious wakeups", and recommends that all code using Object.wait() do so in 267 // a loop. This appears to derive from concerns about pthread_cond_wait() on multiprocessor 268 // systems. Some commentary on the web casts doubt on whether these can/should occur. 269 // 270 // Since we're allowed to wake up "early", we clamp extremely long durations to return at the end 271 // of the 32-bit time epoch. 272 void Wait(Thread* self, int64_t msec, int32_t nsec, bool interruptShouldThrow, ThreadState why) 273 REQUIRES(!monitor_lock_) 274 REQUIRES_SHARED(Locks::mutator_lock_); 275 276 // Translates the provided method and pc into its declaring class' source file and line number. 277 static void TranslateLocation(ArtMethod* method, uint32_t pc, 278 const char** source_file, 279 int32_t* line_number) 280 REQUIRES_SHARED(Locks::mutator_lock_); 281 282 uint32_t GetOwnerThreadId() REQUIRES(!monitor_lock_); 283 284 // Support for systrace output of monitor operations. 285 ALWAYS_INLINE static void AtraceMonitorLock(Thread* self, 286 ObjPtr<mirror::Object> obj, 287 bool is_wait) 288 REQUIRES_SHARED(Locks::mutator_lock_); 289 static void AtraceMonitorLockImpl(Thread* self, 290 ObjPtr<mirror::Object> obj, 291 bool is_wait) 292 REQUIRES_SHARED(Locks::mutator_lock_); 293 ALWAYS_INLINE static void AtraceMonitorUnlock(); 294 295 static uint32_t lock_profiling_threshold_; 296 static uint32_t stack_dump_lock_profiling_threshold_; 297 298 Mutex monitor_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER; 299 300 ConditionVariable monitor_contenders_ GUARDED_BY(monitor_lock_); 301 302 // Number of people waiting on the condition. 303 size_t num_waiters_ GUARDED_BY(monitor_lock_); 304 305 // Which thread currently owns the lock? 306 Thread* volatile owner_ GUARDED_BY(monitor_lock_); 307 308 // Owner's recursive lock depth. 309 int lock_count_ GUARDED_BY(monitor_lock_); 310 311 // What object are we part of. This is a weak root. Do not access 312 // this directly, use GetObject() to read it so it will be guarded 313 // by a read barrier. 314 GcRoot<mirror::Object> obj_; 315 316 // Threads currently waiting on this monitor. 317 Thread* wait_set_ GUARDED_BY(monitor_lock_); 318 319 // Threads that were waiting on this monitor, but are now contending on it. 320 Thread* wake_set_ GUARDED_BY(monitor_lock_); 321 322 // Stored object hash code, generated lazily by GetHashCode. 323 AtomicInteger hash_code_; 324 325 // Method and dex pc where the lock owner acquired the lock, used when lock 326 // sampling is enabled. locking_method_ may be null if the lock is currently 327 // unlocked, or if the lock is acquired by the system when the stack is empty. 328 ArtMethod* locking_method_ GUARDED_BY(monitor_lock_); 329 uint32_t locking_dex_pc_ GUARDED_BY(monitor_lock_); 330 331 // The denser encoded version of this monitor as stored in the lock word. 332 MonitorId monitor_id_; 333 334 #ifdef __LP64__ 335 // Free list for monitor pool. 336 Monitor* next_free_ GUARDED_BY(Locks::allocated_monitor_ids_lock_); 337 #endif 338 339 friend class MonitorInfo; 340 friend class MonitorList; 341 friend class MonitorPool; 342 friend class mirror::Object; 343 DISALLOW_COPY_AND_ASSIGN(Monitor); 344 }; 345 346 class MonitorList { 347 public: 348 MonitorList(); 349 ~MonitorList(); 350 351 void Add(Monitor* m) REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!monitor_list_lock_); 352 353 void SweepMonitorList(IsMarkedVisitor* visitor) 354 REQUIRES(!monitor_list_lock_) REQUIRES_SHARED(Locks::mutator_lock_); 355 void DisallowNewMonitors() REQUIRES(!monitor_list_lock_); 356 void AllowNewMonitors() REQUIRES(!monitor_list_lock_); 357 void BroadcastForNewMonitors() REQUIRES(!monitor_list_lock_); 358 // Returns how many monitors were deflated. 359 size_t DeflateMonitors() REQUIRES(!monitor_list_lock_) REQUIRES(Locks::mutator_lock_); 360 size_t Size() REQUIRES(!monitor_list_lock_); 361 362 typedef std::list<Monitor*, TrackingAllocator<Monitor*, kAllocatorTagMonitorList>> Monitors; 363 364 private: 365 // During sweeping we may free an object and on a separate thread have an object created using 366 // the newly freed memory. That object may then have its lock-word inflated and a monitor created. 367 // If we allow new monitor registration during sweeping this monitor may be incorrectly freed as 368 // the object wasn't marked when sweeping began. 369 bool allow_new_monitors_ GUARDED_BY(monitor_list_lock_); 370 Mutex monitor_list_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER; 371 ConditionVariable monitor_add_condition_ GUARDED_BY(monitor_list_lock_); 372 Monitors list_ GUARDED_BY(monitor_list_lock_); 373 374 friend class Monitor; 375 DISALLOW_COPY_AND_ASSIGN(MonitorList); 376 }; 377 378 // Collects information about the current state of an object's monitor. 379 // This is very unsafe, and must only be called when all threads are suspended. 380 // For use only by the JDWP implementation. 381 class MonitorInfo { 382 public: MonitorInfo()383 MonitorInfo() : owner_(nullptr), entry_count_(0) {} 384 MonitorInfo(const MonitorInfo&) = default; 385 MonitorInfo& operator=(const MonitorInfo&) = default; 386 explicit MonitorInfo(ObjPtr<mirror::Object> o) REQUIRES(Locks::mutator_lock_); 387 388 Thread* owner_; 389 size_t entry_count_; 390 std::vector<Thread*> waiters_; 391 }; 392 393 } // namespace art 394 395 #endif // ART_RUNTIME_MONITOR_H_ 396