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 "atomic.h" 29 #include "base/allocator.h" 30 #include "base/mutex.h" 31 #include "gc_root.h" 32 #include "lock_word.h" 33 #include "object_callbacks.h" 34 #include "read_barrier_option.h" 35 #include "thread_state.h" 36 37 namespace art { 38 39 class ArtMethod; 40 class LockWord; 41 template<class T> class Handle; 42 class StackVisitor; 43 class Thread; 44 typedef uint32_t MonitorId; 45 46 namespace mirror { 47 class Object; 48 } // namespace mirror 49 50 class Monitor { 51 public: 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; 55 56 ~Monitor(); 57 58 static void Init(uint32_t lock_profiling_threshold); 59 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. 63 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_); 70 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_) 76 UNLOCK_FUNCTION(obj); 77 78 static void Notify(Thread* self, mirror::Object* obj) SHARED_REQUIRES(Locks::mutator_lock_) { 79 DoNotify(self, obj, false); 80 } 81 static void NotifyAll(Thread* self, mirror::Object* obj) SHARED_REQUIRES(Locks::mutator_lock_) { 82 DoNotify(self, obj, true); 83 } 84 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; 90 91 static void DescribeWait(std::ostream& os, const Thread* thread) 92 REQUIRES(!Locks::thread_suspend_count_lock_) 93 SHARED_REQUIRES(Locks::mutator_lock_); 94 95 // Used to implement JDWP's ThreadReference.CurrentContendedMonitor. 96 static mirror::Object* GetContendedMonitor(Thread* thread) 97 SHARED_REQUIRES(Locks::mutator_lock_); 98 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_); 106 107 static bool IsValidLockWord(LockWord lock_word); 108 109 template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier> 110 mirror::Object* GetObject() SHARED_REQUIRES(Locks::mutator_lock_) { 111 return obj_.Read<kReadBarrierOption>(); 112 } 113 114 void SetObject(mirror::Object* object); 115 116 Thread* GetOwner() const NO_THREAD_SAFETY_ANALYSIS { 117 return owner_; 118 } 119 120 int32_t GetHashCode(); 121 122 bool IsLocked() SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!monitor_lock_); 123 124 bool HasHashCode() const { 125 return hash_code_.LoadRelaxed() != 0; 126 } 127 128 MonitorId GetMonitorId() const { 129 return monitor_id_; 130 } 131 132 // 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_); 135 136 // 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; 141 142 #ifndef __LP64__ 143 void* operator new(size_t size) { 144 // Align Monitor* as per the monitor ID field size in the lock word. 145 void* result; 146 int error = posix_memalign(&result, LockWord::kMonitorIdAlignment, size); 147 CHECK_EQ(error, 0) << strerror(error); 148 return result; 149 } 150 151 void operator delete(void* ptr) { 152 free(ptr); 153 } 154 #endif 155 156 private: 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_); 161 162 // Install the monitor into its object, may fail if another thread installs a different monitor 163 // first. 164 bool Install(Thread* self) 165 REQUIRES(!monitor_lock_) 166 SHARED_REQUIRES(Locks::mutator_lock_); 167 168 // Links a thread into a monitor's wait set. The monitor lock must be held by the caller of this 169 // routine. 170 void AppendToWaitSet(Thread* thread) REQUIRES(monitor_lock_); 171 172 // Unlinks a thread from a monitor's wait set. The monitor lock must be held by the caller of 173 // this routine. 174 void RemoveFromWaitSet(Thread* thread) REQUIRES(monitor_lock_); 175 176 // 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) 183 184 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_); 187 188 static void FailedUnlock(mirror::Object* obj, 189 uint32_t expected_owner_thread_id, 190 uint32_t found_owner_thread_id, 191 Monitor* mon) 192 REQUIRES(!Locks::thread_list_lock_, 193 !monitor_lock_) 194 SHARED_REQUIRES(Locks::mutator_lock_); 195 196 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_); 202 203 static void DoNotify(Thread* self, mirror::Object* obj, bool notify_all) 204 SHARED_REQUIRES(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS; // For mon->Notify. 205 206 void Notify(Thread* self) 207 REQUIRES(!monitor_lock_) 208 SHARED_REQUIRES(Locks::mutator_lock_); 209 210 void NotifyAll(Thread* self) 211 REQUIRES(!monitor_lock_) 212 SHARED_REQUIRES(Locks::mutator_lock_); 213 214 static std::string PrettyContentionInfo(const std::string& owner_name, 215 pid_t owner_tid, 216 ArtMethod* owners_method, 217 uint32_t owners_dex_pc, 218 size_t num_waiters) 219 REQUIRES(!Locks::thread_list_lock_) 220 SHARED_REQUIRES(Locks::mutator_lock_); 221 222 // Wait on a monitor until timeout, interrupt, or notification. Used for Object.wait() and 223 // (somewhat indirectly) Thread.sleep() and Thread.join(). 224 // 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. 231 // 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. 234 // 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. 238 // 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_); 244 245 // 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_); 250 251 uint32_t GetOwnerThreadId() REQUIRES(!monitor_lock_); 252 253 // Support for systrace output of monitor operations. 254 ALWAYS_INLINE static void AtraceMonitorLock(Thread* self, 255 mirror::Object* obj, 256 bool is_wait) 257 SHARED_REQUIRES(Locks::mutator_lock_); 258 static void AtraceMonitorLockImpl(Thread* self, 259 mirror::Object* obj, 260 bool is_wait) 261 SHARED_REQUIRES(Locks::mutator_lock_); 262 ALWAYS_INLINE static void AtraceMonitorUnlock(); 263 264 static uint32_t lock_profiling_threshold_; 265 266 Mutex monitor_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER; 267 268 ConditionVariable monitor_contenders_ GUARDED_BY(monitor_lock_); 269 270 // Number of people waiting on the condition. 271 size_t num_waiters_ GUARDED_BY(monitor_lock_); 272 273 // Which thread currently owns the lock? 274 Thread* volatile owner_ GUARDED_BY(monitor_lock_); 275 276 // Owner's recursive lock depth. 277 int lock_count_ GUARDED_BY(monitor_lock_); 278 279 // 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_; 283 284 // Threads currently waiting on this monitor. 285 Thread* wait_set_ GUARDED_BY(monitor_lock_); 286 287 // Stored object hash code, generated lazily by GetHashCode. 288 AtomicInteger hash_code_; 289 290 // 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_); 295 296 // The denser encoded version of this monitor as stored in the lock word. 297 MonitorId monitor_id_; 298 299 #ifdef __LP64__ 300 // Free list for monitor pool. 301 Monitor* next_free_ GUARDED_BY(Locks::allocated_monitor_ids_lock_); 302 #endif 303 304 friend class MonitorInfo; 305 friend class MonitorList; 306 friend class MonitorPool; 307 friend class mirror::Object; 308 DISALLOW_COPY_AND_ASSIGN(Monitor); 309 }; 310 311 class MonitorList { 312 public: 313 MonitorList(); 314 ~MonitorList(); 315 316 void Add(Monitor* m) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!monitor_list_lock_); 317 318 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_); 325 326 typedef std::list<Monitor*, TrackingAllocator<Monitor*, kAllocatorTagMonitorList>> Monitors; 327 328 private: 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_); 337 338 friend class Monitor; 339 DISALLOW_COPY_AND_ASSIGN(MonitorList); 340 }; 341 342 // 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. 345 class MonitorInfo { 346 public: 347 MonitorInfo() = default; 348 MonitorInfo(const MonitorInfo&) = default; 349 MonitorInfo& operator=(const MonitorInfo&) = default; 350 explicit MonitorInfo(mirror::Object* o) REQUIRES(Locks::mutator_lock_); 351 352 Thread* owner_; 353 size_t entry_count_; 354 std::vector<Thread*> waiters_; 355 }; 356 357 } // namespace art 358 359 #endif // ART_RUNTIME_MONITOR_H_ 360
