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 bool IsSensitiveThread(); 59 static void Init(uint32_t lock_profiling_threshold, bool (*is_sensitive_thread_hook)()); 60 61 // Return the thread id of the lock owner or 0 when there is no owner. 62 static uint32_t GetLockOwnerThreadId(mirror::Object* obj) 63 NO_THREAD_SAFETY_ANALYSIS; // TODO: Reading lock owner without holding lock is racy. 64 65 static mirror::Object* MonitorEnter(Thread* thread, mirror::Object* obj) 66 EXCLUSIVE_LOCK_FUNCTION(obj) 67 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 68 static bool MonitorExit(Thread* thread, mirror::Object* obj) 69 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 70 UNLOCK_FUNCTION(obj); 71 Notify(Thread * self,mirror::Object * obj)72 static void Notify(Thread* self, mirror::Object* obj) 73 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) { 74 DoNotify(self, obj, false); 75 } NotifyAll(Thread * self,mirror::Object * obj)76 static void NotifyAll(Thread* self, mirror::Object* obj) 77 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) { 78 DoNotify(self, obj, true); 79 } 80 81 // Object.wait(). Also called for class init. 82 static void Wait(Thread* self, mirror::Object* obj, int64_t ms, int32_t ns, 83 bool interruptShouldThrow, ThreadState why) 84 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 85 86 static void DescribeWait(std::ostream& os, const Thread* thread) 87 LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_) 88 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 89 90 // Used to implement JDWP's ThreadReference.CurrentContendedMonitor. 91 static mirror::Object* GetContendedMonitor(Thread* thread) 92 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 93 94 // Calls 'callback' once for each lock held in the single stack frame represented by 95 // the current state of 'stack_visitor'. 96 // The abort_on_failure flag allows to not die when the state of the runtime is unorderly. This 97 // is necessary when we have already aborted but want to dump the stack as much as we can. 98 static void VisitLocks(StackVisitor* stack_visitor, void (*callback)(mirror::Object*, void*), 99 void* callback_context, bool abort_on_failure = true) 100 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 101 102 static bool IsValidLockWord(LockWord lock_word); 103 104 template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier> GetObject()105 mirror::Object* GetObject() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) { 106 return obj_.Read<kReadBarrierOption>(); 107 } 108 109 void SetObject(mirror::Object* object); 110 GetOwner()111 Thread* GetOwner() const NO_THREAD_SAFETY_ANALYSIS { 112 return owner_; 113 } 114 115 int32_t GetHashCode(); 116 117 bool IsLocked() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 118 HasHashCode()119 bool HasHashCode() const { 120 return hash_code_.LoadRelaxed() != 0; 121 } 122 GetMonitorId()123 MonitorId GetMonitorId() const { 124 return monitor_id_; 125 } 126 127 // Inflate the lock on obj. May fail to inflate for spurious reasons, always re-check. 128 static void InflateThinLocked(Thread* self, Handle<mirror::Object> obj, LockWord lock_word, 129 uint32_t hash_code) NO_THREAD_SAFETY_ANALYSIS; 130 131 static bool Deflate(Thread* self, mirror::Object* obj) 132 // Not exclusive because ImageWriter calls this during a Heap::VisitObjects() that 133 // does not allow a thread suspension in the middle. TODO: maybe make this exclusive. 134 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 135 136 #ifndef __LP64__ new(size_t size)137 void* operator new(size_t size) { 138 // Align Monitor* as per the monitor ID field size in the lock word. 139 void* result; 140 int error = posix_memalign(&result, LockWord::kMonitorIdAlignment, size); 141 CHECK_EQ(error, 0) << strerror(error); 142 return result; 143 } 144 delete(void * ptr)145 void operator delete(void* ptr) { 146 free(ptr); 147 } 148 #endif 149 150 private: 151 explicit Monitor(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code) 152 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 153 explicit Monitor(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code, 154 MonitorId id) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 155 156 // Install the monitor into its object, may fail if another thread installs a different monitor 157 // first. 158 bool Install(Thread* self) 159 LOCKS_EXCLUDED(monitor_lock_) 160 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 161 162 // Links a thread into a monitor's wait set. The monitor lock must be held by the caller of this 163 // routine. 164 void AppendToWaitSet(Thread* thread) EXCLUSIVE_LOCKS_REQUIRED(monitor_lock_); 165 166 // Unlinks a thread from a monitor's wait set. The monitor lock must be held by the caller of 167 // this routine. 168 void RemoveFromWaitSet(Thread* thread) EXCLUSIVE_LOCKS_REQUIRED(monitor_lock_); 169 170 // Changes the shape of a monitor from thin to fat, preserving the internal lock state. The 171 // calling thread must own the lock or the owner must be suspended. There's a race with other 172 // threads inflating the lock, installing hash codes and spurious failures. The caller should 173 // re-read the lock word following the call. 174 static void Inflate(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code) 175 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 176 177 void LogContentionEvent(Thread* self, uint32_t wait_ms, uint32_t sample_percent, 178 const char* owner_filename, uint32_t owner_line_number) 179 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 180 181 static void FailedUnlock(mirror::Object* obj, Thread* expected_owner, Thread* found_owner, 182 Monitor* mon) 183 LOCKS_EXCLUDED(Locks::thread_list_lock_) 184 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 185 186 void Lock(Thread* self) 187 LOCKS_EXCLUDED(monitor_lock_) 188 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 189 bool Unlock(Thread* thread) 190 LOCKS_EXCLUDED(monitor_lock_) 191 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 192 193 static void DoNotify(Thread* self, mirror::Object* obj, bool notify_all) 194 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 195 196 void Notify(Thread* self) 197 LOCKS_EXCLUDED(monitor_lock_) 198 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 199 200 void NotifyAll(Thread* self) 201 LOCKS_EXCLUDED(monitor_lock_) 202 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 203 204 205 // Wait on a monitor until timeout, interrupt, or notification. Used for Object.wait() and 206 // (somewhat indirectly) Thread.sleep() and Thread.join(). 207 // 208 // If another thread calls Thread.interrupt(), we throw InterruptedException and return 209 // immediately if one of the following are true: 210 // - blocked in wait(), wait(long), or wait(long, int) methods of Object 211 // - blocked in join(), join(long), or join(long, int) methods of Thread 212 // - blocked in sleep(long), or sleep(long, int) methods of Thread 213 // Otherwise, we set the "interrupted" flag. 214 // 215 // Checks to make sure that "ns" is in the range 0-999999 (i.e. fractions of a millisecond) and 216 // throws the appropriate exception if it isn't. 217 // 218 // The spec allows "spurious wakeups", and recommends that all code using Object.wait() do so in 219 // a loop. This appears to derive from concerns about pthread_cond_wait() on multiprocessor 220 // systems. Some commentary on the web casts doubt on whether these can/should occur. 221 // 222 // Since we're allowed to wake up "early", we clamp extremely long durations to return at the end 223 // of the 32-bit time epoch. 224 void Wait(Thread* self, int64_t msec, int32_t nsec, bool interruptShouldThrow, ThreadState why) 225 LOCKS_EXCLUDED(monitor_lock_) 226 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 227 228 // Translates the provided method and pc into its declaring class' source file and line number. 229 void TranslateLocation(ArtMethod* method, uint32_t pc, 230 const char** source_file, uint32_t* line_number) const 231 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 232 233 uint32_t GetOwnerThreadId(); 234 235 static bool (*is_sensitive_thread_hook_)(); 236 static uint32_t lock_profiling_threshold_; 237 238 Mutex monitor_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER; 239 240 ConditionVariable monitor_contenders_ GUARDED_BY(monitor_lock_); 241 242 // Number of people waiting on the condition. 243 size_t num_waiters_ GUARDED_BY(monitor_lock_); 244 245 // Which thread currently owns the lock? 246 Thread* volatile owner_ GUARDED_BY(monitor_lock_); 247 248 // Owner's recursive lock depth. 249 int lock_count_ GUARDED_BY(monitor_lock_); 250 251 // What object are we part of. This is a weak root. Do not access 252 // this directly, use GetObject() to read it so it will be guarded 253 // by a read barrier. 254 GcRoot<mirror::Object> obj_; 255 256 // Threads currently waiting on this monitor. 257 Thread* wait_set_ GUARDED_BY(monitor_lock_); 258 259 // Stored object hash code, generated lazily by GetHashCode. 260 AtomicInteger hash_code_; 261 262 // Method and dex pc where the lock owner acquired the lock, used when lock 263 // sampling is enabled. locking_method_ may be null if the lock is currently 264 // unlocked, or if the lock is acquired by the system when the stack is empty. 265 ArtMethod* locking_method_ GUARDED_BY(monitor_lock_); 266 uint32_t locking_dex_pc_ GUARDED_BY(monitor_lock_); 267 268 // The denser encoded version of this monitor as stored in the lock word. 269 MonitorId monitor_id_; 270 271 #ifdef __LP64__ 272 // Free list for monitor pool. 273 Monitor* next_free_ GUARDED_BY(Locks::allocated_monitor_ids_lock_); 274 #endif 275 276 friend class MonitorInfo; 277 friend class MonitorList; 278 friend class MonitorPool; 279 friend class mirror::Object; 280 DISALLOW_COPY_AND_ASSIGN(Monitor); 281 }; 282 283 class MonitorList { 284 public: 285 MonitorList(); 286 ~MonitorList(); 287 288 void Add(Monitor* m) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 289 290 void SweepMonitorList(IsMarkedCallback* callback, void* arg) 291 LOCKS_EXCLUDED(monitor_list_lock_) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 292 void DisallowNewMonitors() LOCKS_EXCLUDED(monitor_list_lock_); 293 void AllowNewMonitors() LOCKS_EXCLUDED(monitor_list_lock_); 294 void EnsureNewMonitorsDisallowed() LOCKS_EXCLUDED(monitor_list_lock_); 295 // Returns how many monitors were deflated. 296 size_t DeflateMonitors() LOCKS_EXCLUDED(monitor_list_lock_) 297 EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_); 298 299 typedef std::list<Monitor*, TrackingAllocator<Monitor*, kAllocatorTagMonitorList>> Monitors; 300 301 private: 302 // During sweeping we may free an object and on a separate thread have an object created using 303 // the newly freed memory. That object may then have its lock-word inflated and a monitor created. 304 // If we allow new monitor registration during sweeping this monitor may be incorrectly freed as 305 // the object wasn't marked when sweeping began. 306 bool allow_new_monitors_ GUARDED_BY(monitor_list_lock_); 307 Mutex monitor_list_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER; 308 ConditionVariable monitor_add_condition_ GUARDED_BY(monitor_list_lock_); 309 Monitors list_ GUARDED_BY(monitor_list_lock_); 310 311 friend class Monitor; 312 DISALLOW_COPY_AND_ASSIGN(MonitorList); 313 }; 314 315 // Collects information about the current state of an object's monitor. 316 // This is very unsafe, and must only be called when all threads are suspended. 317 // For use only by the JDWP implementation. 318 class MonitorInfo { 319 public: 320 explicit MonitorInfo(mirror::Object* o) EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_); 321 322 Thread* owner_; 323 size_t entry_count_; 324 std::vector<Thread*> waiters_; 325 326 private: 327 DISALLOW_COPY_AND_ASSIGN(MonitorInfo); 328 }; 329 330 } // namespace art 331 332 #endif // ART_RUNTIME_MONITOR_H_ 333