mutex.h revision 3e5cf305db800b2989ad57b7cde8fb3cc9fa1b9e
1/* 2 * Copyright (C) 2011 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_BASE_MUTEX_H_ 18#define ART_RUNTIME_BASE_MUTEX_H_ 19 20#include <pthread.h> 21#include <stdint.h> 22 23#include <iosfwd> 24#include <string> 25 26#include "atomic.h" 27#include "base/logging.h" 28#include "base/macros.h" 29#include "globals.h" 30 31#if defined(__APPLE__) 32#define ART_USE_FUTEXES 0 33#else 34#define ART_USE_FUTEXES 1 35#endif 36 37// Currently Darwin doesn't support locks with timeouts. 38#if !defined(__APPLE__) 39#define HAVE_TIMED_RWLOCK 1 40#else 41#define HAVE_TIMED_RWLOCK 0 42#endif 43 44namespace art { 45 46class LOCKABLE ReaderWriterMutex; 47class ScopedContentionRecorder; 48class Thread; 49 50// LockLevel is used to impose a lock hierarchy [1] where acquisition of a Mutex at a higher or 51// equal level to a lock a thread holds is invalid. The lock hierarchy achieves a cycle free 52// partial ordering and thereby cause deadlock situations to fail checks. 53// 54// [1] http://www.drdobbs.com/parallel/use-lock-hierarchies-to-avoid-deadlock/204801163 55enum LockLevel { 56 kLoggingLock = 0, 57 kUnexpectedSignalLock, 58 kThreadSuspendCountLock, 59 kAbortLock, 60 kJdwpSocketLock, 61 kRosAllocGlobalLock, 62 kRosAllocBracketLock, 63 kRosAllocBulkFreeLock, 64 kAllocSpaceLock, 65 kReferenceProcessorLock, 66 kDexFileMethodInlinerLock, 67 kDexFileToMethodInlinerMapLock, 68 kMarkSweepMarkStackLock, 69 kTransactionLogLock, 70 kInternTableLock, 71 kMonitorPoolLock, 72 kDefaultMutexLevel, 73 kMarkSweepLargeObjectLock, 74 kPinTableLock, 75 kLoadLibraryLock, 76 kJdwpObjectRegistryLock, 77 kClassLinkerClassesLock, 78 kBreakpointLock, 79 kMonitorLock, 80 kMonitorListLock, 81 kThreadListLock, 82 kBreakpointInvokeLock, 83 kDeoptimizationLock, 84 kTraceLock, 85 kProfilerLock, 86 kJdwpEventListLock, 87 kJdwpAttachLock, 88 kJdwpStartLock, 89 kRuntimeShutdownLock, 90 kHeapBitmapLock, 91 kMutatorLock, 92 kZygoteCreationLock, 93 94 kLockLevelCount // Must come last. 95}; 96std::ostream& operator<<(std::ostream& os, const LockLevel& rhs); 97 98const bool kDebugLocking = kIsDebugBuild; 99 100// Record Log contention information, dumpable via SIGQUIT. 101#ifdef ART_USE_FUTEXES 102// To enable lock contention logging, set this to true. 103const bool kLogLockContentions = false; 104#else 105// Keep this false as lock contention logging is supported only with 106// futex. 107const bool kLogLockContentions = false; 108#endif 109const size_t kContentionLogSize = 4; 110const size_t kContentionLogDataSize = kLogLockContentions ? 1 : 0; 111const size_t kAllMutexDataSize = kLogLockContentions ? 1 : 0; 112 113// Base class for all Mutex implementations 114class BaseMutex { 115 public: 116 const char* GetName() const { 117 return name_; 118 } 119 120 virtual bool IsMutex() const { return false; } 121 virtual bool IsReaderWriterMutex() const { return false; } 122 123 virtual void Dump(std::ostream& os) const = 0; 124 125 static void DumpAll(std::ostream& os); 126 127 protected: 128 friend class ConditionVariable; 129 130 BaseMutex(const char* name, LockLevel level); 131 virtual ~BaseMutex(); 132 void RegisterAsLocked(Thread* self); 133 void RegisterAsUnlocked(Thread* self); 134 void CheckSafeToWait(Thread* self); 135 136 friend class ScopedContentionRecorder; 137 138 void RecordContention(uint64_t blocked_tid, uint64_t owner_tid, uint64_t nano_time_blocked); 139 void DumpContention(std::ostream& os) const; 140 141 const LockLevel level_; // Support for lock hierarchy. 142 const char* const name_; 143 144 // A log entry that records contention but makes no guarantee that either tid will be held live. 145 struct ContentionLogEntry { 146 ContentionLogEntry() : blocked_tid(0), owner_tid(0) {} 147 uint64_t blocked_tid; 148 uint64_t owner_tid; 149 AtomicInteger count; 150 }; 151 struct ContentionLogData { 152 ContentionLogEntry contention_log[kContentionLogSize]; 153 // The next entry in the contention log to be updated. Value ranges from 0 to 154 // kContentionLogSize - 1. 155 AtomicInteger cur_content_log_entry; 156 // Number of times the Mutex has been contended. 157 AtomicInteger contention_count; 158 // Sum of time waited by all contenders in ns. 159 volatile uint64_t wait_time; 160 void AddToWaitTime(uint64_t value); 161 ContentionLogData() : wait_time(0) {} 162 }; 163 ContentionLogData contention_log_data_[kContentionLogDataSize]; 164 165 public: 166 bool HasEverContended() const { 167 if (kLogLockContentions) { 168 return contention_log_data_->contention_count.LoadSequentiallyConsistent() > 0; 169 } 170 return false; 171 } 172}; 173 174// A Mutex is used to achieve mutual exclusion between threads. A Mutex can be used to gain 175// exclusive access to what it guards. A Mutex can be in one of two states: 176// - Free - not owned by any thread, 177// - Exclusive - owned by a single thread. 178// 179// The effect of locking and unlocking operations on the state is: 180// State | ExclusiveLock | ExclusiveUnlock 181// ------------------------------------------- 182// Free | Exclusive | error 183// Exclusive | Block* | Free 184// * Mutex is not reentrant and so an attempt to ExclusiveLock on the same thread will result in 185// an error. Being non-reentrant simplifies Waiting on ConditionVariables. 186std::ostream& operator<<(std::ostream& os, const Mutex& mu); 187class LOCKABLE Mutex : public BaseMutex { 188 public: 189 explicit Mutex(const char* name, LockLevel level = kDefaultMutexLevel, bool recursive = false); 190 ~Mutex(); 191 192 virtual bool IsMutex() const { return true; } 193 194 // Block until mutex is free then acquire exclusive access. 195 void ExclusiveLock(Thread* self) EXCLUSIVE_LOCK_FUNCTION(); 196 void Lock(Thread* self) EXCLUSIVE_LOCK_FUNCTION() { ExclusiveLock(self); } 197 198 // Returns true if acquires exclusive access, false otherwise. 199 bool ExclusiveTryLock(Thread* self) EXCLUSIVE_TRYLOCK_FUNCTION(true); 200 bool TryLock(Thread* self) EXCLUSIVE_TRYLOCK_FUNCTION(true) { return ExclusiveTryLock(self); } 201 202 // Release exclusive access. 203 void ExclusiveUnlock(Thread* self) UNLOCK_FUNCTION(); 204 void Unlock(Thread* self) UNLOCK_FUNCTION() { ExclusiveUnlock(self); } 205 206 // Is the current thread the exclusive holder of the Mutex. 207 bool IsExclusiveHeld(const Thread* self) const; 208 209 // Assert that the Mutex is exclusively held by the current thread. 210 void AssertExclusiveHeld(const Thread* self) { 211 if (kDebugLocking && (gAborting == 0)) { 212 CHECK(IsExclusiveHeld(self)) << *this; 213 } 214 } 215 void AssertHeld(const Thread* self) { AssertExclusiveHeld(self); } 216 217 // Assert that the Mutex is not held by the current thread. 218 void AssertNotHeldExclusive(const Thread* self) { 219 if (kDebugLocking && (gAborting == 0)) { 220 CHECK(!IsExclusiveHeld(self)) << *this; 221 } 222 } 223 void AssertNotHeld(const Thread* self) { AssertNotHeldExclusive(self); } 224 225 // Id associated with exclusive owner. 226 uint64_t GetExclusiveOwnerTid() const; 227 228 // Returns how many times this Mutex has been locked, it is better to use AssertHeld/NotHeld. 229 unsigned int GetDepth() const { 230 return recursion_count_; 231 } 232 233 virtual void Dump(std::ostream& os) const; 234 235 private: 236#if ART_USE_FUTEXES 237 // 0 is unheld, 1 is held. 238 volatile int32_t state_; 239 // Exclusive owner. 240 volatile uint64_t exclusive_owner_; 241 // Number of waiting contenders. 242 AtomicInteger num_contenders_; 243#else 244 pthread_mutex_t mutex_; 245#endif 246 const bool recursive_; // Can the lock be recursively held? 247 unsigned int recursion_count_; 248 friend class ConditionVariable; 249 DISALLOW_COPY_AND_ASSIGN(Mutex); 250}; 251 252// A ReaderWriterMutex is used to achieve mutual exclusion between threads, similar to a Mutex. 253// Unlike a Mutex a ReaderWriterMutex can be used to gain exclusive (writer) or shared (reader) 254// access to what it guards. A flaw in relation to a Mutex is that it cannot be used with a 255// condition variable. A ReaderWriterMutex can be in one of three states: 256// - Free - not owned by any thread, 257// - Exclusive - owned by a single thread, 258// - Shared(n) - shared amongst n threads. 259// 260// The effect of locking and unlocking operations on the state is: 261// 262// State | ExclusiveLock | ExclusiveUnlock | SharedLock | SharedUnlock 263// ---------------------------------------------------------------------------- 264// Free | Exclusive | error | SharedLock(1) | error 265// Exclusive | Block | Free | Block | error 266// Shared(n) | Block | error | SharedLock(n+1)* | Shared(n-1) or Free 267// * for large values of n the SharedLock may block. 268std::ostream& operator<<(std::ostream& os, const ReaderWriterMutex& mu); 269class LOCKABLE ReaderWriterMutex : public BaseMutex { 270 public: 271 explicit ReaderWriterMutex(const char* name, LockLevel level = kDefaultMutexLevel); 272 ~ReaderWriterMutex(); 273 274 virtual bool IsReaderWriterMutex() const { return true; } 275 276 // Block until ReaderWriterMutex is free then acquire exclusive access. 277 void ExclusiveLock(Thread* self) EXCLUSIVE_LOCK_FUNCTION(); 278 void WriterLock(Thread* self) EXCLUSIVE_LOCK_FUNCTION() { ExclusiveLock(self); } 279 280 // Release exclusive access. 281 void ExclusiveUnlock(Thread* self) UNLOCK_FUNCTION(); 282 void WriterUnlock(Thread* self) UNLOCK_FUNCTION() { ExclusiveUnlock(self); } 283 284 // Block until ReaderWriterMutex is free and acquire exclusive access. Returns true on success 285 // or false if timeout is reached. 286#if HAVE_TIMED_RWLOCK 287 bool ExclusiveLockWithTimeout(Thread* self, int64_t ms, int32_t ns) 288 EXCLUSIVE_TRYLOCK_FUNCTION(true); 289#endif 290 291 // Block until ReaderWriterMutex is shared or free then acquire a share on the access. 292 void SharedLock(Thread* self) SHARED_LOCK_FUNCTION() ALWAYS_INLINE; 293 void ReaderLock(Thread* self) SHARED_LOCK_FUNCTION() { SharedLock(self); } 294 295 // Try to acquire share of ReaderWriterMutex. 296 bool SharedTryLock(Thread* self) EXCLUSIVE_TRYLOCK_FUNCTION(true); 297 298 // Release a share of the access. 299 void SharedUnlock(Thread* self) UNLOCK_FUNCTION() ALWAYS_INLINE; 300 void ReaderUnlock(Thread* self) UNLOCK_FUNCTION() { SharedUnlock(self); } 301 302 // Is the current thread the exclusive holder of the ReaderWriterMutex. 303 bool IsExclusiveHeld(const Thread* self) const; 304 305 // Assert the current thread has exclusive access to the ReaderWriterMutex. 306 void AssertExclusiveHeld(const Thread* self) { 307 if (kDebugLocking && (gAborting == 0)) { 308 CHECK(IsExclusiveHeld(self)) << *this; 309 } 310 } 311 void AssertWriterHeld(const Thread* self) { AssertExclusiveHeld(self); } 312 313 // Assert the current thread doesn't have exclusive access to the ReaderWriterMutex. 314 void AssertNotExclusiveHeld(const Thread* self) { 315 if (kDebugLocking && (gAborting == 0)) { 316 CHECK(!IsExclusiveHeld(self)) << *this; 317 } 318 } 319 void AssertNotWriterHeld(const Thread* self) { AssertNotExclusiveHeld(self); } 320 321 // Is the current thread a shared holder of the ReaderWriterMutex. 322 bool IsSharedHeld(const Thread* self) const; 323 324 // Assert the current thread has shared access to the ReaderWriterMutex. 325 void AssertSharedHeld(const Thread* self) { 326 if (kDebugLocking && (gAborting == 0)) { 327 // TODO: we can only assert this well when self != NULL. 328 CHECK(IsSharedHeld(self) || self == NULL) << *this; 329 } 330 } 331 void AssertReaderHeld(const Thread* self) { AssertSharedHeld(self); } 332 333 // Assert the current thread doesn't hold this ReaderWriterMutex either in shared or exclusive 334 // mode. 335 void AssertNotHeld(const Thread* self) { 336 if (kDebugLocking && (gAborting == 0)) { 337 CHECK(!IsSharedHeld(self)) << *this; 338 } 339 } 340 341 // Id associated with exclusive owner. 342 uint64_t GetExclusiveOwnerTid() const; 343 344 virtual void Dump(std::ostream& os) const; 345 346 private: 347#if ART_USE_FUTEXES 348 // -1 implies held exclusive, +ve shared held by state_ many owners. 349 volatile int32_t state_; 350 // Exclusive owner. 351 volatile uint64_t exclusive_owner_; 352 // Pending readers. 353 volatile int32_t num_pending_readers_; 354 // Pending writers. 355 AtomicInteger num_pending_writers_; 356#else 357 pthread_rwlock_t rwlock_; 358#endif 359 DISALLOW_COPY_AND_ASSIGN(ReaderWriterMutex); 360}; 361 362// ConditionVariables allow threads to queue and sleep. Threads may then be resumed individually 363// (Signal) or all at once (Broadcast). 364class ConditionVariable { 365 public: 366 explicit ConditionVariable(const char* name, Mutex& mutex); 367 ~ConditionVariable(); 368 369 void Broadcast(Thread* self); 370 void Signal(Thread* self); 371 // TODO: No thread safety analysis on Wait and TimedWait as they call mutex operations via their 372 // pointer copy, thereby defeating annotalysis. 373 void Wait(Thread* self) NO_THREAD_SAFETY_ANALYSIS; 374 void TimedWait(Thread* self, int64_t ms, int32_t ns) NO_THREAD_SAFETY_ANALYSIS; 375 // Variant of Wait that should be used with caution. Doesn't validate that no mutexes are held 376 // when waiting. 377 // TODO: remove this. 378 void WaitHoldingLocks(Thread* self) NO_THREAD_SAFETY_ANALYSIS; 379 380 private: 381 const char* const name_; 382 // The Mutex being used by waiters. It is an error to mix condition variables between different 383 // Mutexes. 384 Mutex& guard_; 385#if ART_USE_FUTEXES 386 // A counter that is modified by signals and broadcasts. This ensures that when a waiter gives up 387 // their Mutex and another thread takes it and signals, the waiting thread observes that sequence_ 388 // changed and doesn't enter the wait. Modified while holding guard_, but is read by futex wait 389 // without guard_ held. 390 AtomicInteger sequence_; 391 // Number of threads that have come into to wait, not the length of the waiters on the futex as 392 // waiters may have been requeued onto guard_. Guarded by guard_. 393 volatile int32_t num_waiters_; 394#else 395 pthread_cond_t cond_; 396#endif 397 DISALLOW_COPY_AND_ASSIGN(ConditionVariable); 398}; 399 400// Scoped locker/unlocker for a regular Mutex that acquires mu upon construction and releases it 401// upon destruction. 402class SCOPED_LOCKABLE MutexLock { 403 public: 404 explicit MutexLock(Thread* self, Mutex& mu) EXCLUSIVE_LOCK_FUNCTION(mu) : self_(self), mu_(mu) { 405 mu_.ExclusiveLock(self_); 406 } 407 408 ~MutexLock() UNLOCK_FUNCTION() { 409 mu_.ExclusiveUnlock(self_); 410 } 411 412 private: 413 Thread* const self_; 414 Mutex& mu_; 415 DISALLOW_COPY_AND_ASSIGN(MutexLock); 416}; 417// Catch bug where variable name is omitted. "MutexLock (lock);" instead of "MutexLock mu(lock)". 418#define MutexLock(x) COMPILE_ASSERT(0, mutex_lock_declaration_missing_variable_name) 419 420// Scoped locker/unlocker for a ReaderWriterMutex that acquires read access to mu upon 421// construction and releases it upon destruction. 422class SCOPED_LOCKABLE ReaderMutexLock { 423 public: 424 explicit ReaderMutexLock(Thread* self, ReaderWriterMutex& mu) EXCLUSIVE_LOCK_FUNCTION(mu) : 425 self_(self), mu_(mu) { 426 mu_.SharedLock(self_); 427 } 428 429 ~ReaderMutexLock() UNLOCK_FUNCTION() { 430 mu_.SharedUnlock(self_); 431 } 432 433 private: 434 Thread* const self_; 435 ReaderWriterMutex& mu_; 436 DISALLOW_COPY_AND_ASSIGN(ReaderMutexLock); 437}; 438// Catch bug where variable name is omitted. "ReaderMutexLock (lock);" instead of 439// "ReaderMutexLock mu(lock)". 440#define ReaderMutexLock(x) COMPILE_ASSERT(0, reader_mutex_lock_declaration_missing_variable_name) 441 442// Scoped locker/unlocker for a ReaderWriterMutex that acquires write access to mu upon 443// construction and releases it upon destruction. 444class SCOPED_LOCKABLE WriterMutexLock { 445 public: 446 explicit WriterMutexLock(Thread* self, ReaderWriterMutex& mu) EXCLUSIVE_LOCK_FUNCTION(mu) : 447 self_(self), mu_(mu) { 448 mu_.ExclusiveLock(self_); 449 } 450 451 ~WriterMutexLock() UNLOCK_FUNCTION() { 452 mu_.ExclusiveUnlock(self_); 453 } 454 455 private: 456 Thread* const self_; 457 ReaderWriterMutex& mu_; 458 DISALLOW_COPY_AND_ASSIGN(WriterMutexLock); 459}; 460// Catch bug where variable name is omitted. "WriterMutexLock (lock);" instead of 461// "WriterMutexLock mu(lock)". 462#define WriterMutexLock(x) COMPILE_ASSERT(0, writer_mutex_lock_declaration_missing_variable_name) 463 464// Global mutexes corresponding to the levels above. 465class Locks { 466 public: 467 static void Init(); 468 469 // The mutator_lock_ is used to allow mutators to execute in a shared (reader) mode or to block 470 // mutators by having an exclusive (writer) owner. In normal execution each mutator thread holds 471 // a share on the mutator_lock_. The garbage collector may also execute with shared access but 472 // at times requires exclusive access to the heap (not to be confused with the heap meta-data 473 // guarded by the heap_lock_ below). When the garbage collector requires exclusive access it asks 474 // the mutators to suspend themselves which also involves usage of the thread_suspend_count_lock_ 475 // to cover weaknesses in using ReaderWriterMutexes with ConditionVariables. We use a condition 476 // variable to wait upon in the suspension logic as releasing and then re-acquiring a share on 477 // the mutator lock doesn't necessarily allow the exclusive user (e.g the garbage collector) 478 // chance to acquire the lock. 479 // 480 // Thread suspension: 481 // Shared users | Exclusive user 482 // (holding mutator lock and in kRunnable state) | .. running .. 483 // .. running .. | Request thread suspension by: 484 // .. running .. | - acquiring thread_suspend_count_lock_ 485 // .. running .. | - incrementing Thread::suspend_count_ on 486 // .. running .. | all mutator threads 487 // .. running .. | - releasing thread_suspend_count_lock_ 488 // .. running .. | Block trying to acquire exclusive mutator lock 489 // Poll Thread::suspend_count_ and enter full | .. blocked .. 490 // suspend code. | .. blocked .. 491 // Change state to kSuspended | .. blocked .. 492 // x: Release share on mutator_lock_ | Carry out exclusive access 493 // Acquire thread_suspend_count_lock_ | .. exclusive .. 494 // while Thread::suspend_count_ > 0 | .. exclusive .. 495 // - wait on Thread::resume_cond_ | .. exclusive .. 496 // (releases thread_suspend_count_lock_) | .. exclusive .. 497 // .. waiting .. | Release mutator_lock_ 498 // .. waiting .. | Request thread resumption by: 499 // .. waiting .. | - acquiring thread_suspend_count_lock_ 500 // .. waiting .. | - decrementing Thread::suspend_count_ on 501 // .. waiting .. | all mutator threads 502 // .. waiting .. | - notifying on Thread::resume_cond_ 503 // - re-acquire thread_suspend_count_lock_ | - releasing thread_suspend_count_lock_ 504 // Release thread_suspend_count_lock_ | .. running .. 505 // Acquire share on mutator_lock_ | .. running .. 506 // - This could block but the thread still | .. running .. 507 // has a state of kSuspended and so this | .. running .. 508 // isn't an issue. | .. running .. 509 // Acquire thread_suspend_count_lock_ | .. running .. 510 // - we poll here as we're transitioning into | .. running .. 511 // kRunnable and an individual thread suspend | .. running .. 512 // request (e.g for debugging) won't try | .. running .. 513 // to acquire the mutator lock (which would | .. running .. 514 // block as we hold the mutator lock). This | .. running .. 515 // poll ensures that if the suspender thought | .. running .. 516 // we were suspended by incrementing our | .. running .. 517 // Thread::suspend_count_ and then reading | .. running .. 518 // our state we go back to waiting on | .. running .. 519 // Thread::resume_cond_. | .. running .. 520 // can_go_runnable = Thread::suspend_count_ == 0 | .. running .. 521 // Release thread_suspend_count_lock_ | .. running .. 522 // if can_go_runnable | .. running .. 523 // Change state to kRunnable | .. running .. 524 // else | .. running .. 525 // Goto x | .. running .. 526 // .. running .. | .. running .. 527 static ReaderWriterMutex* mutator_lock_; 528 529 // Allow reader-writer mutual exclusion on the mark and live bitmaps of the heap. 530 static ReaderWriterMutex* heap_bitmap_lock_ ACQUIRED_AFTER(mutator_lock_); 531 532 // Guards shutdown of the runtime. 533 static Mutex* runtime_shutdown_lock_ ACQUIRED_AFTER(heap_bitmap_lock_); 534 535 // The thread_list_lock_ guards ThreadList::list_. It is also commonly held to stop threads 536 // attaching and detaching. 537 static Mutex* thread_list_lock_ ACQUIRED_AFTER(runtime_shutdown_lock_); 538 539 // Guards breakpoints. 540 static Mutex* breakpoint_lock_ ACQUIRED_AFTER(thread_list_lock_); 541 542 // Guards trace requests. 543 static Mutex* trace_lock_ ACQUIRED_AFTER(breakpoint_lock_); 544 545 // Guards profile objects. 546 static Mutex* profiler_lock_ ACQUIRED_AFTER(trace_lock_); 547 548 // Guards lists of classes within the class linker. 549 static ReaderWriterMutex* classlinker_classes_lock_ ACQUIRED_AFTER(profiler_lock_); 550 551 // When declaring any Mutex add DEFAULT_MUTEX_ACQUIRED_AFTER to use annotalysis to check the code 552 // doesn't try to hold a higher level Mutex. 553 #define DEFAULT_MUTEX_ACQUIRED_AFTER ACQUIRED_AFTER(Locks::classlinker_classes_lock_) 554 555 // Guards intern table. 556 static Mutex* intern_table_lock_ ACQUIRED_AFTER(classlinker_classes_lock_); 557 558 // Have an exclusive aborting thread. 559 static Mutex* abort_lock_ ACQUIRED_AFTER(classlinker_classes_lock_); 560 561 // Allow mutual exclusion when manipulating Thread::suspend_count_. 562 // TODO: Does the trade-off of a per-thread lock make sense? 563 static Mutex* thread_suspend_count_lock_ ACQUIRED_AFTER(abort_lock_); 564 565 // One unexpected signal at a time lock. 566 static Mutex* unexpected_signal_lock_ ACQUIRED_AFTER(thread_suspend_count_lock_); 567 568 // Have an exclusive logging thread. 569 static Mutex* logging_lock_ ACQUIRED_AFTER(unexpected_signal_lock_); 570}; 571 572} // namespace art 573 574#endif // ART_RUNTIME_BASE_MUTEX_H_ 575