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 #include "mutex.h"
18
19 #include <errno.h>
20 #include <sys/time.h>
21
22 #include "atomic.h"
23 #include "base/logging.h"
24 #include "mutex-inl.h"
25 #include "runtime.h"
26 #include "scoped_thread_state_change.h"
27 #include "thread-inl.h"
28 #include "utils.h"
29
30 namespace art {
31
32 Mutex* Locks::abort_lock_ = nullptr;
33 Mutex* Locks::alloc_tracker_lock_ = nullptr;
34 Mutex* Locks::allocated_monitor_ids_lock_ = nullptr;
35 Mutex* Locks::allocated_thread_ids_lock_ = nullptr;
36 ReaderWriterMutex* Locks::breakpoint_lock_ = nullptr;
37 ReaderWriterMutex* Locks::classlinker_classes_lock_ = nullptr;
38 Mutex* Locks::deoptimization_lock_ = nullptr;
39 ReaderWriterMutex* Locks::heap_bitmap_lock_ = nullptr;
40 Mutex* Locks::instrument_entrypoints_lock_ = nullptr;
41 Mutex* Locks::intern_table_lock_ = nullptr;
42 Mutex* Locks::logging_lock_ = nullptr;
43 Mutex* Locks::mem_maps_lock_ = nullptr;
44 Mutex* Locks::modify_ldt_lock_ = nullptr;
45 ReaderWriterMutex* Locks::mutator_lock_ = nullptr;
46 Mutex* Locks::profiler_lock_ = nullptr;
47 Mutex* Locks::reference_processor_lock_ = nullptr;
48 Mutex* Locks::reference_queue_cleared_references_lock_ = nullptr;
49 Mutex* Locks::reference_queue_finalizer_references_lock_ = nullptr;
50 Mutex* Locks::reference_queue_phantom_references_lock_ = nullptr;
51 Mutex* Locks::reference_queue_soft_references_lock_ = nullptr;
52 Mutex* Locks::reference_queue_weak_references_lock_ = nullptr;
53 Mutex* Locks::runtime_shutdown_lock_ = nullptr;
54 Mutex* Locks::thread_list_lock_ = nullptr;
55 Mutex* Locks::thread_list_suspend_thread_lock_ = nullptr;
56 Mutex* Locks::thread_suspend_count_lock_ = nullptr;
57 Mutex* Locks::trace_lock_ = nullptr;
58 Mutex* Locks::unexpected_signal_lock_ = nullptr;
59
60 struct AllMutexData {
61 // A guard for all_mutexes_ that's not a mutex (Mutexes must CAS to acquire and busy wait).
62 Atomic<const BaseMutex*> all_mutexes_guard;
63 // All created mutexes guarded by all_mutexes_guard_.
64 std::set<BaseMutex*>* all_mutexes;
AllMutexDataart::AllMutexData65 AllMutexData() : all_mutexes(NULL) {}
66 };
67 static struct AllMutexData gAllMutexData[kAllMutexDataSize];
68
69 #if ART_USE_FUTEXES
ComputeRelativeTimeSpec(timespec * result_ts,const timespec & lhs,const timespec & rhs)70 static bool ComputeRelativeTimeSpec(timespec* result_ts, const timespec& lhs, const timespec& rhs) {
71 const int32_t one_sec = 1000 * 1000 * 1000; // one second in nanoseconds.
72 result_ts->tv_sec = lhs.tv_sec - rhs.tv_sec;
73 result_ts->tv_nsec = lhs.tv_nsec - rhs.tv_nsec;
74 if (result_ts->tv_nsec < 0) {
75 result_ts->tv_sec--;
76 result_ts->tv_nsec += one_sec;
77 } else if (result_ts->tv_nsec > one_sec) {
78 result_ts->tv_sec++;
79 result_ts->tv_nsec -= one_sec;
80 }
81 return result_ts->tv_sec < 0;
82 }
83 #endif
84
85 class ScopedAllMutexesLock {
86 public:
ScopedAllMutexesLock(const BaseMutex * mutex)87 explicit ScopedAllMutexesLock(const BaseMutex* mutex) : mutex_(mutex) {
88 while (!gAllMutexData->all_mutexes_guard.CompareExchangeWeakAcquire(0, mutex)) {
89 NanoSleep(100);
90 }
91 }
~ScopedAllMutexesLock()92 ~ScopedAllMutexesLock() {
93 while (!gAllMutexData->all_mutexes_guard.CompareExchangeWeakRelease(mutex_, 0)) {
94 NanoSleep(100);
95 }
96 }
97 private:
98 const BaseMutex* const mutex_;
99 };
100
BaseMutex(const char * name,LockLevel level)101 BaseMutex::BaseMutex(const char* name, LockLevel level) : level_(level), name_(name) {
102 if (kLogLockContentions) {
103 ScopedAllMutexesLock mu(this);
104 std::set<BaseMutex*>** all_mutexes_ptr = &gAllMutexData->all_mutexes;
105 if (*all_mutexes_ptr == NULL) {
106 // We leak the global set of all mutexes to avoid ordering issues in global variable
107 // construction/destruction.
108 *all_mutexes_ptr = new std::set<BaseMutex*>();
109 }
110 (*all_mutexes_ptr)->insert(this);
111 }
112 }
113
~BaseMutex()114 BaseMutex::~BaseMutex() {
115 if (kLogLockContentions) {
116 ScopedAllMutexesLock mu(this);
117 gAllMutexData->all_mutexes->erase(this);
118 }
119 }
120
DumpAll(std::ostream & os)121 void BaseMutex::DumpAll(std::ostream& os) {
122 if (kLogLockContentions) {
123 os << "Mutex logging:\n";
124 ScopedAllMutexesLock mu(reinterpret_cast<const BaseMutex*>(-1));
125 std::set<BaseMutex*>* all_mutexes = gAllMutexData->all_mutexes;
126 if (all_mutexes == NULL) {
127 // No mutexes have been created yet during at startup.
128 return;
129 }
130 typedef std::set<BaseMutex*>::const_iterator It;
131 os << "(Contended)\n";
132 for (It it = all_mutexes->begin(); it != all_mutexes->end(); ++it) {
133 BaseMutex* mutex = *it;
134 if (mutex->HasEverContended()) {
135 mutex->Dump(os);
136 os << "\n";
137 }
138 }
139 os << "(Never contented)\n";
140 for (It it = all_mutexes->begin(); it != all_mutexes->end(); ++it) {
141 BaseMutex* mutex = *it;
142 if (!mutex->HasEverContended()) {
143 mutex->Dump(os);
144 os << "\n";
145 }
146 }
147 }
148 }
149
CheckSafeToWait(Thread * self)150 void BaseMutex::CheckSafeToWait(Thread* self) {
151 if (self == NULL) {
152 CheckUnattachedThread(level_);
153 return;
154 }
155 if (kDebugLocking) {
156 CHECK(self->GetHeldMutex(level_) == this || level_ == kMonitorLock)
157 << "Waiting on unacquired mutex: " << name_;
158 bool bad_mutexes_held = false;
159 for (int i = kLockLevelCount - 1; i >= 0; --i) {
160 if (i != level_) {
161 BaseMutex* held_mutex = self->GetHeldMutex(static_cast<LockLevel>(i));
162 // We expect waits to happen while holding the thread list suspend thread lock.
163 if (held_mutex != NULL && i != kThreadListSuspendThreadLock) {
164 LOG(ERROR) << "Holding \"" << held_mutex->name_ << "\" "
165 << "(level " << LockLevel(i) << ") while performing wait on "
166 << "\"" << name_ << "\" (level " << level_ << ")";
167 bad_mutexes_held = true;
168 }
169 }
170 }
171 CHECK(!bad_mutexes_held);
172 }
173 }
174
AddToWaitTime(uint64_t value)175 void BaseMutex::ContentionLogData::AddToWaitTime(uint64_t value) {
176 if (kLogLockContentions) {
177 // Atomically add value to wait_time.
178 wait_time.FetchAndAddSequentiallyConsistent(value);
179 }
180 }
181
RecordContention(uint64_t blocked_tid,uint64_t owner_tid,uint64_t nano_time_blocked)182 void BaseMutex::RecordContention(uint64_t blocked_tid,
183 uint64_t owner_tid,
184 uint64_t nano_time_blocked) {
185 if (kLogLockContentions) {
186 ContentionLogData* data = contention_log_data_;
187 ++(data->contention_count);
188 data->AddToWaitTime(nano_time_blocked);
189 ContentionLogEntry* log = data->contention_log;
190 // This code is intentionally racy as it is only used for diagnostics.
191 uint32_t slot = data->cur_content_log_entry.LoadRelaxed();
192 if (log[slot].blocked_tid == blocked_tid &&
193 log[slot].owner_tid == blocked_tid) {
194 ++log[slot].count;
195 } else {
196 uint32_t new_slot;
197 do {
198 slot = data->cur_content_log_entry.LoadRelaxed();
199 new_slot = (slot + 1) % kContentionLogSize;
200 } while (!data->cur_content_log_entry.CompareExchangeWeakRelaxed(slot, new_slot));
201 log[new_slot].blocked_tid = blocked_tid;
202 log[new_slot].owner_tid = owner_tid;
203 log[new_slot].count.StoreRelaxed(1);
204 }
205 }
206 }
207
DumpContention(std::ostream & os) const208 void BaseMutex::DumpContention(std::ostream& os) const {
209 if (kLogLockContentions) {
210 const ContentionLogData* data = contention_log_data_;
211 const ContentionLogEntry* log = data->contention_log;
212 uint64_t wait_time = data->wait_time.LoadRelaxed();
213 uint32_t contention_count = data->contention_count.LoadRelaxed();
214 if (contention_count == 0) {
215 os << "never contended";
216 } else {
217 os << "contended " << contention_count
218 << " total wait of contender " << PrettyDuration(wait_time)
219 << " average " << PrettyDuration(wait_time / contention_count);
220 SafeMap<uint64_t, size_t> most_common_blocker;
221 SafeMap<uint64_t, size_t> most_common_blocked;
222 for (size_t i = 0; i < kContentionLogSize; ++i) {
223 uint64_t blocked_tid = log[i].blocked_tid;
224 uint64_t owner_tid = log[i].owner_tid;
225 uint32_t count = log[i].count.LoadRelaxed();
226 if (count > 0) {
227 auto it = most_common_blocked.find(blocked_tid);
228 if (it != most_common_blocked.end()) {
229 most_common_blocked.Overwrite(blocked_tid, it->second + count);
230 } else {
231 most_common_blocked.Put(blocked_tid, count);
232 }
233 it = most_common_blocker.find(owner_tid);
234 if (it != most_common_blocker.end()) {
235 most_common_blocker.Overwrite(owner_tid, it->second + count);
236 } else {
237 most_common_blocker.Put(owner_tid, count);
238 }
239 }
240 }
241 uint64_t max_tid = 0;
242 size_t max_tid_count = 0;
243 for (const auto& pair : most_common_blocked) {
244 if (pair.second > max_tid_count) {
245 max_tid = pair.first;
246 max_tid_count = pair.second;
247 }
248 }
249 if (max_tid != 0) {
250 os << " sample shows most blocked tid=" << max_tid;
251 }
252 max_tid = 0;
253 max_tid_count = 0;
254 for (const auto& pair : most_common_blocker) {
255 if (pair.second > max_tid_count) {
256 max_tid = pair.first;
257 max_tid_count = pair.second;
258 }
259 }
260 if (max_tid != 0) {
261 os << " sample shows tid=" << max_tid << " owning during this time";
262 }
263 }
264 }
265 }
266
267
Mutex(const char * name,LockLevel level,bool recursive)268 Mutex::Mutex(const char* name, LockLevel level, bool recursive)
269 : BaseMutex(name, level), recursive_(recursive), recursion_count_(0) {
270 #if ART_USE_FUTEXES
271 DCHECK_EQ(0, state_.LoadRelaxed());
272 DCHECK_EQ(0, num_contenders_.LoadRelaxed());
273 #else
274 CHECK_MUTEX_CALL(pthread_mutex_init, (&mutex_, nullptr));
275 #endif
276 exclusive_owner_ = 0;
277 }
278
~Mutex()279 Mutex::~Mutex() {
280 #if ART_USE_FUTEXES
281 if (state_.LoadRelaxed() != 0) {
282 Runtime* runtime = Runtime::Current();
283 bool shutting_down = runtime == nullptr || runtime->IsShuttingDown(Thread::Current());
284 LOG(shutting_down ? WARNING : FATAL) << "destroying mutex with owner: " << exclusive_owner_;
285 } else {
286 CHECK_EQ(exclusive_owner_, 0U) << "unexpectedly found an owner on unlocked mutex " << name_;
287 CHECK_EQ(num_contenders_.LoadSequentiallyConsistent(), 0)
288 << "unexpectedly found a contender on mutex " << name_;
289 }
290 #else
291 // We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
292 // may still be using locks.
293 int rc = pthread_mutex_destroy(&mutex_);
294 if (rc != 0) {
295 errno = rc;
296 // TODO: should we just not log at all if shutting down? this could be the logging mutex!
297 MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
298 Runtime* runtime = Runtime::Current();
299 bool shutting_down = (runtime == NULL) || runtime->IsShuttingDownLocked();
300 PLOG(shutting_down ? WARNING : FATAL) << "pthread_mutex_destroy failed for " << name_;
301 }
302 #endif
303 }
304
ExclusiveLock(Thread * self)305 void Mutex::ExclusiveLock(Thread* self) {
306 DCHECK(self == NULL || self == Thread::Current());
307 if (kDebugLocking && !recursive_) {
308 AssertNotHeld(self);
309 }
310 if (!recursive_ || !IsExclusiveHeld(self)) {
311 #if ART_USE_FUTEXES
312 bool done = false;
313 do {
314 int32_t cur_state = state_.LoadRelaxed();
315 if (LIKELY(cur_state == 0)) {
316 // Change state from 0 to 1 and impose load/store ordering appropriate for lock acquisition.
317 done = state_.CompareExchangeWeakAcquire(0 /* cur_state */, 1 /* new state */);
318 } else {
319 // Failed to acquire, hang up.
320 ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
321 num_contenders_++;
322 if (futex(state_.Address(), FUTEX_WAIT, 1, NULL, NULL, 0) != 0) {
323 // EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
324 // We don't use TEMP_FAILURE_RETRY so we can intentionally retry to acquire the lock.
325 if ((errno != EAGAIN) && (errno != EINTR)) {
326 PLOG(FATAL) << "futex wait failed for " << name_;
327 }
328 }
329 num_contenders_--;
330 }
331 } while (!done);
332 DCHECK_EQ(state_.LoadRelaxed(), 1);
333 #else
334 CHECK_MUTEX_CALL(pthread_mutex_lock, (&mutex_));
335 #endif
336 DCHECK_EQ(exclusive_owner_, 0U);
337 exclusive_owner_ = SafeGetTid(self);
338 RegisterAsLocked(self);
339 }
340 recursion_count_++;
341 if (kDebugLocking) {
342 CHECK(recursion_count_ == 1 || recursive_) << "Unexpected recursion count on mutex: "
343 << name_ << " " << recursion_count_;
344 AssertHeld(self);
345 }
346 }
347
ExclusiveTryLock(Thread * self)348 bool Mutex::ExclusiveTryLock(Thread* self) {
349 DCHECK(self == NULL || self == Thread::Current());
350 if (kDebugLocking && !recursive_) {
351 AssertNotHeld(self);
352 }
353 if (!recursive_ || !IsExclusiveHeld(self)) {
354 #if ART_USE_FUTEXES
355 bool done = false;
356 do {
357 int32_t cur_state = state_.LoadRelaxed();
358 if (cur_state == 0) {
359 // Change state from 0 to 1 and impose load/store ordering appropriate for lock acquisition.
360 done = state_.CompareExchangeWeakAcquire(0 /* cur_state */, 1 /* new state */);
361 } else {
362 return false;
363 }
364 } while (!done);
365 DCHECK_EQ(state_.LoadRelaxed(), 1);
366 #else
367 int result = pthread_mutex_trylock(&mutex_);
368 if (result == EBUSY) {
369 return false;
370 }
371 if (result != 0) {
372 errno = result;
373 PLOG(FATAL) << "pthread_mutex_trylock failed for " << name_;
374 }
375 #endif
376 DCHECK_EQ(exclusive_owner_, 0U);
377 exclusive_owner_ = SafeGetTid(self);
378 RegisterAsLocked(self);
379 }
380 recursion_count_++;
381 if (kDebugLocking) {
382 CHECK(recursion_count_ == 1 || recursive_) << "Unexpected recursion count on mutex: "
383 << name_ << " " << recursion_count_;
384 AssertHeld(self);
385 }
386 return true;
387 }
388
ExclusiveUnlock(Thread * self)389 void Mutex::ExclusiveUnlock(Thread* self) {
390 DCHECK(self == NULL || self == Thread::Current());
391 AssertHeld(self);
392 DCHECK_NE(exclusive_owner_, 0U);
393 recursion_count_--;
394 if (!recursive_ || recursion_count_ == 0) {
395 if (kDebugLocking) {
396 CHECK(recursion_count_ == 0 || recursive_) << "Unexpected recursion count on mutex: "
397 << name_ << " " << recursion_count_;
398 }
399 RegisterAsUnlocked(self);
400 #if ART_USE_FUTEXES
401 bool done = false;
402 do {
403 int32_t cur_state = state_.LoadRelaxed();
404 if (LIKELY(cur_state == 1)) {
405 // We're no longer the owner.
406 exclusive_owner_ = 0;
407 // Change state to 0 and impose load/store ordering appropriate for lock release.
408 // Note, the relaxed loads below musn't reorder before the CompareExchange.
409 // TODO: the ordering here is non-trivial as state is split across 3 fields, fix by placing
410 // a status bit into the state on contention.
411 done = state_.CompareExchangeWeakSequentiallyConsistent(cur_state, 0 /* new state */);
412 if (LIKELY(done)) { // Spurious fail?
413 // Wake a contender.
414 if (UNLIKELY(num_contenders_.LoadRelaxed() > 0)) {
415 futex(state_.Address(), FUTEX_WAKE, 1, NULL, NULL, 0);
416 }
417 }
418 } else {
419 // Logging acquires the logging lock, avoid infinite recursion in that case.
420 if (this != Locks::logging_lock_) {
421 LOG(FATAL) << "Unexpected state_ in unlock " << cur_state << " for " << name_;
422 } else {
423 LogMessageData data(__FILE__, __LINE__, INTERNAL_FATAL, -1);
424 LogMessage::LogLine(data, StringPrintf("Unexpected state_ %d in unlock for %s",
425 cur_state, name_).c_str());
426 _exit(1);
427 }
428 }
429 } while (!done);
430 #else
431 exclusive_owner_ = 0;
432 CHECK_MUTEX_CALL(pthread_mutex_unlock, (&mutex_));
433 #endif
434 }
435 }
436
Dump(std::ostream & os) const437 void Mutex::Dump(std::ostream& os) const {
438 os << (recursive_ ? "recursive " : "non-recursive ")
439 << name_
440 << " level=" << static_cast<int>(level_)
441 << " rec=" << recursion_count_
442 << " owner=" << GetExclusiveOwnerTid() << " ";
443 DumpContention(os);
444 }
445
operator <<(std::ostream & os,const Mutex & mu)446 std::ostream& operator<<(std::ostream& os, const Mutex& mu) {
447 mu.Dump(os);
448 return os;
449 }
450
ReaderWriterMutex(const char * name,LockLevel level)451 ReaderWriterMutex::ReaderWriterMutex(const char* name, LockLevel level)
452 : BaseMutex(name, level)
453 #if ART_USE_FUTEXES
454 , state_(0), num_pending_readers_(0), num_pending_writers_(0)
455 #endif
456 { // NOLINT(whitespace/braces)
457 #if !ART_USE_FUTEXES
458 CHECK_MUTEX_CALL(pthread_rwlock_init, (&rwlock_, nullptr));
459 #endif
460 exclusive_owner_ = 0;
461 }
462
~ReaderWriterMutex()463 ReaderWriterMutex::~ReaderWriterMutex() {
464 #if ART_USE_FUTEXES
465 CHECK_EQ(state_.LoadRelaxed(), 0);
466 CHECK_EQ(exclusive_owner_, 0U);
467 CHECK_EQ(num_pending_readers_.LoadRelaxed(), 0);
468 CHECK_EQ(num_pending_writers_.LoadRelaxed(), 0);
469 #else
470 // We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
471 // may still be using locks.
472 int rc = pthread_rwlock_destroy(&rwlock_);
473 if (rc != 0) {
474 errno = rc;
475 // TODO: should we just not log at all if shutting down? this could be the logging mutex!
476 MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
477 Runtime* runtime = Runtime::Current();
478 bool shutting_down = runtime == NULL || runtime->IsShuttingDownLocked();
479 PLOG(shutting_down ? WARNING : FATAL) << "pthread_rwlock_destroy failed for " << name_;
480 }
481 #endif
482 }
483
ExclusiveLock(Thread * self)484 void ReaderWriterMutex::ExclusiveLock(Thread* self) {
485 DCHECK(self == NULL || self == Thread::Current());
486 AssertNotExclusiveHeld(self);
487 #if ART_USE_FUTEXES
488 bool done = false;
489 do {
490 int32_t cur_state = state_.LoadRelaxed();
491 if (LIKELY(cur_state == 0)) {
492 // Change state from 0 to -1 and impose load/store ordering appropriate for lock acquisition.
493 done = state_.CompareExchangeWeakAcquire(0 /* cur_state*/, -1 /* new state */);
494 } else {
495 // Failed to acquire, hang up.
496 ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
497 ++num_pending_writers_;
498 if (futex(state_.Address(), FUTEX_WAIT, cur_state, NULL, NULL, 0) != 0) {
499 // EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
500 // We don't use TEMP_FAILURE_RETRY so we can intentionally retry to acquire the lock.
501 if ((errno != EAGAIN) && (errno != EINTR)) {
502 PLOG(FATAL) << "futex wait failed for " << name_;
503 }
504 }
505 --num_pending_writers_;
506 }
507 } while (!done);
508 DCHECK_EQ(state_.LoadRelaxed(), -1);
509 #else
510 CHECK_MUTEX_CALL(pthread_rwlock_wrlock, (&rwlock_));
511 #endif
512 DCHECK_EQ(exclusive_owner_, 0U);
513 exclusive_owner_ = SafeGetTid(self);
514 RegisterAsLocked(self);
515 AssertExclusiveHeld(self);
516 }
517
ExclusiveUnlock(Thread * self)518 void ReaderWriterMutex::ExclusiveUnlock(Thread* self) {
519 DCHECK(self == NULL || self == Thread::Current());
520 AssertExclusiveHeld(self);
521 RegisterAsUnlocked(self);
522 DCHECK_NE(exclusive_owner_, 0U);
523 #if ART_USE_FUTEXES
524 bool done = false;
525 do {
526 int32_t cur_state = state_.LoadRelaxed();
527 if (LIKELY(cur_state == -1)) {
528 // We're no longer the owner.
529 exclusive_owner_ = 0;
530 // Change state from -1 to 0 and impose load/store ordering appropriate for lock release.
531 // Note, the relaxed loads below musn't reorder before the CompareExchange.
532 // TODO: the ordering here is non-trivial as state is split across 3 fields, fix by placing
533 // a status bit into the state on contention.
534 done = state_.CompareExchangeWeakSequentiallyConsistent(-1 /* cur_state*/, 0 /* new state */);
535 if (LIKELY(done)) { // Weak CAS may fail spuriously.
536 // Wake any waiters.
537 if (UNLIKELY(num_pending_readers_.LoadRelaxed() > 0 ||
538 num_pending_writers_.LoadRelaxed() > 0)) {
539 futex(state_.Address(), FUTEX_WAKE, -1, NULL, NULL, 0);
540 }
541 }
542 } else {
543 LOG(FATAL) << "Unexpected state_:" << cur_state << " for " << name_;
544 }
545 } while (!done);
546 #else
547 exclusive_owner_ = 0;
548 CHECK_MUTEX_CALL(pthread_rwlock_unlock, (&rwlock_));
549 #endif
550 }
551
552 #if HAVE_TIMED_RWLOCK
ExclusiveLockWithTimeout(Thread * self,int64_t ms,int32_t ns)553 bool ReaderWriterMutex::ExclusiveLockWithTimeout(Thread* self, int64_t ms, int32_t ns) {
554 DCHECK(self == NULL || self == Thread::Current());
555 #if ART_USE_FUTEXES
556 bool done = false;
557 timespec end_abs_ts;
558 InitTimeSpec(true, CLOCK_REALTIME, ms, ns, &end_abs_ts);
559 do {
560 int32_t cur_state = state_.LoadRelaxed();
561 if (cur_state == 0) {
562 // Change state from 0 to -1 and impose load/store ordering appropriate for lock acquisition.
563 done = state_.CompareExchangeWeakAcquire(0 /* cur_state */, -1 /* new state */);
564 } else {
565 // Failed to acquire, hang up.
566 timespec now_abs_ts;
567 InitTimeSpec(true, CLOCK_REALTIME, 0, 0, &now_abs_ts);
568 timespec rel_ts;
569 if (ComputeRelativeTimeSpec(&rel_ts, end_abs_ts, now_abs_ts)) {
570 return false; // Timed out.
571 }
572 ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
573 ++num_pending_writers_;
574 if (futex(state_.Address(), FUTEX_WAIT, cur_state, &rel_ts, NULL, 0) != 0) {
575 if (errno == ETIMEDOUT) {
576 --num_pending_writers_;
577 return false; // Timed out.
578 } else if ((errno != EAGAIN) && (errno != EINTR)) {
579 // EAGAIN and EINTR both indicate a spurious failure,
580 // recompute the relative time out from now and try again.
581 // We don't use TEMP_FAILURE_RETRY so we can recompute rel_ts;
582 PLOG(FATAL) << "timed futex wait failed for " << name_;
583 }
584 }
585 --num_pending_writers_;
586 }
587 } while (!done);
588 #else
589 timespec ts;
590 InitTimeSpec(true, CLOCK_REALTIME, ms, ns, &ts);
591 int result = pthread_rwlock_timedwrlock(&rwlock_, &ts);
592 if (result == ETIMEDOUT) {
593 return false;
594 }
595 if (result != 0) {
596 errno = result;
597 PLOG(FATAL) << "pthread_rwlock_timedwrlock failed for " << name_;
598 }
599 #endif
600 exclusive_owner_ = SafeGetTid(self);
601 RegisterAsLocked(self);
602 AssertSharedHeld(self);
603 return true;
604 }
605 #endif
606
SharedTryLock(Thread * self)607 bool ReaderWriterMutex::SharedTryLock(Thread* self) {
608 DCHECK(self == NULL || self == Thread::Current());
609 #if ART_USE_FUTEXES
610 bool done = false;
611 do {
612 int32_t cur_state = state_.LoadRelaxed();
613 if (cur_state >= 0) {
614 // Add as an extra reader and impose load/store ordering appropriate for lock acquisition.
615 done = state_.CompareExchangeWeakAcquire(cur_state, cur_state + 1);
616 } else {
617 // Owner holds it exclusively.
618 return false;
619 }
620 } while (!done);
621 #else
622 int result = pthread_rwlock_tryrdlock(&rwlock_);
623 if (result == EBUSY) {
624 return false;
625 }
626 if (result != 0) {
627 errno = result;
628 PLOG(FATAL) << "pthread_mutex_trylock failed for " << name_;
629 }
630 #endif
631 RegisterAsLocked(self);
632 AssertSharedHeld(self);
633 return true;
634 }
635
IsSharedHeld(const Thread * self) const636 bool ReaderWriterMutex::IsSharedHeld(const Thread* self) const {
637 DCHECK(self == NULL || self == Thread::Current());
638 bool result;
639 if (UNLIKELY(self == NULL)) { // Handle unattached threads.
640 result = IsExclusiveHeld(self); // TODO: a better best effort here.
641 } else {
642 result = (self->GetHeldMutex(level_) == this);
643 }
644 return result;
645 }
646
Dump(std::ostream & os) const647 void ReaderWriterMutex::Dump(std::ostream& os) const {
648 os << name_
649 << " level=" << static_cast<int>(level_)
650 << " owner=" << GetExclusiveOwnerTid() << " ";
651 DumpContention(os);
652 }
653
operator <<(std::ostream & os,const ReaderWriterMutex & mu)654 std::ostream& operator<<(std::ostream& os, const ReaderWriterMutex& mu) {
655 mu.Dump(os);
656 return os;
657 }
658
ConditionVariable(const char * name,Mutex & guard)659 ConditionVariable::ConditionVariable(const char* name, Mutex& guard)
660 : name_(name), guard_(guard) {
661 #if ART_USE_FUTEXES
662 DCHECK_EQ(0, sequence_.LoadRelaxed());
663 num_waiters_ = 0;
664 #else
665 pthread_condattr_t cond_attrs;
666 CHECK_MUTEX_CALL(pthread_condattr_init, (&cond_attrs));
667 #if !defined(__APPLE__)
668 // Apple doesn't have CLOCK_MONOTONIC or pthread_condattr_setclock.
669 CHECK_MUTEX_CALL(pthread_condattr_setclock(&cond_attrs, CLOCK_MONOTONIC));
670 #endif
671 CHECK_MUTEX_CALL(pthread_cond_init, (&cond_, &cond_attrs));
672 #endif
673 }
674
~ConditionVariable()675 ConditionVariable::~ConditionVariable() {
676 #if ART_USE_FUTEXES
677 if (num_waiters_!= 0) {
678 Runtime* runtime = Runtime::Current();
679 bool shutting_down = runtime == nullptr || runtime->IsShuttingDown(Thread::Current());
680 LOG(shutting_down ? WARNING : FATAL) << "ConditionVariable::~ConditionVariable for " << name_
681 << " called with " << num_waiters_ << " waiters.";
682 }
683 #else
684 // We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
685 // may still be using condition variables.
686 int rc = pthread_cond_destroy(&cond_);
687 if (rc != 0) {
688 errno = rc;
689 MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
690 Runtime* runtime = Runtime::Current();
691 bool shutting_down = (runtime == NULL) || runtime->IsShuttingDownLocked();
692 PLOG(shutting_down ? WARNING : FATAL) << "pthread_cond_destroy failed for " << name_;
693 }
694 #endif
695 }
696
Broadcast(Thread * self)697 void ConditionVariable::Broadcast(Thread* self) {
698 DCHECK(self == NULL || self == Thread::Current());
699 // TODO: enable below, there's a race in thread creation that causes false failures currently.
700 // guard_.AssertExclusiveHeld(self);
701 DCHECK_EQ(guard_.GetExclusiveOwnerTid(), SafeGetTid(self));
702 #if ART_USE_FUTEXES
703 if (num_waiters_ > 0) {
704 sequence_++; // Indicate the broadcast occurred.
705 bool done = false;
706 do {
707 int32_t cur_sequence = sequence_.LoadRelaxed();
708 // Requeue waiters onto mutex. The waiter holds the contender count on the mutex high ensuring
709 // mutex unlocks will awaken the requeued waiter thread.
710 done = futex(sequence_.Address(), FUTEX_CMP_REQUEUE, 0,
711 reinterpret_cast<const timespec*>(std::numeric_limits<int32_t>::max()),
712 guard_.state_.Address(), cur_sequence) != -1;
713 if (!done) {
714 if (errno != EAGAIN) {
715 PLOG(FATAL) << "futex cmp requeue failed for " << name_;
716 }
717 }
718 } while (!done);
719 }
720 #else
721 CHECK_MUTEX_CALL(pthread_cond_broadcast, (&cond_));
722 #endif
723 }
724
Signal(Thread * self)725 void ConditionVariable::Signal(Thread* self) {
726 DCHECK(self == NULL || self == Thread::Current());
727 guard_.AssertExclusiveHeld(self);
728 #if ART_USE_FUTEXES
729 if (num_waiters_ > 0) {
730 sequence_++; // Indicate a signal occurred.
731 // Futex wake 1 waiter who will then come and in contend on mutex. It'd be nice to requeue them
732 // to avoid this, however, requeueing can only move all waiters.
733 int num_woken = futex(sequence_.Address(), FUTEX_WAKE, 1, NULL, NULL, 0);
734 // Check something was woken or else we changed sequence_ before they had chance to wait.
735 CHECK((num_woken == 0) || (num_woken == 1));
736 }
737 #else
738 CHECK_MUTEX_CALL(pthread_cond_signal, (&cond_));
739 #endif
740 }
741
Wait(Thread * self)742 void ConditionVariable::Wait(Thread* self) {
743 guard_.CheckSafeToWait(self);
744 WaitHoldingLocks(self);
745 }
746
WaitHoldingLocks(Thread * self)747 void ConditionVariable::WaitHoldingLocks(Thread* self) {
748 DCHECK(self == NULL || self == Thread::Current());
749 guard_.AssertExclusiveHeld(self);
750 unsigned int old_recursion_count = guard_.recursion_count_;
751 #if ART_USE_FUTEXES
752 num_waiters_++;
753 // Ensure the Mutex is contended so that requeued threads are awoken.
754 guard_.num_contenders_++;
755 guard_.recursion_count_ = 1;
756 int32_t cur_sequence = sequence_.LoadRelaxed();
757 guard_.ExclusiveUnlock(self);
758 if (futex(sequence_.Address(), FUTEX_WAIT, cur_sequence, NULL, NULL, 0) != 0) {
759 // Futex failed, check it is an expected error.
760 // EAGAIN == EWOULDBLK, so we let the caller try again.
761 // EINTR implies a signal was sent to this thread.
762 if ((errno != EINTR) && (errno != EAGAIN)) {
763 PLOG(FATAL) << "futex wait failed for " << name_;
764 }
765 }
766 guard_.ExclusiveLock(self);
767 CHECK_GE(num_waiters_, 0);
768 num_waiters_--;
769 // We awoke and so no longer require awakes from the guard_'s unlock.
770 CHECK_GE(guard_.num_contenders_.LoadRelaxed(), 0);
771 guard_.num_contenders_--;
772 #else
773 uint64_t old_owner = guard_.exclusive_owner_;
774 guard_.exclusive_owner_ = 0;
775 guard_.recursion_count_ = 0;
776 CHECK_MUTEX_CALL(pthread_cond_wait, (&cond_, &guard_.mutex_));
777 guard_.exclusive_owner_ = old_owner;
778 #endif
779 guard_.recursion_count_ = old_recursion_count;
780 }
781
TimedWait(Thread * self,int64_t ms,int32_t ns)782 void ConditionVariable::TimedWait(Thread* self, int64_t ms, int32_t ns) {
783 DCHECK(self == NULL || self == Thread::Current());
784 guard_.AssertExclusiveHeld(self);
785 guard_.CheckSafeToWait(self);
786 unsigned int old_recursion_count = guard_.recursion_count_;
787 #if ART_USE_FUTEXES
788 timespec rel_ts;
789 InitTimeSpec(false, CLOCK_REALTIME, ms, ns, &rel_ts);
790 num_waiters_++;
791 // Ensure the Mutex is contended so that requeued threads are awoken.
792 guard_.num_contenders_++;
793 guard_.recursion_count_ = 1;
794 int32_t cur_sequence = sequence_.LoadRelaxed();
795 guard_.ExclusiveUnlock(self);
796 if (futex(sequence_.Address(), FUTEX_WAIT, cur_sequence, &rel_ts, NULL, 0) != 0) {
797 if (errno == ETIMEDOUT) {
798 // Timed out we're done.
799 } else if ((errno == EAGAIN) || (errno == EINTR)) {
800 // A signal or ConditionVariable::Signal/Broadcast has come in.
801 } else {
802 PLOG(FATAL) << "timed futex wait failed for " << name_;
803 }
804 }
805 guard_.ExclusiveLock(self);
806 CHECK_GE(num_waiters_, 0);
807 num_waiters_--;
808 // We awoke and so no longer require awakes from the guard_'s unlock.
809 CHECK_GE(guard_.num_contenders_.LoadRelaxed(), 0);
810 guard_.num_contenders_--;
811 #else
812 #if !defined(__APPLE__)
813 int clock = CLOCK_MONOTONIC;
814 #else
815 int clock = CLOCK_REALTIME;
816 #endif
817 uint64_t old_owner = guard_.exclusive_owner_;
818 guard_.exclusive_owner_ = 0;
819 guard_.recursion_count_ = 0;
820 timespec ts;
821 InitTimeSpec(true, clock, ms, ns, &ts);
822 int rc = TEMP_FAILURE_RETRY(pthread_cond_timedwait(&cond_, &guard_.mutex_, &ts));
823 if (rc != 0 && rc != ETIMEDOUT) {
824 errno = rc;
825 PLOG(FATAL) << "TimedWait failed for " << name_;
826 }
827 guard_.exclusive_owner_ = old_owner;
828 #endif
829 guard_.recursion_count_ = old_recursion_count;
830 }
831
Init()832 void Locks::Init() {
833 if (logging_lock_ != nullptr) {
834 // Already initialized.
835 if (kRuntimeISA == kX86 || kRuntimeISA == kX86_64) {
836 DCHECK(modify_ldt_lock_ != nullptr);
837 } else {
838 DCHECK(modify_ldt_lock_ == nullptr);
839 }
840 DCHECK(abort_lock_ != nullptr);
841 DCHECK(alloc_tracker_lock_ != nullptr);
842 DCHECK(allocated_monitor_ids_lock_ != nullptr);
843 DCHECK(allocated_thread_ids_lock_ != nullptr);
844 DCHECK(breakpoint_lock_ != nullptr);
845 DCHECK(classlinker_classes_lock_ != nullptr);
846 DCHECK(deoptimization_lock_ != nullptr);
847 DCHECK(heap_bitmap_lock_ != nullptr);
848 DCHECK(intern_table_lock_ != nullptr);
849 DCHECK(logging_lock_ != nullptr);
850 DCHECK(mutator_lock_ != nullptr);
851 DCHECK(profiler_lock_ != nullptr);
852 DCHECK(thread_list_lock_ != nullptr);
853 DCHECK(thread_list_suspend_thread_lock_ != nullptr);
854 DCHECK(thread_suspend_count_lock_ != nullptr);
855 DCHECK(trace_lock_ != nullptr);
856 DCHECK(unexpected_signal_lock_ != nullptr);
857 } else {
858 // Create global locks in level order from highest lock level to lowest.
859 LockLevel current_lock_level = kThreadListSuspendThreadLock;
860 DCHECK(thread_list_suspend_thread_lock_ == nullptr);
861 thread_list_suspend_thread_lock_ =
862 new Mutex("thread list suspend thread by .. lock", current_lock_level);
863
864 #define UPDATE_CURRENT_LOCK_LEVEL(new_level) \
865 if (new_level >= current_lock_level) { \
866 /* Do not use CHECKs or FATAL here, abort_lock_ is not setup yet. */ \
867 fprintf(stderr, "New local level %d is not less than current level %d\n", \
868 new_level, current_lock_level); \
869 exit(1); \
870 } \
871 current_lock_level = new_level;
872
873 UPDATE_CURRENT_LOCK_LEVEL(kInstrumentEntrypointsLock);
874 DCHECK(instrument_entrypoints_lock_ == nullptr);
875 instrument_entrypoints_lock_ = new Mutex("instrument entrypoint lock", current_lock_level);
876
877 UPDATE_CURRENT_LOCK_LEVEL(kMutatorLock);
878 DCHECK(mutator_lock_ == nullptr);
879 mutator_lock_ = new ReaderWriterMutex("mutator lock", current_lock_level);
880
881 UPDATE_CURRENT_LOCK_LEVEL(kHeapBitmapLock);
882 DCHECK(heap_bitmap_lock_ == nullptr);
883 heap_bitmap_lock_ = new ReaderWriterMutex("heap bitmap lock", current_lock_level);
884
885 UPDATE_CURRENT_LOCK_LEVEL(kTraceLock);
886 DCHECK(trace_lock_ == nullptr);
887 trace_lock_ = new Mutex("trace lock", current_lock_level);
888
889 UPDATE_CURRENT_LOCK_LEVEL(kRuntimeShutdownLock);
890 DCHECK(runtime_shutdown_lock_ == nullptr);
891 runtime_shutdown_lock_ = new Mutex("runtime shutdown lock", current_lock_level);
892
893 UPDATE_CURRENT_LOCK_LEVEL(kProfilerLock);
894 DCHECK(profiler_lock_ == nullptr);
895 profiler_lock_ = new Mutex("profiler lock", current_lock_level);
896
897 UPDATE_CURRENT_LOCK_LEVEL(kDeoptimizationLock);
898 DCHECK(deoptimization_lock_ == nullptr);
899 deoptimization_lock_ = new Mutex("Deoptimization lock", current_lock_level);
900
901 UPDATE_CURRENT_LOCK_LEVEL(kAllocTrackerLock);
902 DCHECK(alloc_tracker_lock_ == nullptr);
903 alloc_tracker_lock_ = new Mutex("AllocTracker lock", current_lock_level);
904
905 UPDATE_CURRENT_LOCK_LEVEL(kThreadListLock);
906 DCHECK(thread_list_lock_ == nullptr);
907 thread_list_lock_ = new Mutex("thread list lock", current_lock_level);
908
909 UPDATE_CURRENT_LOCK_LEVEL(kBreakpointLock);
910 DCHECK(breakpoint_lock_ == nullptr);
911 breakpoint_lock_ = new ReaderWriterMutex("breakpoint lock", current_lock_level);
912
913 UPDATE_CURRENT_LOCK_LEVEL(kClassLinkerClassesLock);
914 DCHECK(classlinker_classes_lock_ == nullptr);
915 classlinker_classes_lock_ = new ReaderWriterMutex("ClassLinker classes lock",
916 current_lock_level);
917
918 UPDATE_CURRENT_LOCK_LEVEL(kMonitorPoolLock);
919 DCHECK(allocated_monitor_ids_lock_ == nullptr);
920 allocated_monitor_ids_lock_ = new Mutex("allocated monitor ids lock", current_lock_level);
921
922 UPDATE_CURRENT_LOCK_LEVEL(kAllocatedThreadIdsLock);
923 DCHECK(allocated_thread_ids_lock_ == nullptr);
924 allocated_thread_ids_lock_ = new Mutex("allocated thread ids lock", current_lock_level);
925
926 if (kRuntimeISA == kX86 || kRuntimeISA == kX86_64) {
927 UPDATE_CURRENT_LOCK_LEVEL(kModifyLdtLock);
928 DCHECK(modify_ldt_lock_ == nullptr);
929 modify_ldt_lock_ = new Mutex("modify_ldt lock", current_lock_level);
930 }
931
932 UPDATE_CURRENT_LOCK_LEVEL(kInternTableLock);
933 DCHECK(intern_table_lock_ == nullptr);
934 intern_table_lock_ = new Mutex("InternTable lock", current_lock_level);
935
936 UPDATE_CURRENT_LOCK_LEVEL(kReferenceProcessorLock);
937 DCHECK(reference_processor_lock_ == nullptr);
938 reference_processor_lock_ = new Mutex("ReferenceProcessor lock", current_lock_level);
939
940 UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueClearedReferencesLock);
941 DCHECK(reference_queue_cleared_references_lock_ == nullptr);
942 reference_queue_cleared_references_lock_ = new Mutex("ReferenceQueue cleared references lock", current_lock_level);
943
944 UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueWeakReferencesLock);
945 DCHECK(reference_queue_weak_references_lock_ == nullptr);
946 reference_queue_weak_references_lock_ = new Mutex("ReferenceQueue cleared references lock", current_lock_level);
947
948 UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueFinalizerReferencesLock);
949 DCHECK(reference_queue_finalizer_references_lock_ == nullptr);
950 reference_queue_finalizer_references_lock_ = new Mutex("ReferenceQueue finalizer references lock", current_lock_level);
951
952 UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueuePhantomReferencesLock);
953 DCHECK(reference_queue_phantom_references_lock_ == nullptr);
954 reference_queue_phantom_references_lock_ = new Mutex("ReferenceQueue phantom references lock", current_lock_level);
955
956 UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueSoftReferencesLock);
957 DCHECK(reference_queue_soft_references_lock_ == nullptr);
958 reference_queue_soft_references_lock_ = new Mutex("ReferenceQueue soft references lock", current_lock_level);
959
960 UPDATE_CURRENT_LOCK_LEVEL(kAbortLock);
961 DCHECK(abort_lock_ == nullptr);
962 abort_lock_ = new Mutex("abort lock", current_lock_level, true);
963
964 UPDATE_CURRENT_LOCK_LEVEL(kThreadSuspendCountLock);
965 DCHECK(thread_suspend_count_lock_ == nullptr);
966 thread_suspend_count_lock_ = new Mutex("thread suspend count lock", current_lock_level);
967
968 UPDATE_CURRENT_LOCK_LEVEL(kUnexpectedSignalLock);
969 DCHECK(unexpected_signal_lock_ == nullptr);
970 unexpected_signal_lock_ = new Mutex("unexpected signal lock", current_lock_level, true);
971
972 UPDATE_CURRENT_LOCK_LEVEL(kMemMapsLock);
973 DCHECK(mem_maps_lock_ == nullptr);
974 mem_maps_lock_ = new Mutex("mem maps lock", current_lock_level);
975
976 UPDATE_CURRENT_LOCK_LEVEL(kLoggingLock);
977 DCHECK(logging_lock_ == nullptr);
978 logging_lock_ = new Mutex("logging lock", current_lock_level, true);
979
980 #undef UPDATE_CURRENT_LOCK_LEVEL
981 }
982 }
983
984
985 } // namespace art
986