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
279 // Helper to ignore the lock requirement.
IsShuttingDown()280 static bool IsShuttingDown() NO_THREAD_SAFETY_ANALYSIS {
281 Runtime* runtime = Runtime::Current();
282 return runtime == nullptr || runtime->IsShuttingDownLocked();
283 }
284
~Mutex()285 Mutex::~Mutex() {
286 bool shutting_down = IsShuttingDown();
287 #if ART_USE_FUTEXES
288 if (state_.LoadRelaxed() != 0) {
289 LOG(shutting_down ? WARNING : FATAL) << "destroying mutex with owner: "
290 << exclusive_owner_;
291 } else {
292 if (exclusive_owner_ != 0) {
293 LOG(shutting_down ? WARNING : FATAL) << "unexpectedly found an owner on unlocked mutex "
294 << name_;
295 }
296 if (num_contenders_.LoadSequentiallyConsistent() != 0) {
297 LOG(shutting_down ? WARNING : FATAL) << "unexpectedly found a contender on mutex " << name_;
298 }
299 }
300 #else
301 // We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
302 // may still be using locks.
303 int rc = pthread_mutex_destroy(&mutex_);
304 if (rc != 0) {
305 errno = rc;
306 // TODO: should we just not log at all if shutting down? this could be the logging mutex!
307 MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
308 PLOG(shutting_down ? WARNING : FATAL) << "pthread_mutex_destroy failed for " << name_;
309 }
310 #endif
311 }
312
ExclusiveLock(Thread * self)313 void Mutex::ExclusiveLock(Thread* self) {
314 DCHECK(self == NULL || self == Thread::Current());
315 if (kDebugLocking && !recursive_) {
316 AssertNotHeld(self);
317 }
318 if (!recursive_ || !IsExclusiveHeld(self)) {
319 #if ART_USE_FUTEXES
320 bool done = false;
321 do {
322 int32_t cur_state = state_.LoadRelaxed();
323 if (LIKELY(cur_state == 0)) {
324 // Change state from 0 to 1 and impose load/store ordering appropriate for lock acquisition.
325 done = state_.CompareExchangeWeakAcquire(0 /* cur_state */, 1 /* new state */);
326 } else {
327 // Failed to acquire, hang up.
328 ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
329 num_contenders_++;
330 if (futex(state_.Address(), FUTEX_WAIT, 1, NULL, NULL, 0) != 0) {
331 // EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
332 // We don't use TEMP_FAILURE_RETRY so we can intentionally retry to acquire the lock.
333 if ((errno != EAGAIN) && (errno != EINTR)) {
334 PLOG(FATAL) << "futex wait failed for " << name_;
335 }
336 }
337 num_contenders_--;
338 }
339 } while (!done);
340 DCHECK_EQ(state_.LoadRelaxed(), 1);
341 #else
342 CHECK_MUTEX_CALL(pthread_mutex_lock, (&mutex_));
343 #endif
344 DCHECK_EQ(exclusive_owner_, 0U);
345 exclusive_owner_ = SafeGetTid(self);
346 RegisterAsLocked(self);
347 }
348 recursion_count_++;
349 if (kDebugLocking) {
350 CHECK(recursion_count_ == 1 || recursive_) << "Unexpected recursion count on mutex: "
351 << name_ << " " << recursion_count_;
352 AssertHeld(self);
353 }
354 }
355
ExclusiveTryLock(Thread * self)356 bool Mutex::ExclusiveTryLock(Thread* self) {
357 DCHECK(self == NULL || self == Thread::Current());
358 if (kDebugLocking && !recursive_) {
359 AssertNotHeld(self);
360 }
361 if (!recursive_ || !IsExclusiveHeld(self)) {
362 #if ART_USE_FUTEXES
363 bool done = false;
364 do {
365 int32_t cur_state = state_.LoadRelaxed();
366 if (cur_state == 0) {
367 // Change state from 0 to 1 and impose load/store ordering appropriate for lock acquisition.
368 done = state_.CompareExchangeWeakAcquire(0 /* cur_state */, 1 /* new state */);
369 } else {
370 return false;
371 }
372 } while (!done);
373 DCHECK_EQ(state_.LoadRelaxed(), 1);
374 #else
375 int result = pthread_mutex_trylock(&mutex_);
376 if (result == EBUSY) {
377 return false;
378 }
379 if (result != 0) {
380 errno = result;
381 PLOG(FATAL) << "pthread_mutex_trylock failed for " << name_;
382 }
383 #endif
384 DCHECK_EQ(exclusive_owner_, 0U);
385 exclusive_owner_ = SafeGetTid(self);
386 RegisterAsLocked(self);
387 }
388 recursion_count_++;
389 if (kDebugLocking) {
390 CHECK(recursion_count_ == 1 || recursive_) << "Unexpected recursion count on mutex: "
391 << name_ << " " << recursion_count_;
392 AssertHeld(self);
393 }
394 return true;
395 }
396
ExclusiveUnlock(Thread * self)397 void Mutex::ExclusiveUnlock(Thread* self) {
398 DCHECK(self == NULL || self == Thread::Current());
399 AssertHeld(self);
400 DCHECK_NE(exclusive_owner_, 0U);
401 recursion_count_--;
402 if (!recursive_ || recursion_count_ == 0) {
403 if (kDebugLocking) {
404 CHECK(recursion_count_ == 0 || recursive_) << "Unexpected recursion count on mutex: "
405 << name_ << " " << recursion_count_;
406 }
407 RegisterAsUnlocked(self);
408 #if ART_USE_FUTEXES
409 bool done = false;
410 do {
411 int32_t cur_state = state_.LoadRelaxed();
412 if (LIKELY(cur_state == 1)) {
413 // We're no longer the owner.
414 exclusive_owner_ = 0;
415 // Change state to 0 and impose load/store ordering appropriate for lock release.
416 // Note, the relaxed loads below musn't reorder before the CompareExchange.
417 // TODO: the ordering here is non-trivial as state is split across 3 fields, fix by placing
418 // a status bit into the state on contention.
419 done = state_.CompareExchangeWeakSequentiallyConsistent(cur_state, 0 /* new state */);
420 if (LIKELY(done)) { // Spurious fail?
421 // Wake a contender.
422 if (UNLIKELY(num_contenders_.LoadRelaxed() > 0)) {
423 futex(state_.Address(), FUTEX_WAKE, 1, NULL, NULL, 0);
424 }
425 }
426 } else {
427 // Logging acquires the logging lock, avoid infinite recursion in that case.
428 if (this != Locks::logging_lock_) {
429 LOG(FATAL) << "Unexpected state_ in unlock " << cur_state << " for " << name_;
430 } else {
431 LogMessageData data(__FILE__, __LINE__, INTERNAL_FATAL, -1);
432 LogMessage::LogLine(data, StringPrintf("Unexpected state_ %d in unlock for %s",
433 cur_state, name_).c_str());
434 _exit(1);
435 }
436 }
437 } while (!done);
438 #else
439 exclusive_owner_ = 0;
440 CHECK_MUTEX_CALL(pthread_mutex_unlock, (&mutex_));
441 #endif
442 }
443 }
444
Dump(std::ostream & os) const445 void Mutex::Dump(std::ostream& os) const {
446 os << (recursive_ ? "recursive " : "non-recursive ")
447 << name_
448 << " level=" << static_cast<int>(level_)
449 << " rec=" << recursion_count_
450 << " owner=" << GetExclusiveOwnerTid() << " ";
451 DumpContention(os);
452 }
453
operator <<(std::ostream & os,const Mutex & mu)454 std::ostream& operator<<(std::ostream& os, const Mutex& mu) {
455 mu.Dump(os);
456 return os;
457 }
458
ReaderWriterMutex(const char * name,LockLevel level)459 ReaderWriterMutex::ReaderWriterMutex(const char* name, LockLevel level)
460 : BaseMutex(name, level)
461 #if ART_USE_FUTEXES
462 , state_(0), num_pending_readers_(0), num_pending_writers_(0)
463 #endif
464 { // NOLINT(whitespace/braces)
465 #if !ART_USE_FUTEXES
466 CHECK_MUTEX_CALL(pthread_rwlock_init, (&rwlock_, nullptr));
467 #endif
468 exclusive_owner_ = 0;
469 }
470
~ReaderWriterMutex()471 ReaderWriterMutex::~ReaderWriterMutex() {
472 #if ART_USE_FUTEXES
473 CHECK_EQ(state_.LoadRelaxed(), 0);
474 CHECK_EQ(exclusive_owner_, 0U);
475 CHECK_EQ(num_pending_readers_.LoadRelaxed(), 0);
476 CHECK_EQ(num_pending_writers_.LoadRelaxed(), 0);
477 #else
478 // We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
479 // may still be using locks.
480 int rc = pthread_rwlock_destroy(&rwlock_);
481 if (rc != 0) {
482 errno = rc;
483 // TODO: should we just not log at all if shutting down? this could be the logging mutex!
484 MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
485 Runtime* runtime = Runtime::Current();
486 bool shutting_down = runtime == NULL || runtime->IsShuttingDownLocked();
487 PLOG(shutting_down ? WARNING : FATAL) << "pthread_rwlock_destroy failed for " << name_;
488 }
489 #endif
490 }
491
ExclusiveLock(Thread * self)492 void ReaderWriterMutex::ExclusiveLock(Thread* self) {
493 DCHECK(self == NULL || self == Thread::Current());
494 AssertNotExclusiveHeld(self);
495 #if ART_USE_FUTEXES
496 bool done = false;
497 do {
498 int32_t cur_state = state_.LoadRelaxed();
499 if (LIKELY(cur_state == 0)) {
500 // Change state from 0 to -1 and impose load/store ordering appropriate for lock acquisition.
501 done = state_.CompareExchangeWeakAcquire(0 /* cur_state*/, -1 /* new state */);
502 } else {
503 // Failed to acquire, hang up.
504 ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
505 ++num_pending_writers_;
506 if (futex(state_.Address(), FUTEX_WAIT, cur_state, NULL, NULL, 0) != 0) {
507 // EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
508 // We don't use TEMP_FAILURE_RETRY so we can intentionally retry to acquire the lock.
509 if ((errno != EAGAIN) && (errno != EINTR)) {
510 PLOG(FATAL) << "futex wait failed for " << name_;
511 }
512 }
513 --num_pending_writers_;
514 }
515 } while (!done);
516 DCHECK_EQ(state_.LoadRelaxed(), -1);
517 #else
518 CHECK_MUTEX_CALL(pthread_rwlock_wrlock, (&rwlock_));
519 #endif
520 DCHECK_EQ(exclusive_owner_, 0U);
521 exclusive_owner_ = SafeGetTid(self);
522 RegisterAsLocked(self);
523 AssertExclusiveHeld(self);
524 }
525
ExclusiveUnlock(Thread * self)526 void ReaderWriterMutex::ExclusiveUnlock(Thread* self) {
527 DCHECK(self == NULL || self == Thread::Current());
528 AssertExclusiveHeld(self);
529 RegisterAsUnlocked(self);
530 DCHECK_NE(exclusive_owner_, 0U);
531 #if ART_USE_FUTEXES
532 bool done = false;
533 do {
534 int32_t cur_state = state_.LoadRelaxed();
535 if (LIKELY(cur_state == -1)) {
536 // We're no longer the owner.
537 exclusive_owner_ = 0;
538 // Change state from -1 to 0 and impose load/store ordering appropriate for lock release.
539 // Note, the relaxed loads below musn't reorder before the CompareExchange.
540 // TODO: the ordering here is non-trivial as state is split across 3 fields, fix by placing
541 // a status bit into the state on contention.
542 done = state_.CompareExchangeWeakSequentiallyConsistent(-1 /* cur_state*/, 0 /* new state */);
543 if (LIKELY(done)) { // Weak CAS may fail spuriously.
544 // Wake any waiters.
545 if (UNLIKELY(num_pending_readers_.LoadRelaxed() > 0 ||
546 num_pending_writers_.LoadRelaxed() > 0)) {
547 futex(state_.Address(), FUTEX_WAKE, -1, NULL, NULL, 0);
548 }
549 }
550 } else {
551 LOG(FATAL) << "Unexpected state_:" << cur_state << " for " << name_;
552 }
553 } while (!done);
554 #else
555 exclusive_owner_ = 0;
556 CHECK_MUTEX_CALL(pthread_rwlock_unlock, (&rwlock_));
557 #endif
558 }
559
560 #if HAVE_TIMED_RWLOCK
ExclusiveLockWithTimeout(Thread * self,int64_t ms,int32_t ns)561 bool ReaderWriterMutex::ExclusiveLockWithTimeout(Thread* self, int64_t ms, int32_t ns) {
562 DCHECK(self == NULL || self == Thread::Current());
563 #if ART_USE_FUTEXES
564 bool done = false;
565 timespec end_abs_ts;
566 InitTimeSpec(true, CLOCK_MONOTONIC, ms, ns, &end_abs_ts);
567 do {
568 int32_t cur_state = state_.LoadRelaxed();
569 if (cur_state == 0) {
570 // Change state from 0 to -1 and impose load/store ordering appropriate for lock acquisition.
571 done = state_.CompareExchangeWeakAcquire(0 /* cur_state */, -1 /* new state */);
572 } else {
573 // Failed to acquire, hang up.
574 timespec now_abs_ts;
575 InitTimeSpec(true, CLOCK_MONOTONIC, 0, 0, &now_abs_ts);
576 timespec rel_ts;
577 if (ComputeRelativeTimeSpec(&rel_ts, end_abs_ts, now_abs_ts)) {
578 return false; // Timed out.
579 }
580 ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
581 ++num_pending_writers_;
582 if (futex(state_.Address(), FUTEX_WAIT, cur_state, &rel_ts, NULL, 0) != 0) {
583 if (errno == ETIMEDOUT) {
584 --num_pending_writers_;
585 return false; // Timed out.
586 } else if ((errno != EAGAIN) && (errno != EINTR)) {
587 // EAGAIN and EINTR both indicate a spurious failure,
588 // recompute the relative time out from now and try again.
589 // We don't use TEMP_FAILURE_RETRY so we can recompute rel_ts;
590 PLOG(FATAL) << "timed futex wait failed for " << name_;
591 }
592 }
593 --num_pending_writers_;
594 }
595 } while (!done);
596 #else
597 timespec ts;
598 InitTimeSpec(true, CLOCK_REALTIME, ms, ns, &ts);
599 int result = pthread_rwlock_timedwrlock(&rwlock_, &ts);
600 if (result == ETIMEDOUT) {
601 return false;
602 }
603 if (result != 0) {
604 errno = result;
605 PLOG(FATAL) << "pthread_rwlock_timedwrlock failed for " << name_;
606 }
607 #endif
608 exclusive_owner_ = SafeGetTid(self);
609 RegisterAsLocked(self);
610 AssertSharedHeld(self);
611 return true;
612 }
613 #endif
614
SharedTryLock(Thread * self)615 bool ReaderWriterMutex::SharedTryLock(Thread* self) {
616 DCHECK(self == NULL || self == Thread::Current());
617 #if ART_USE_FUTEXES
618 bool done = false;
619 do {
620 int32_t cur_state = state_.LoadRelaxed();
621 if (cur_state >= 0) {
622 // Add as an extra reader and impose load/store ordering appropriate for lock acquisition.
623 done = state_.CompareExchangeWeakAcquire(cur_state, cur_state + 1);
624 } else {
625 // Owner holds it exclusively.
626 return false;
627 }
628 } while (!done);
629 #else
630 int result = pthread_rwlock_tryrdlock(&rwlock_);
631 if (result == EBUSY) {
632 return false;
633 }
634 if (result != 0) {
635 errno = result;
636 PLOG(FATAL) << "pthread_mutex_trylock failed for " << name_;
637 }
638 #endif
639 RegisterAsLocked(self);
640 AssertSharedHeld(self);
641 return true;
642 }
643
IsSharedHeld(const Thread * self) const644 bool ReaderWriterMutex::IsSharedHeld(const Thread* self) const {
645 DCHECK(self == NULL || self == Thread::Current());
646 bool result;
647 if (UNLIKELY(self == NULL)) { // Handle unattached threads.
648 result = IsExclusiveHeld(self); // TODO: a better best effort here.
649 } else {
650 result = (self->GetHeldMutex(level_) == this);
651 }
652 return result;
653 }
654
Dump(std::ostream & os) const655 void ReaderWriterMutex::Dump(std::ostream& os) const {
656 os << name_
657 << " level=" << static_cast<int>(level_)
658 << " owner=" << GetExclusiveOwnerTid()
659 #if ART_USE_FUTEXES
660 << " state=" << state_.LoadSequentiallyConsistent()
661 << " num_pending_writers=" << num_pending_writers_.LoadSequentiallyConsistent()
662 << " num_pending_readers=" << num_pending_readers_.LoadSequentiallyConsistent()
663 #endif
664 << " ";
665 DumpContention(os);
666 }
667
operator <<(std::ostream & os,const ReaderWriterMutex & mu)668 std::ostream& operator<<(std::ostream& os, const ReaderWriterMutex& mu) {
669 mu.Dump(os);
670 return os;
671 }
672
ConditionVariable(const char * name,Mutex & guard)673 ConditionVariable::ConditionVariable(const char* name, Mutex& guard)
674 : name_(name), guard_(guard) {
675 #if ART_USE_FUTEXES
676 DCHECK_EQ(0, sequence_.LoadRelaxed());
677 num_waiters_ = 0;
678 #else
679 pthread_condattr_t cond_attrs;
680 CHECK_MUTEX_CALL(pthread_condattr_init, (&cond_attrs));
681 #if !defined(__APPLE__)
682 // Apple doesn't have CLOCK_MONOTONIC or pthread_condattr_setclock.
683 CHECK_MUTEX_CALL(pthread_condattr_setclock(&cond_attrs, CLOCK_MONOTONIC));
684 #endif
685 CHECK_MUTEX_CALL(pthread_cond_init, (&cond_, &cond_attrs));
686 #endif
687 }
688
~ConditionVariable()689 ConditionVariable::~ConditionVariable() {
690 #if ART_USE_FUTEXES
691 if (num_waiters_!= 0) {
692 Runtime* runtime = Runtime::Current();
693 bool shutting_down = runtime == nullptr || runtime->IsShuttingDown(Thread::Current());
694 LOG(shutting_down ? WARNING : FATAL) << "ConditionVariable::~ConditionVariable for " << name_
695 << " called with " << num_waiters_ << " waiters.";
696 }
697 #else
698 // We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
699 // may still be using condition variables.
700 int rc = pthread_cond_destroy(&cond_);
701 if (rc != 0) {
702 errno = rc;
703 MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
704 Runtime* runtime = Runtime::Current();
705 bool shutting_down = (runtime == NULL) || runtime->IsShuttingDownLocked();
706 PLOG(shutting_down ? WARNING : FATAL) << "pthread_cond_destroy failed for " << name_;
707 }
708 #endif
709 }
710
Broadcast(Thread * self)711 void ConditionVariable::Broadcast(Thread* self) {
712 DCHECK(self == NULL || self == Thread::Current());
713 // TODO: enable below, there's a race in thread creation that causes false failures currently.
714 // guard_.AssertExclusiveHeld(self);
715 DCHECK_EQ(guard_.GetExclusiveOwnerTid(), SafeGetTid(self));
716 #if ART_USE_FUTEXES
717 if (num_waiters_ > 0) {
718 sequence_++; // Indicate the broadcast occurred.
719 bool done = false;
720 do {
721 int32_t cur_sequence = sequence_.LoadRelaxed();
722 // Requeue waiters onto mutex. The waiter holds the contender count on the mutex high ensuring
723 // mutex unlocks will awaken the requeued waiter thread.
724 done = futex(sequence_.Address(), FUTEX_CMP_REQUEUE, 0,
725 reinterpret_cast<const timespec*>(std::numeric_limits<int32_t>::max()),
726 guard_.state_.Address(), cur_sequence) != -1;
727 if (!done) {
728 if (errno != EAGAIN) {
729 PLOG(FATAL) << "futex cmp requeue failed for " << name_;
730 }
731 }
732 } while (!done);
733 }
734 #else
735 CHECK_MUTEX_CALL(pthread_cond_broadcast, (&cond_));
736 #endif
737 }
738
Signal(Thread * self)739 void ConditionVariable::Signal(Thread* self) {
740 DCHECK(self == NULL || self == Thread::Current());
741 guard_.AssertExclusiveHeld(self);
742 #if ART_USE_FUTEXES
743 if (num_waiters_ > 0) {
744 sequence_++; // Indicate a signal occurred.
745 // Futex wake 1 waiter who will then come and in contend on mutex. It'd be nice to requeue them
746 // to avoid this, however, requeueing can only move all waiters.
747 int num_woken = futex(sequence_.Address(), FUTEX_WAKE, 1, NULL, NULL, 0);
748 // Check something was woken or else we changed sequence_ before they had chance to wait.
749 CHECK((num_woken == 0) || (num_woken == 1));
750 }
751 #else
752 CHECK_MUTEX_CALL(pthread_cond_signal, (&cond_));
753 #endif
754 }
755
Wait(Thread * self)756 void ConditionVariable::Wait(Thread* self) {
757 guard_.CheckSafeToWait(self);
758 WaitHoldingLocks(self);
759 }
760
WaitHoldingLocks(Thread * self)761 void ConditionVariable::WaitHoldingLocks(Thread* self) {
762 DCHECK(self == NULL || self == Thread::Current());
763 guard_.AssertExclusiveHeld(self);
764 unsigned int old_recursion_count = guard_.recursion_count_;
765 #if ART_USE_FUTEXES
766 num_waiters_++;
767 // Ensure the Mutex is contended so that requeued threads are awoken.
768 guard_.num_contenders_++;
769 guard_.recursion_count_ = 1;
770 int32_t cur_sequence = sequence_.LoadRelaxed();
771 guard_.ExclusiveUnlock(self);
772 if (futex(sequence_.Address(), FUTEX_WAIT, cur_sequence, NULL, NULL, 0) != 0) {
773 // Futex failed, check it is an expected error.
774 // EAGAIN == EWOULDBLK, so we let the caller try again.
775 // EINTR implies a signal was sent to this thread.
776 if ((errno != EINTR) && (errno != EAGAIN)) {
777 PLOG(FATAL) << "futex wait failed for " << name_;
778 }
779 }
780 guard_.ExclusiveLock(self);
781 CHECK_GE(num_waiters_, 0);
782 num_waiters_--;
783 // We awoke and so no longer require awakes from the guard_'s unlock.
784 CHECK_GE(guard_.num_contenders_.LoadRelaxed(), 0);
785 guard_.num_contenders_--;
786 #else
787 uint64_t old_owner = guard_.exclusive_owner_;
788 guard_.exclusive_owner_ = 0;
789 guard_.recursion_count_ = 0;
790 CHECK_MUTEX_CALL(pthread_cond_wait, (&cond_, &guard_.mutex_));
791 guard_.exclusive_owner_ = old_owner;
792 #endif
793 guard_.recursion_count_ = old_recursion_count;
794 }
795
TimedWait(Thread * self,int64_t ms,int32_t ns)796 void ConditionVariable::TimedWait(Thread* self, int64_t ms, int32_t ns) {
797 DCHECK(self == NULL || self == Thread::Current());
798 guard_.AssertExclusiveHeld(self);
799 guard_.CheckSafeToWait(self);
800 unsigned int old_recursion_count = guard_.recursion_count_;
801 #if ART_USE_FUTEXES
802 timespec rel_ts;
803 InitTimeSpec(false, CLOCK_REALTIME, ms, ns, &rel_ts);
804 num_waiters_++;
805 // Ensure the Mutex is contended so that requeued threads are awoken.
806 guard_.num_contenders_++;
807 guard_.recursion_count_ = 1;
808 int32_t cur_sequence = sequence_.LoadRelaxed();
809 guard_.ExclusiveUnlock(self);
810 if (futex(sequence_.Address(), FUTEX_WAIT, cur_sequence, &rel_ts, NULL, 0) != 0) {
811 if (errno == ETIMEDOUT) {
812 // Timed out we're done.
813 } else if ((errno == EAGAIN) || (errno == EINTR)) {
814 // A signal or ConditionVariable::Signal/Broadcast has come in.
815 } else {
816 PLOG(FATAL) << "timed futex wait failed for " << name_;
817 }
818 }
819 guard_.ExclusiveLock(self);
820 CHECK_GE(num_waiters_, 0);
821 num_waiters_--;
822 // We awoke and so no longer require awakes from the guard_'s unlock.
823 CHECK_GE(guard_.num_contenders_.LoadRelaxed(), 0);
824 guard_.num_contenders_--;
825 #else
826 #if !defined(__APPLE__)
827 int clock = CLOCK_MONOTONIC;
828 #else
829 int clock = CLOCK_REALTIME;
830 #endif
831 uint64_t old_owner = guard_.exclusive_owner_;
832 guard_.exclusive_owner_ = 0;
833 guard_.recursion_count_ = 0;
834 timespec ts;
835 InitTimeSpec(true, clock, ms, ns, &ts);
836 int rc = TEMP_FAILURE_RETRY(pthread_cond_timedwait(&cond_, &guard_.mutex_, &ts));
837 if (rc != 0 && rc != ETIMEDOUT) {
838 errno = rc;
839 PLOG(FATAL) << "TimedWait failed for " << name_;
840 }
841 guard_.exclusive_owner_ = old_owner;
842 #endif
843 guard_.recursion_count_ = old_recursion_count;
844 }
845
Init()846 void Locks::Init() {
847 if (logging_lock_ != nullptr) {
848 // Already initialized.
849 if (kRuntimeISA == kX86 || kRuntimeISA == kX86_64) {
850 DCHECK(modify_ldt_lock_ != nullptr);
851 } else {
852 DCHECK(modify_ldt_lock_ == nullptr);
853 }
854 DCHECK(abort_lock_ != nullptr);
855 DCHECK(alloc_tracker_lock_ != nullptr);
856 DCHECK(allocated_monitor_ids_lock_ != nullptr);
857 DCHECK(allocated_thread_ids_lock_ != nullptr);
858 DCHECK(breakpoint_lock_ != nullptr);
859 DCHECK(classlinker_classes_lock_ != nullptr);
860 DCHECK(deoptimization_lock_ != nullptr);
861 DCHECK(heap_bitmap_lock_ != nullptr);
862 DCHECK(intern_table_lock_ != nullptr);
863 DCHECK(logging_lock_ != nullptr);
864 DCHECK(mutator_lock_ != nullptr);
865 DCHECK(profiler_lock_ != nullptr);
866 DCHECK(thread_list_lock_ != nullptr);
867 DCHECK(thread_list_suspend_thread_lock_ != nullptr);
868 DCHECK(thread_suspend_count_lock_ != nullptr);
869 DCHECK(trace_lock_ != nullptr);
870 DCHECK(unexpected_signal_lock_ != nullptr);
871 } else {
872 // Create global locks in level order from highest lock level to lowest.
873 LockLevel current_lock_level = kThreadListSuspendThreadLock;
874 DCHECK(thread_list_suspend_thread_lock_ == nullptr);
875 thread_list_suspend_thread_lock_ =
876 new Mutex("thread list suspend thread by .. lock", current_lock_level);
877
878 #define UPDATE_CURRENT_LOCK_LEVEL(new_level) \
879 if (new_level >= current_lock_level) { \
880 /* Do not use CHECKs or FATAL here, abort_lock_ is not setup yet. */ \
881 fprintf(stderr, "New local level %d is not less than current level %d\n", \
882 new_level, current_lock_level); \
883 exit(1); \
884 } \
885 current_lock_level = new_level;
886
887 UPDATE_CURRENT_LOCK_LEVEL(kInstrumentEntrypointsLock);
888 DCHECK(instrument_entrypoints_lock_ == nullptr);
889 instrument_entrypoints_lock_ = new Mutex("instrument entrypoint lock", current_lock_level);
890
891 UPDATE_CURRENT_LOCK_LEVEL(kMutatorLock);
892 DCHECK(mutator_lock_ == nullptr);
893 mutator_lock_ = new ReaderWriterMutex("mutator lock", current_lock_level);
894
895 UPDATE_CURRENT_LOCK_LEVEL(kHeapBitmapLock);
896 DCHECK(heap_bitmap_lock_ == nullptr);
897 heap_bitmap_lock_ = new ReaderWriterMutex("heap bitmap lock", current_lock_level);
898
899 UPDATE_CURRENT_LOCK_LEVEL(kTraceLock);
900 DCHECK(trace_lock_ == nullptr);
901 trace_lock_ = new Mutex("trace lock", current_lock_level);
902
903 UPDATE_CURRENT_LOCK_LEVEL(kRuntimeShutdownLock);
904 DCHECK(runtime_shutdown_lock_ == nullptr);
905 runtime_shutdown_lock_ = new Mutex("runtime shutdown lock", current_lock_level);
906
907 UPDATE_CURRENT_LOCK_LEVEL(kProfilerLock);
908 DCHECK(profiler_lock_ == nullptr);
909 profiler_lock_ = new Mutex("profiler lock", current_lock_level);
910
911 UPDATE_CURRENT_LOCK_LEVEL(kDeoptimizationLock);
912 DCHECK(deoptimization_lock_ == nullptr);
913 deoptimization_lock_ = new Mutex("Deoptimization lock", current_lock_level);
914
915 UPDATE_CURRENT_LOCK_LEVEL(kAllocTrackerLock);
916 DCHECK(alloc_tracker_lock_ == nullptr);
917 alloc_tracker_lock_ = new Mutex("AllocTracker lock", current_lock_level);
918
919 UPDATE_CURRENT_LOCK_LEVEL(kThreadListLock);
920 DCHECK(thread_list_lock_ == nullptr);
921 thread_list_lock_ = new Mutex("thread list lock", current_lock_level);
922
923 UPDATE_CURRENT_LOCK_LEVEL(kBreakpointLock);
924 DCHECK(breakpoint_lock_ == nullptr);
925 breakpoint_lock_ = new ReaderWriterMutex("breakpoint lock", current_lock_level);
926
927 UPDATE_CURRENT_LOCK_LEVEL(kClassLinkerClassesLock);
928 DCHECK(classlinker_classes_lock_ == nullptr);
929 classlinker_classes_lock_ = new ReaderWriterMutex("ClassLinker classes lock",
930 current_lock_level);
931
932 UPDATE_CURRENT_LOCK_LEVEL(kMonitorPoolLock);
933 DCHECK(allocated_monitor_ids_lock_ == nullptr);
934 allocated_monitor_ids_lock_ = new Mutex("allocated monitor ids lock", current_lock_level);
935
936 UPDATE_CURRENT_LOCK_LEVEL(kAllocatedThreadIdsLock);
937 DCHECK(allocated_thread_ids_lock_ == nullptr);
938 allocated_thread_ids_lock_ = new Mutex("allocated thread ids lock", current_lock_level);
939
940 if (kRuntimeISA == kX86 || kRuntimeISA == kX86_64) {
941 UPDATE_CURRENT_LOCK_LEVEL(kModifyLdtLock);
942 DCHECK(modify_ldt_lock_ == nullptr);
943 modify_ldt_lock_ = new Mutex("modify_ldt lock", current_lock_level);
944 }
945
946 UPDATE_CURRENT_LOCK_LEVEL(kInternTableLock);
947 DCHECK(intern_table_lock_ == nullptr);
948 intern_table_lock_ = new Mutex("InternTable lock", current_lock_level);
949
950 UPDATE_CURRENT_LOCK_LEVEL(kReferenceProcessorLock);
951 DCHECK(reference_processor_lock_ == nullptr);
952 reference_processor_lock_ = new Mutex("ReferenceProcessor lock", current_lock_level);
953
954 UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueClearedReferencesLock);
955 DCHECK(reference_queue_cleared_references_lock_ == nullptr);
956 reference_queue_cleared_references_lock_ = new Mutex("ReferenceQueue cleared references lock", current_lock_level);
957
958 UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueWeakReferencesLock);
959 DCHECK(reference_queue_weak_references_lock_ == nullptr);
960 reference_queue_weak_references_lock_ = new Mutex("ReferenceQueue cleared references lock", current_lock_level);
961
962 UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueFinalizerReferencesLock);
963 DCHECK(reference_queue_finalizer_references_lock_ == nullptr);
964 reference_queue_finalizer_references_lock_ = new Mutex("ReferenceQueue finalizer references lock", current_lock_level);
965
966 UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueuePhantomReferencesLock);
967 DCHECK(reference_queue_phantom_references_lock_ == nullptr);
968 reference_queue_phantom_references_lock_ = new Mutex("ReferenceQueue phantom references lock", current_lock_level);
969
970 UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueSoftReferencesLock);
971 DCHECK(reference_queue_soft_references_lock_ == nullptr);
972 reference_queue_soft_references_lock_ = new Mutex("ReferenceQueue soft references lock", current_lock_level);
973
974 UPDATE_CURRENT_LOCK_LEVEL(kAbortLock);
975 DCHECK(abort_lock_ == nullptr);
976 abort_lock_ = new Mutex("abort lock", current_lock_level, true);
977
978 UPDATE_CURRENT_LOCK_LEVEL(kThreadSuspendCountLock);
979 DCHECK(thread_suspend_count_lock_ == nullptr);
980 thread_suspend_count_lock_ = new Mutex("thread suspend count lock", current_lock_level);
981
982 UPDATE_CURRENT_LOCK_LEVEL(kUnexpectedSignalLock);
983 DCHECK(unexpected_signal_lock_ == nullptr);
984 unexpected_signal_lock_ = new Mutex("unexpected signal lock", current_lock_level, true);
985
986 UPDATE_CURRENT_LOCK_LEVEL(kMemMapsLock);
987 DCHECK(mem_maps_lock_ == nullptr);
988 mem_maps_lock_ = new Mutex("mem maps lock", current_lock_level);
989
990 UPDATE_CURRENT_LOCK_LEVEL(kLoggingLock);
991 DCHECK(logging_lock_ == nullptr);
992 logging_lock_ = new Mutex("logging lock", current_lock_level, true);
993
994 #undef UPDATE_CURRENT_LOCK_LEVEL
995 }
996 }
997
998
999 } // namespace art
1000