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 "android-base/stringprintf.h"
23 
24 #include "base/atomic.h"
25 #include "base/logging.h"
26 #include "base/systrace.h"
27 #include "base/time_utils.h"
28 #include "base/value_object.h"
29 #include "mutex-inl.h"
30 #include "scoped_thread_state_change-inl.h"
31 #include "thread-inl.h"
32 
33 namespace art {
34 
35 using android::base::StringPrintf;
36 
37 static Atomic<Locks::ClientCallback*> safe_to_call_abort_callback(nullptr);
38 
39 Mutex* Locks::abort_lock_ = nullptr;
40 Mutex* Locks::alloc_tracker_lock_ = nullptr;
41 Mutex* Locks::allocated_monitor_ids_lock_ = nullptr;
42 Mutex* Locks::allocated_thread_ids_lock_ = nullptr;
43 ReaderWriterMutex* Locks::breakpoint_lock_ = nullptr;
44 ReaderWriterMutex* Locks::classlinker_classes_lock_ = nullptr;
45 Mutex* Locks::deoptimization_lock_ = nullptr;
46 ReaderWriterMutex* Locks::heap_bitmap_lock_ = nullptr;
47 Mutex* Locks::instrument_entrypoints_lock_ = nullptr;
48 Mutex* Locks::intern_table_lock_ = nullptr;
49 Mutex* Locks::jni_function_table_lock_ = nullptr;
50 Mutex* Locks::jni_libraries_lock_ = nullptr;
51 Mutex* Locks::logging_lock_ = nullptr;
52 Mutex* Locks::modify_ldt_lock_ = nullptr;
53 MutatorMutex* Locks::mutator_lock_ = nullptr;
54 Mutex* Locks::profiler_lock_ = nullptr;
55 ReaderWriterMutex* Locks::verifier_deps_lock_ = nullptr;
56 ReaderWriterMutex* Locks::oat_file_manager_lock_ = nullptr;
57 Mutex* Locks::host_dlopen_handles_lock_ = nullptr;
58 Mutex* Locks::reference_processor_lock_ = nullptr;
59 Mutex* Locks::reference_queue_cleared_references_lock_ = nullptr;
60 Mutex* Locks::reference_queue_finalizer_references_lock_ = nullptr;
61 Mutex* Locks::reference_queue_phantom_references_lock_ = nullptr;
62 Mutex* Locks::reference_queue_soft_references_lock_ = nullptr;
63 Mutex* Locks::reference_queue_weak_references_lock_ = nullptr;
64 Mutex* Locks::runtime_shutdown_lock_ = nullptr;
65 Mutex* Locks::cha_lock_ = nullptr;
66 Mutex* Locks::subtype_check_lock_ = nullptr;
67 Mutex* Locks::thread_list_lock_ = nullptr;
68 ConditionVariable* Locks::thread_exit_cond_ = nullptr;
69 Mutex* Locks::thread_suspend_count_lock_ = nullptr;
70 Mutex* Locks::trace_lock_ = nullptr;
71 Mutex* Locks::unexpected_signal_lock_ = nullptr;
72 Mutex* Locks::user_code_suspension_lock_ = nullptr;
73 Uninterruptible Roles::uninterruptible_;
74 ReaderWriterMutex* Locks::jni_globals_lock_ = nullptr;
75 Mutex* Locks::jni_weak_globals_lock_ = nullptr;
76 ReaderWriterMutex* Locks::dex_lock_ = nullptr;
77 Mutex* Locks::native_debug_interface_lock_ = nullptr;
78 std::vector<BaseMutex*> Locks::expected_mutexes_on_weak_ref_access_;
79 Atomic<const BaseMutex*> Locks::expected_mutexes_on_weak_ref_access_guard_;
80 
81 struct AllMutexData {
82   // A guard for all_mutexes_ that's not a mutex (Mutexes must CAS to acquire and busy wait).
83   Atomic<const BaseMutex*> all_mutexes_guard;
84   // All created mutexes guarded by all_mutexes_guard_.
85   std::set<BaseMutex*>* all_mutexes;
AllMutexDataart::AllMutexData86   AllMutexData() : all_mutexes(nullptr) {}
87 };
88 static struct AllMutexData gAllMutexData[kAllMutexDataSize];
89 
90 #if ART_USE_FUTEXES
ComputeRelativeTimeSpec(timespec * result_ts,const timespec & lhs,const timespec & rhs)91 static bool ComputeRelativeTimeSpec(timespec* result_ts, const timespec& lhs, const timespec& rhs) {
92   const int32_t one_sec = 1000 * 1000 * 1000;  // one second in nanoseconds.
93   result_ts->tv_sec = lhs.tv_sec - rhs.tv_sec;
94   result_ts->tv_nsec = lhs.tv_nsec - rhs.tv_nsec;
95   if (result_ts->tv_nsec < 0) {
96     result_ts->tv_sec--;
97     result_ts->tv_nsec += one_sec;
98   } else if (result_ts->tv_nsec > one_sec) {
99     result_ts->tv_sec++;
100     result_ts->tv_nsec -= one_sec;
101   }
102   return result_ts->tv_sec < 0;
103 }
104 #endif
105 
106 // Wait for an amount of time that roughly increases in the argument i.
107 // Spin for small arguments and yield/sleep for longer ones.
BackOff(uint32_t i)108 static void BackOff(uint32_t i) {
109   static constexpr uint32_t kSpinMax = 10;
110   static constexpr uint32_t kYieldMax = 20;
111   if (i <= kSpinMax) {
112     // TODO: Esp. in very latency-sensitive cases, consider replacing this with an explicit
113     // test-and-test-and-set loop in the caller.  Possibly skip entirely on a uniprocessor.
114     volatile uint32_t x = 0;
115     const uint32_t spin_count = 10 * i;
116     for (uint32_t spin = 0; spin < spin_count; ++spin) {
117       ++x;  // Volatile; hence should not be optimized away.
118     }
119     // TODO: Consider adding x86 PAUSE and/or ARM YIELD here.
120   } else if (i <= kYieldMax) {
121     sched_yield();
122   } else {
123     NanoSleep(1000ull * (i - kYieldMax));
124   }
125 }
126 
127 class ScopedAllMutexesLock FINAL {
128  public:
ScopedAllMutexesLock(const BaseMutex * mutex)129   explicit ScopedAllMutexesLock(const BaseMutex* mutex) : mutex_(mutex) {
130     for (uint32_t i = 0;
131          !gAllMutexData->all_mutexes_guard.CompareAndSetWeakAcquire(0, mutex);
132          ++i) {
133       BackOff(i);
134     }
135   }
136 
~ScopedAllMutexesLock()137   ~ScopedAllMutexesLock() {
138     DCHECK_EQ(gAllMutexData->all_mutexes_guard.LoadRelaxed(), mutex_);
139     gAllMutexData->all_mutexes_guard.StoreRelease(0);
140   }
141 
142  private:
143   const BaseMutex* const mutex_;
144 };
145 
146 class Locks::ScopedExpectedMutexesOnWeakRefAccessLock FINAL {
147  public:
ScopedExpectedMutexesOnWeakRefAccessLock(const BaseMutex * mutex)148   explicit ScopedExpectedMutexesOnWeakRefAccessLock(const BaseMutex* mutex) : mutex_(mutex) {
149     for (uint32_t i = 0;
150          !Locks::expected_mutexes_on_weak_ref_access_guard_.CompareAndSetWeakAcquire(0, mutex);
151          ++i) {
152       BackOff(i);
153     }
154   }
155 
~ScopedExpectedMutexesOnWeakRefAccessLock()156   ~ScopedExpectedMutexesOnWeakRefAccessLock() {
157     DCHECK_EQ(Locks::expected_mutexes_on_weak_ref_access_guard_.LoadRelaxed(), mutex_);
158     Locks::expected_mutexes_on_weak_ref_access_guard_.StoreRelease(0);
159   }
160 
161  private:
162   const BaseMutex* const mutex_;
163 };
164 
165 // Scoped class that generates events at the beginning and end of lock contention.
166 class ScopedContentionRecorder FINAL : public ValueObject {
167  public:
ScopedContentionRecorder(BaseMutex * mutex,uint64_t blocked_tid,uint64_t owner_tid)168   ScopedContentionRecorder(BaseMutex* mutex, uint64_t blocked_tid, uint64_t owner_tid)
169       : mutex_(kLogLockContentions ? mutex : nullptr),
170         blocked_tid_(kLogLockContentions ? blocked_tid : 0),
171         owner_tid_(kLogLockContentions ? owner_tid : 0),
172         start_nano_time_(kLogLockContentions ? NanoTime() : 0) {
173     if (ATRACE_ENABLED()) {
174       std::string msg = StringPrintf("Lock contention on %s (owner tid: %" PRIu64 ")",
175                                      mutex->GetName(), owner_tid);
176       ATRACE_BEGIN(msg.c_str());
177     }
178   }
179 
~ScopedContentionRecorder()180   ~ScopedContentionRecorder() {
181     ATRACE_END();
182     if (kLogLockContentions) {
183       uint64_t end_nano_time = NanoTime();
184       mutex_->RecordContention(blocked_tid_, owner_tid_, end_nano_time - start_nano_time_);
185     }
186   }
187 
188  private:
189   BaseMutex* const mutex_;
190   const uint64_t blocked_tid_;
191   const uint64_t owner_tid_;
192   const uint64_t start_nano_time_;
193 };
194 
BaseMutex(const char * name,LockLevel level)195 BaseMutex::BaseMutex(const char* name, LockLevel level)
196     : level_(level),
197       name_(name),
198       should_respond_to_empty_checkpoint_request_(false) {
199   if (kLogLockContentions) {
200     ScopedAllMutexesLock mu(this);
201     std::set<BaseMutex*>** all_mutexes_ptr = &gAllMutexData->all_mutexes;
202     if (*all_mutexes_ptr == nullptr) {
203       // We leak the global set of all mutexes to avoid ordering issues in global variable
204       // construction/destruction.
205       *all_mutexes_ptr = new std::set<BaseMutex*>();
206     }
207     (*all_mutexes_ptr)->insert(this);
208   }
209 }
210 
~BaseMutex()211 BaseMutex::~BaseMutex() {
212   if (kLogLockContentions) {
213     ScopedAllMutexesLock mu(this);
214     gAllMutexData->all_mutexes->erase(this);
215   }
216 }
217 
DumpAll(std::ostream & os)218 void BaseMutex::DumpAll(std::ostream& os) {
219   if (kLogLockContentions) {
220     os << "Mutex logging:\n";
221     ScopedAllMutexesLock mu(reinterpret_cast<const BaseMutex*>(-1));
222     std::set<BaseMutex*>* all_mutexes = gAllMutexData->all_mutexes;
223     if (all_mutexes == nullptr) {
224       // No mutexes have been created yet during at startup.
225       return;
226     }
227     typedef std::set<BaseMutex*>::const_iterator It;
228     os << "(Contended)\n";
229     for (It it = all_mutexes->begin(); it != all_mutexes->end(); ++it) {
230       BaseMutex* mutex = *it;
231       if (mutex->HasEverContended()) {
232         mutex->Dump(os);
233         os << "\n";
234       }
235     }
236     os << "(Never contented)\n";
237     for (It it = all_mutexes->begin(); it != all_mutexes->end(); ++it) {
238       BaseMutex* mutex = *it;
239       if (!mutex->HasEverContended()) {
240         mutex->Dump(os);
241         os << "\n";
242       }
243     }
244   }
245 }
246 
CheckSafeToWait(Thread * self)247 void BaseMutex::CheckSafeToWait(Thread* self) {
248   if (self == nullptr) {
249     CheckUnattachedThread(level_);
250     return;
251   }
252   if (kDebugLocking) {
253     CHECK(self->GetHeldMutex(level_) == this || level_ == kMonitorLock)
254         << "Waiting on unacquired mutex: " << name_;
255     bool bad_mutexes_held = false;
256     for (int i = kLockLevelCount - 1; i >= 0; --i) {
257       if (i != level_) {
258         BaseMutex* held_mutex = self->GetHeldMutex(static_cast<LockLevel>(i));
259         // We allow the thread to wait even if the user_code_suspension_lock_ is held so long as we
260         // are some thread's resume_cond_ (level_ == kThreadSuspendCountLock). This just means that
261         // gc or some other internal process is suspending the thread while it is trying to suspend
262         // some other thread. So long as the current thread is not being suspended by a
263         // SuspendReason::kForUserCode (which needs the user_code_suspension_lock_ to clear) this is
264         // fine.
265         if (held_mutex == Locks::user_code_suspension_lock_ && level_ == kThreadSuspendCountLock) {
266           // No thread safety analysis is fine since we have both the user_code_suspension_lock_
267           // from the line above and the ThreadSuspendCountLock since it is our level_. We use this
268           // lambda to avoid having to annotate the whole function as NO_THREAD_SAFETY_ANALYSIS.
269           auto is_suspending_for_user_code = [self]() NO_THREAD_SAFETY_ANALYSIS {
270             return self->GetUserCodeSuspendCount() != 0;
271           };
272           if (is_suspending_for_user_code()) {
273             LOG(ERROR) << "Holding \"" << held_mutex->name_ << "\" "
274                       << "(level " << LockLevel(i) << ") while performing wait on "
275                       << "\"" << name_ << "\" (level " << level_ << ") "
276                       << "with SuspendReason::kForUserCode pending suspensions";
277             bad_mutexes_held = true;
278           }
279         } else if (held_mutex != nullptr) {
280           LOG(ERROR) << "Holding \"" << held_mutex->name_ << "\" "
281                      << "(level " << LockLevel(i) << ") while performing wait on "
282                      << "\"" << name_ << "\" (level " << level_ << ")";
283           bad_mutexes_held = true;
284         }
285       }
286     }
287     if (gAborting == 0) {  // Avoid recursive aborts.
288       CHECK(!bad_mutexes_held) << this;
289     }
290   }
291 }
292 
AddToWaitTime(uint64_t value)293 void BaseMutex::ContentionLogData::AddToWaitTime(uint64_t value) {
294   if (kLogLockContentions) {
295     // Atomically add value to wait_time.
296     wait_time.FetchAndAddSequentiallyConsistent(value);
297   }
298 }
299 
RecordContention(uint64_t blocked_tid,uint64_t owner_tid,uint64_t nano_time_blocked)300 void BaseMutex::RecordContention(uint64_t blocked_tid,
301                                  uint64_t owner_tid,
302                                  uint64_t nano_time_blocked) {
303   if (kLogLockContentions) {
304     ContentionLogData* data = contention_log_data_;
305     ++(data->contention_count);
306     data->AddToWaitTime(nano_time_blocked);
307     ContentionLogEntry* log = data->contention_log;
308     // This code is intentionally racy as it is only used for diagnostics.
309     uint32_t slot = data->cur_content_log_entry.LoadRelaxed();
310     if (log[slot].blocked_tid == blocked_tid &&
311         log[slot].owner_tid == blocked_tid) {
312       ++log[slot].count;
313     } else {
314       uint32_t new_slot;
315       do {
316         slot = data->cur_content_log_entry.LoadRelaxed();
317         new_slot = (slot + 1) % kContentionLogSize;
318       } while (!data->cur_content_log_entry.CompareAndSetWeakRelaxed(slot, new_slot));
319       log[new_slot].blocked_tid = blocked_tid;
320       log[new_slot].owner_tid = owner_tid;
321       log[new_slot].count.StoreRelaxed(1);
322     }
323   }
324 }
325 
DumpContention(std::ostream & os) const326 void BaseMutex::DumpContention(std::ostream& os) const {
327   if (kLogLockContentions) {
328     const ContentionLogData* data = contention_log_data_;
329     const ContentionLogEntry* log = data->contention_log;
330     uint64_t wait_time = data->wait_time.LoadRelaxed();
331     uint32_t contention_count = data->contention_count.LoadRelaxed();
332     if (contention_count == 0) {
333       os << "never contended";
334     } else {
335       os << "contended " << contention_count
336          << " total wait of contender " << PrettyDuration(wait_time)
337          << " average " << PrettyDuration(wait_time / contention_count);
338       SafeMap<uint64_t, size_t> most_common_blocker;
339       SafeMap<uint64_t, size_t> most_common_blocked;
340       for (size_t i = 0; i < kContentionLogSize; ++i) {
341         uint64_t blocked_tid = log[i].blocked_tid;
342         uint64_t owner_tid = log[i].owner_tid;
343         uint32_t count = log[i].count.LoadRelaxed();
344         if (count > 0) {
345           auto it = most_common_blocked.find(blocked_tid);
346           if (it != most_common_blocked.end()) {
347             most_common_blocked.Overwrite(blocked_tid, it->second + count);
348           } else {
349             most_common_blocked.Put(blocked_tid, count);
350           }
351           it = most_common_blocker.find(owner_tid);
352           if (it != most_common_blocker.end()) {
353             most_common_blocker.Overwrite(owner_tid, it->second + count);
354           } else {
355             most_common_blocker.Put(owner_tid, count);
356           }
357         }
358       }
359       uint64_t max_tid = 0;
360       size_t max_tid_count = 0;
361       for (const auto& pair : most_common_blocked) {
362         if (pair.second > max_tid_count) {
363           max_tid = pair.first;
364           max_tid_count = pair.second;
365         }
366       }
367       if (max_tid != 0) {
368         os << " sample shows most blocked tid=" << max_tid;
369       }
370       max_tid = 0;
371       max_tid_count = 0;
372       for (const auto& pair : most_common_blocker) {
373         if (pair.second > max_tid_count) {
374           max_tid = pair.first;
375           max_tid_count = pair.second;
376         }
377       }
378       if (max_tid != 0) {
379         os << " sample shows tid=" << max_tid << " owning during this time";
380       }
381     }
382   }
383 }
384 
385 
Mutex(const char * name,LockLevel level,bool recursive)386 Mutex::Mutex(const char* name, LockLevel level, bool recursive)
387     : BaseMutex(name, level), exclusive_owner_(0), recursive_(recursive), recursion_count_(0) {
388 #if ART_USE_FUTEXES
389   DCHECK_EQ(0, state_.LoadRelaxed());
390   DCHECK_EQ(0, num_contenders_.LoadRelaxed());
391 #else
392   CHECK_MUTEX_CALL(pthread_mutex_init, (&mutex_, nullptr));
393 #endif
394 }
395 
396 // Helper to allow checking shutdown while locking for thread safety.
IsSafeToCallAbortSafe()397 static bool IsSafeToCallAbortSafe() {
398   MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
399   return Locks::IsSafeToCallAbortRacy();
400 }
401 
~Mutex()402 Mutex::~Mutex() {
403   bool safe_to_call_abort = Locks::IsSafeToCallAbortRacy();
404 #if ART_USE_FUTEXES
405   if (state_.LoadRelaxed() != 0) {
406     LOG(safe_to_call_abort ? FATAL : WARNING)
407         << "destroying mutex with owner: " << GetExclusiveOwnerTid();
408   } else {
409     if (GetExclusiveOwnerTid() != 0) {
410       LOG(safe_to_call_abort ? FATAL : WARNING)
411           << "unexpectedly found an owner on unlocked mutex " << name_;
412     }
413     if (num_contenders_.LoadSequentiallyConsistent() != 0) {
414       LOG(safe_to_call_abort ? FATAL : WARNING)
415           << "unexpectedly found a contender on mutex " << name_;
416     }
417   }
418 #else
419   // We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
420   // may still be using locks.
421   int rc = pthread_mutex_destroy(&mutex_);
422   if (rc != 0) {
423     errno = rc;
424     PLOG(safe_to_call_abort ? FATAL : WARNING)
425         << "pthread_mutex_destroy failed for " << name_;
426   }
427 #endif
428 }
429 
ExclusiveLock(Thread * self)430 void Mutex::ExclusiveLock(Thread* self) {
431   DCHECK(self == nullptr || self == Thread::Current());
432   if (kDebugLocking && !recursive_) {
433     AssertNotHeld(self);
434   }
435   if (!recursive_ || !IsExclusiveHeld(self)) {
436 #if ART_USE_FUTEXES
437     bool done = false;
438     do {
439       int32_t cur_state = state_.LoadRelaxed();
440       if (LIKELY(cur_state == 0)) {
441         // Change state from 0 to 1 and impose load/store ordering appropriate for lock acquisition.
442         done = state_.CompareAndSetWeakAcquire(0 /* cur_state */, 1 /* new state */);
443       } else {
444         // Failed to acquire, hang up.
445         ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
446         num_contenders_++;
447         if (UNLIKELY(should_respond_to_empty_checkpoint_request_)) {
448           self->CheckEmptyCheckpointFromMutex();
449         }
450         if (futex(state_.Address(), FUTEX_WAIT, 1, nullptr, nullptr, 0) != 0) {
451           // EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
452           // We don't use TEMP_FAILURE_RETRY so we can intentionally retry to acquire the lock.
453           if ((errno != EAGAIN) && (errno != EINTR)) {
454             PLOG(FATAL) << "futex wait failed for " << name_;
455           }
456         }
457         num_contenders_--;
458       }
459     } while (!done);
460     DCHECK_EQ(state_.LoadRelaxed(), 1);
461 #else
462     CHECK_MUTEX_CALL(pthread_mutex_lock, (&mutex_));
463 #endif
464     DCHECK_EQ(GetExclusiveOwnerTid(), 0);
465     exclusive_owner_.StoreRelaxed(SafeGetTid(self));
466     RegisterAsLocked(self);
467   }
468   recursion_count_++;
469   if (kDebugLocking) {
470     CHECK(recursion_count_ == 1 || recursive_) << "Unexpected recursion count on mutex: "
471         << name_ << " " << recursion_count_;
472     AssertHeld(self);
473   }
474 }
475 
ExclusiveTryLock(Thread * self)476 bool Mutex::ExclusiveTryLock(Thread* self) {
477   DCHECK(self == nullptr || self == Thread::Current());
478   if (kDebugLocking && !recursive_) {
479     AssertNotHeld(self);
480   }
481   if (!recursive_ || !IsExclusiveHeld(self)) {
482 #if ART_USE_FUTEXES
483     bool done = false;
484     do {
485       int32_t cur_state = state_.LoadRelaxed();
486       if (cur_state == 0) {
487         // Change state from 0 to 1 and impose load/store ordering appropriate for lock acquisition.
488         done = state_.CompareAndSetWeakAcquire(0 /* cur_state */, 1 /* new state */);
489       } else {
490         return false;
491       }
492     } while (!done);
493     DCHECK_EQ(state_.LoadRelaxed(), 1);
494 #else
495     int result = pthread_mutex_trylock(&mutex_);
496     if (result == EBUSY) {
497       return false;
498     }
499     if (result != 0) {
500       errno = result;
501       PLOG(FATAL) << "pthread_mutex_trylock failed for " << name_;
502     }
503 #endif
504     DCHECK_EQ(GetExclusiveOwnerTid(), 0);
505     exclusive_owner_.StoreRelaxed(SafeGetTid(self));
506     RegisterAsLocked(self);
507   }
508   recursion_count_++;
509   if (kDebugLocking) {
510     CHECK(recursion_count_ == 1 || recursive_) << "Unexpected recursion count on mutex: "
511         << name_ << " " << recursion_count_;
512     AssertHeld(self);
513   }
514   return true;
515 }
516 
ExclusiveUnlock(Thread * self)517 void Mutex::ExclusiveUnlock(Thread* self) {
518   if (kIsDebugBuild && self != nullptr && self != Thread::Current()) {
519     std::string name1 = "<null>";
520     std::string name2 = "<null>";
521     if (self != nullptr) {
522       self->GetThreadName(name1);
523     }
524     if (Thread::Current() != nullptr) {
525       Thread::Current()->GetThreadName(name2);
526     }
527     LOG(FATAL) << GetName() << " level=" << level_ << " self=" << name1
528                << " Thread::Current()=" << name2;
529   }
530   AssertHeld(self);
531   DCHECK_NE(GetExclusiveOwnerTid(), 0);
532   recursion_count_--;
533   if (!recursive_ || recursion_count_ == 0) {
534     if (kDebugLocking) {
535       CHECK(recursion_count_ == 0 || recursive_) << "Unexpected recursion count on mutex: "
536           << name_ << " " << recursion_count_;
537     }
538     RegisterAsUnlocked(self);
539 #if ART_USE_FUTEXES
540     bool done = false;
541     do {
542       int32_t cur_state = state_.LoadRelaxed();
543       if (LIKELY(cur_state == 1)) {
544         // We're no longer the owner.
545         exclusive_owner_.StoreRelaxed(0);
546         // Change state to 0 and impose load/store ordering appropriate for lock release.
547         // Note, the relaxed loads below mustn't reorder before the CompareAndSet.
548         // TODO: the ordering here is non-trivial as state is split across 3 fields, fix by placing
549         // a status bit into the state on contention.
550         done = state_.CompareAndSetWeakSequentiallyConsistent(cur_state, 0 /* new state */);
551         if (LIKELY(done)) {  // Spurious fail?
552           // Wake a contender.
553           if (UNLIKELY(num_contenders_.LoadRelaxed() > 0)) {
554             futex(state_.Address(), FUTEX_WAKE, 1, nullptr, nullptr, 0);
555           }
556         }
557       } else {
558         // Logging acquires the logging lock, avoid infinite recursion in that case.
559         if (this != Locks::logging_lock_) {
560           LOG(FATAL) << "Unexpected state_ in unlock " << cur_state << " for " << name_;
561         } else {
562           LogHelper::LogLineLowStack(__FILE__,
563                                      __LINE__,
564                                      ::android::base::FATAL_WITHOUT_ABORT,
565                                      StringPrintf("Unexpected state_ %d in unlock for %s",
566                                                   cur_state, name_).c_str());
567           _exit(1);
568         }
569       }
570     } while (!done);
571 #else
572     exclusive_owner_.StoreRelaxed(0);
573     CHECK_MUTEX_CALL(pthread_mutex_unlock, (&mutex_));
574 #endif
575   }
576 }
577 
Dump(std::ostream & os) const578 void Mutex::Dump(std::ostream& os) const {
579   os << (recursive_ ? "recursive " : "non-recursive ")
580       << name_
581       << " level=" << static_cast<int>(level_)
582       << " rec=" << recursion_count_
583       << " owner=" << GetExclusiveOwnerTid() << " ";
584   DumpContention(os);
585 }
586 
operator <<(std::ostream & os,const Mutex & mu)587 std::ostream& operator<<(std::ostream& os, const Mutex& mu) {
588   mu.Dump(os);
589   return os;
590 }
591 
WakeupToRespondToEmptyCheckpoint()592 void Mutex::WakeupToRespondToEmptyCheckpoint() {
593 #if ART_USE_FUTEXES
594   // Wake up all the waiters so they will respond to the emtpy checkpoint.
595   DCHECK(should_respond_to_empty_checkpoint_request_);
596   if (UNLIKELY(num_contenders_.LoadRelaxed() > 0)) {
597     futex(state_.Address(), FUTEX_WAKE, -1, nullptr, nullptr, 0);
598   }
599 #else
600   LOG(FATAL) << "Non futex case isn't supported.";
601 #endif
602 }
603 
ReaderWriterMutex(const char * name,LockLevel level)604 ReaderWriterMutex::ReaderWriterMutex(const char* name, LockLevel level)
605     : BaseMutex(name, level)
606 #if ART_USE_FUTEXES
607     , state_(0), num_pending_readers_(0), num_pending_writers_(0)
608 #endif
609 {
610 #if !ART_USE_FUTEXES
611   CHECK_MUTEX_CALL(pthread_rwlock_init, (&rwlock_, nullptr));
612 #endif
613   exclusive_owner_.StoreRelaxed(0);
614 }
615 
~ReaderWriterMutex()616 ReaderWriterMutex::~ReaderWriterMutex() {
617 #if ART_USE_FUTEXES
618   CHECK_EQ(state_.LoadRelaxed(), 0);
619   CHECK_EQ(GetExclusiveOwnerTid(), 0);
620   CHECK_EQ(num_pending_readers_.LoadRelaxed(), 0);
621   CHECK_EQ(num_pending_writers_.LoadRelaxed(), 0);
622 #else
623   // We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
624   // may still be using locks.
625   int rc = pthread_rwlock_destroy(&rwlock_);
626   if (rc != 0) {
627     errno = rc;
628     bool is_safe_to_call_abort = IsSafeToCallAbortSafe();
629     PLOG(is_safe_to_call_abort ? FATAL : WARNING) << "pthread_rwlock_destroy failed for " << name_;
630   }
631 #endif
632 }
633 
ExclusiveLock(Thread * self)634 void ReaderWriterMutex::ExclusiveLock(Thread* self) {
635   DCHECK(self == nullptr || self == Thread::Current());
636   AssertNotExclusiveHeld(self);
637 #if ART_USE_FUTEXES
638   bool done = false;
639   do {
640     int32_t cur_state = state_.LoadRelaxed();
641     if (LIKELY(cur_state == 0)) {
642       // Change state from 0 to -1 and impose load/store ordering appropriate for lock acquisition.
643       done = state_.CompareAndSetWeakAcquire(0 /* cur_state*/, -1 /* new state */);
644     } else {
645       // Failed to acquire, hang up.
646       ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
647       ++num_pending_writers_;
648       if (UNLIKELY(should_respond_to_empty_checkpoint_request_)) {
649         self->CheckEmptyCheckpointFromMutex();
650       }
651       if (futex(state_.Address(), FUTEX_WAIT, cur_state, nullptr, nullptr, 0) != 0) {
652         // EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
653         // We don't use TEMP_FAILURE_RETRY so we can intentionally retry to acquire the lock.
654         if ((errno != EAGAIN) && (errno != EINTR)) {
655           PLOG(FATAL) << "futex wait failed for " << name_;
656         }
657       }
658       --num_pending_writers_;
659     }
660   } while (!done);
661   DCHECK_EQ(state_.LoadRelaxed(), -1);
662 #else
663   CHECK_MUTEX_CALL(pthread_rwlock_wrlock, (&rwlock_));
664 #endif
665   DCHECK_EQ(GetExclusiveOwnerTid(), 0);
666   exclusive_owner_.StoreRelaxed(SafeGetTid(self));
667   RegisterAsLocked(self);
668   AssertExclusiveHeld(self);
669 }
670 
ExclusiveUnlock(Thread * self)671 void ReaderWriterMutex::ExclusiveUnlock(Thread* self) {
672   DCHECK(self == nullptr || self == Thread::Current());
673   AssertExclusiveHeld(self);
674   RegisterAsUnlocked(self);
675   DCHECK_NE(GetExclusiveOwnerTid(), 0);
676 #if ART_USE_FUTEXES
677   bool done = false;
678   do {
679     int32_t cur_state = state_.LoadRelaxed();
680     if (LIKELY(cur_state == -1)) {
681       // We're no longer the owner.
682       exclusive_owner_.StoreRelaxed(0);
683       // Change state from -1 to 0 and impose load/store ordering appropriate for lock release.
684       // Note, the relaxed loads below musn't reorder before the CompareAndSet.
685       // TODO: the ordering here is non-trivial as state is split across 3 fields, fix by placing
686       // a status bit into the state on contention.
687       done = state_.CompareAndSetWeakSequentiallyConsistent(-1 /* cur_state*/, 0 /* new state */);
688       if (LIKELY(done)) {  // Weak CAS may fail spuriously.
689         // Wake any waiters.
690         if (UNLIKELY(num_pending_readers_.LoadRelaxed() > 0 ||
691                      num_pending_writers_.LoadRelaxed() > 0)) {
692           futex(state_.Address(), FUTEX_WAKE, -1, nullptr, nullptr, 0);
693         }
694       }
695     } else {
696       LOG(FATAL) << "Unexpected state_:" << cur_state << " for " << name_;
697     }
698   } while (!done);
699 #else
700   exclusive_owner_.StoreRelaxed(0);
701   CHECK_MUTEX_CALL(pthread_rwlock_unlock, (&rwlock_));
702 #endif
703 }
704 
705 #if HAVE_TIMED_RWLOCK
ExclusiveLockWithTimeout(Thread * self,int64_t ms,int32_t ns)706 bool ReaderWriterMutex::ExclusiveLockWithTimeout(Thread* self, int64_t ms, int32_t ns) {
707   DCHECK(self == nullptr || self == Thread::Current());
708 #if ART_USE_FUTEXES
709   bool done = false;
710   timespec end_abs_ts;
711   InitTimeSpec(true, CLOCK_MONOTONIC, ms, ns, &end_abs_ts);
712   do {
713     int32_t cur_state = state_.LoadRelaxed();
714     if (cur_state == 0) {
715       // Change state from 0 to -1 and impose load/store ordering appropriate for lock acquisition.
716       done = state_.CompareAndSetWeakAcquire(0 /* cur_state */, -1 /* new state */);
717     } else {
718       // Failed to acquire, hang up.
719       timespec now_abs_ts;
720       InitTimeSpec(true, CLOCK_MONOTONIC, 0, 0, &now_abs_ts);
721       timespec rel_ts;
722       if (ComputeRelativeTimeSpec(&rel_ts, end_abs_ts, now_abs_ts)) {
723         return false;  // Timed out.
724       }
725       ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
726       ++num_pending_writers_;
727       if (UNLIKELY(should_respond_to_empty_checkpoint_request_)) {
728         self->CheckEmptyCheckpointFromMutex();
729       }
730       if (futex(state_.Address(), FUTEX_WAIT, cur_state, &rel_ts, nullptr, 0) != 0) {
731         if (errno == ETIMEDOUT) {
732           --num_pending_writers_;
733           return false;  // Timed out.
734         } else if ((errno != EAGAIN) && (errno != EINTR)) {
735           // EAGAIN and EINTR both indicate a spurious failure,
736           // recompute the relative time out from now and try again.
737           // We don't use TEMP_FAILURE_RETRY so we can recompute rel_ts;
738           PLOG(FATAL) << "timed futex wait failed for " << name_;
739         }
740       }
741       --num_pending_writers_;
742     }
743   } while (!done);
744 #else
745   timespec ts;
746   InitTimeSpec(true, CLOCK_REALTIME, ms, ns, &ts);
747   int result = pthread_rwlock_timedwrlock(&rwlock_, &ts);
748   if (result == ETIMEDOUT) {
749     return false;
750   }
751   if (result != 0) {
752     errno = result;
753     PLOG(FATAL) << "pthread_rwlock_timedwrlock failed for " << name_;
754   }
755 #endif
756   exclusive_owner_.StoreRelaxed(SafeGetTid(self));
757   RegisterAsLocked(self);
758   AssertSharedHeld(self);
759   return true;
760 }
761 #endif
762 
763 #if ART_USE_FUTEXES
HandleSharedLockContention(Thread * self,int32_t cur_state)764 void ReaderWriterMutex::HandleSharedLockContention(Thread* self, int32_t cur_state) {
765   // Owner holds it exclusively, hang up.
766   ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
767   ++num_pending_readers_;
768   if (UNLIKELY(should_respond_to_empty_checkpoint_request_)) {
769     self->CheckEmptyCheckpointFromMutex();
770   }
771   if (futex(state_.Address(), FUTEX_WAIT, cur_state, nullptr, nullptr, 0) != 0) {
772     if (errno != EAGAIN && errno != EINTR) {
773       PLOG(FATAL) << "futex wait failed for " << name_;
774     }
775   }
776   --num_pending_readers_;
777 }
778 #endif
779 
SharedTryLock(Thread * self)780 bool ReaderWriterMutex::SharedTryLock(Thread* self) {
781   DCHECK(self == nullptr || self == Thread::Current());
782 #if ART_USE_FUTEXES
783   bool done = false;
784   do {
785     int32_t cur_state = state_.LoadRelaxed();
786     if (cur_state >= 0) {
787       // Add as an extra reader and impose load/store ordering appropriate for lock acquisition.
788       done = state_.CompareAndSetWeakAcquire(cur_state, cur_state + 1);
789     } else {
790       // Owner holds it exclusively.
791       return false;
792     }
793   } while (!done);
794 #else
795   int result = pthread_rwlock_tryrdlock(&rwlock_);
796   if (result == EBUSY) {
797     return false;
798   }
799   if (result != 0) {
800     errno = result;
801     PLOG(FATAL) << "pthread_mutex_trylock failed for " << name_;
802   }
803 #endif
804   RegisterAsLocked(self);
805   AssertSharedHeld(self);
806   return true;
807 }
808 
IsSharedHeld(const Thread * self) const809 bool ReaderWriterMutex::IsSharedHeld(const Thread* self) const {
810   DCHECK(self == nullptr || self == Thread::Current());
811   bool result;
812   if (UNLIKELY(self == nullptr)) {  // Handle unattached threads.
813     result = IsExclusiveHeld(self);  // TODO: a better best effort here.
814   } else {
815     result = (self->GetHeldMutex(level_) == this);
816   }
817   return result;
818 }
819 
Dump(std::ostream & os) const820 void ReaderWriterMutex::Dump(std::ostream& os) const {
821   os << name_
822       << " level=" << static_cast<int>(level_)
823       << " owner=" << GetExclusiveOwnerTid()
824 #if ART_USE_FUTEXES
825       << " state=" << state_.LoadSequentiallyConsistent()
826       << " num_pending_writers=" << num_pending_writers_.LoadSequentiallyConsistent()
827       << " num_pending_readers=" << num_pending_readers_.LoadSequentiallyConsistent()
828 #endif
829       << " ";
830   DumpContention(os);
831 }
832 
operator <<(std::ostream & os,const ReaderWriterMutex & mu)833 std::ostream& operator<<(std::ostream& os, const ReaderWriterMutex& mu) {
834   mu.Dump(os);
835   return os;
836 }
837 
operator <<(std::ostream & os,const MutatorMutex & mu)838 std::ostream& operator<<(std::ostream& os, const MutatorMutex& mu) {
839   mu.Dump(os);
840   return os;
841 }
842 
WakeupToRespondToEmptyCheckpoint()843 void ReaderWriterMutex::WakeupToRespondToEmptyCheckpoint() {
844 #if ART_USE_FUTEXES
845   // Wake up all the waiters so they will respond to the emtpy checkpoint.
846   DCHECK(should_respond_to_empty_checkpoint_request_);
847   if (UNLIKELY(num_pending_readers_.LoadRelaxed() > 0 ||
848                num_pending_writers_.LoadRelaxed() > 0)) {
849     futex(state_.Address(), FUTEX_WAKE, -1, nullptr, nullptr, 0);
850   }
851 #else
852   LOG(FATAL) << "Non futex case isn't supported.";
853 #endif
854 }
855 
ConditionVariable(const char * name,Mutex & guard)856 ConditionVariable::ConditionVariable(const char* name, Mutex& guard)
857     : name_(name), guard_(guard) {
858 #if ART_USE_FUTEXES
859   DCHECK_EQ(0, sequence_.LoadRelaxed());
860   num_waiters_ = 0;
861 #else
862   pthread_condattr_t cond_attrs;
863   CHECK_MUTEX_CALL(pthread_condattr_init, (&cond_attrs));
864 #if !defined(__APPLE__)
865   // Apple doesn't have CLOCK_MONOTONIC or pthread_condattr_setclock.
866   CHECK_MUTEX_CALL(pthread_condattr_setclock, (&cond_attrs, CLOCK_MONOTONIC));
867 #endif
868   CHECK_MUTEX_CALL(pthread_cond_init, (&cond_, &cond_attrs));
869 #endif
870 }
871 
~ConditionVariable()872 ConditionVariable::~ConditionVariable() {
873 #if ART_USE_FUTEXES
874   if (num_waiters_!= 0) {
875     bool is_safe_to_call_abort = IsSafeToCallAbortSafe();
876     LOG(is_safe_to_call_abort ? FATAL : WARNING)
877         << "ConditionVariable::~ConditionVariable for " << name_
878         << " called with " << num_waiters_ << " waiters.";
879   }
880 #else
881   // We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
882   // may still be using condition variables.
883   int rc = pthread_cond_destroy(&cond_);
884   if (rc != 0) {
885     errno = rc;
886     bool is_safe_to_call_abort = IsSafeToCallAbortSafe();
887     PLOG(is_safe_to_call_abort ? FATAL : WARNING) << "pthread_cond_destroy failed for " << name_;
888   }
889 #endif
890 }
891 
Broadcast(Thread * self)892 void ConditionVariable::Broadcast(Thread* self) {
893   DCHECK(self == nullptr || self == Thread::Current());
894   // TODO: enable below, there's a race in thread creation that causes false failures currently.
895   // guard_.AssertExclusiveHeld(self);
896   DCHECK_EQ(guard_.GetExclusiveOwnerTid(), SafeGetTid(self));
897 #if ART_USE_FUTEXES
898   if (num_waiters_ > 0) {
899     sequence_++;  // Indicate the broadcast occurred.
900     bool done = false;
901     do {
902       int32_t cur_sequence = sequence_.LoadRelaxed();
903       // Requeue waiters onto mutex. The waiter holds the contender count on the mutex high ensuring
904       // mutex unlocks will awaken the requeued waiter thread.
905       done = futex(sequence_.Address(), FUTEX_CMP_REQUEUE, 0,
906                    reinterpret_cast<const timespec*>(std::numeric_limits<int32_t>::max()),
907                    guard_.state_.Address(), cur_sequence) != -1;
908       if (!done) {
909         if (errno != EAGAIN && errno != EINTR) {
910           PLOG(FATAL) << "futex cmp requeue failed for " << name_;
911         }
912       }
913     } while (!done);
914   }
915 #else
916   CHECK_MUTEX_CALL(pthread_cond_broadcast, (&cond_));
917 #endif
918 }
919 
Signal(Thread * self)920 void ConditionVariable::Signal(Thread* self) {
921   DCHECK(self == nullptr || self == Thread::Current());
922   guard_.AssertExclusiveHeld(self);
923 #if ART_USE_FUTEXES
924   if (num_waiters_ > 0) {
925     sequence_++;  // Indicate a signal occurred.
926     // Futex wake 1 waiter who will then come and in contend on mutex. It'd be nice to requeue them
927     // to avoid this, however, requeueing can only move all waiters.
928     int num_woken = futex(sequence_.Address(), FUTEX_WAKE, 1, nullptr, nullptr, 0);
929     // Check something was woken or else we changed sequence_ before they had chance to wait.
930     CHECK((num_woken == 0) || (num_woken == 1));
931   }
932 #else
933   CHECK_MUTEX_CALL(pthread_cond_signal, (&cond_));
934 #endif
935 }
936 
Wait(Thread * self)937 void ConditionVariable::Wait(Thread* self) {
938   guard_.CheckSafeToWait(self);
939   WaitHoldingLocks(self);
940 }
941 
WaitHoldingLocks(Thread * self)942 void ConditionVariable::WaitHoldingLocks(Thread* self) {
943   DCHECK(self == nullptr || self == Thread::Current());
944   guard_.AssertExclusiveHeld(self);
945   unsigned int old_recursion_count = guard_.recursion_count_;
946 #if ART_USE_FUTEXES
947   num_waiters_++;
948   // Ensure the Mutex is contended so that requeued threads are awoken.
949   guard_.num_contenders_++;
950   guard_.recursion_count_ = 1;
951   int32_t cur_sequence = sequence_.LoadRelaxed();
952   guard_.ExclusiveUnlock(self);
953   if (futex(sequence_.Address(), FUTEX_WAIT, cur_sequence, nullptr, nullptr, 0) != 0) {
954     // Futex failed, check it is an expected error.
955     // EAGAIN == EWOULDBLK, so we let the caller try again.
956     // EINTR implies a signal was sent to this thread.
957     if ((errno != EINTR) && (errno != EAGAIN)) {
958       PLOG(FATAL) << "futex wait failed for " << name_;
959     }
960   }
961   if (self != nullptr) {
962     JNIEnvExt* const env = self->GetJniEnv();
963     if (UNLIKELY(env != nullptr && env->IsRuntimeDeleted())) {
964       CHECK(self->IsDaemon());
965       // If the runtime has been deleted, then we cannot proceed. Just sleep forever. This may
966       // occur for user daemon threads that get a spurious wakeup. This occurs for test 132 with
967       // --host and --gdb.
968       // After we wake up, the runtime may have been shutdown, which means that this condition may
969       // have been deleted. It is not safe to retry the wait.
970       SleepForever();
971     }
972   }
973   guard_.ExclusiveLock(self);
974   CHECK_GE(num_waiters_, 0);
975   num_waiters_--;
976   // We awoke and so no longer require awakes from the guard_'s unlock.
977   CHECK_GE(guard_.num_contenders_.LoadRelaxed(), 0);
978   guard_.num_contenders_--;
979 #else
980   pid_t old_owner = guard_.GetExclusiveOwnerTid();
981   guard_.exclusive_owner_.StoreRelaxed(0);
982   guard_.recursion_count_ = 0;
983   CHECK_MUTEX_CALL(pthread_cond_wait, (&cond_, &guard_.mutex_));
984   guard_.exclusive_owner_.StoreRelaxed(old_owner);
985 #endif
986   guard_.recursion_count_ = old_recursion_count;
987 }
988 
TimedWait(Thread * self,int64_t ms,int32_t ns)989 bool ConditionVariable::TimedWait(Thread* self, int64_t ms, int32_t ns) {
990   DCHECK(self == nullptr || self == Thread::Current());
991   bool timed_out = false;
992   guard_.AssertExclusiveHeld(self);
993   guard_.CheckSafeToWait(self);
994   unsigned int old_recursion_count = guard_.recursion_count_;
995 #if ART_USE_FUTEXES
996   timespec rel_ts;
997   InitTimeSpec(false, CLOCK_REALTIME, ms, ns, &rel_ts);
998   num_waiters_++;
999   // Ensure the Mutex is contended so that requeued threads are awoken.
1000   guard_.num_contenders_++;
1001   guard_.recursion_count_ = 1;
1002   int32_t cur_sequence = sequence_.LoadRelaxed();
1003   guard_.ExclusiveUnlock(self);
1004   if (futex(sequence_.Address(), FUTEX_WAIT, cur_sequence, &rel_ts, nullptr, 0) != 0) {
1005     if (errno == ETIMEDOUT) {
1006       // Timed out we're done.
1007       timed_out = true;
1008     } else if ((errno == EAGAIN) || (errno == EINTR)) {
1009       // A signal or ConditionVariable::Signal/Broadcast has come in.
1010     } else {
1011       PLOG(FATAL) << "timed futex wait failed for " << name_;
1012     }
1013   }
1014   guard_.ExclusiveLock(self);
1015   CHECK_GE(num_waiters_, 0);
1016   num_waiters_--;
1017   // We awoke and so no longer require awakes from the guard_'s unlock.
1018   CHECK_GE(guard_.num_contenders_.LoadRelaxed(), 0);
1019   guard_.num_contenders_--;
1020 #else
1021 #if !defined(__APPLE__)
1022   int clock = CLOCK_MONOTONIC;
1023 #else
1024   int clock = CLOCK_REALTIME;
1025 #endif
1026   pid_t old_owner = guard_.GetExclusiveOwnerTid();
1027   guard_.exclusive_owner_.StoreRelaxed(0);
1028   guard_.recursion_count_ = 0;
1029   timespec ts;
1030   InitTimeSpec(true, clock, ms, ns, &ts);
1031   int rc = TEMP_FAILURE_RETRY(pthread_cond_timedwait(&cond_, &guard_.mutex_, &ts));
1032   if (rc == ETIMEDOUT) {
1033     timed_out = true;
1034   } else if (rc != 0) {
1035     errno = rc;
1036     PLOG(FATAL) << "TimedWait failed for " << name_;
1037   }
1038   guard_.exclusive_owner_.StoreRelaxed(old_owner);
1039 #endif
1040   guard_.recursion_count_ = old_recursion_count;
1041   return timed_out;
1042 }
1043 
Init()1044 void Locks::Init() {
1045   if (logging_lock_ != nullptr) {
1046     // Already initialized.
1047     if (kRuntimeISA == InstructionSet::kX86 || kRuntimeISA == InstructionSet::kX86_64) {
1048       DCHECK(modify_ldt_lock_ != nullptr);
1049     } else {
1050       DCHECK(modify_ldt_lock_ == nullptr);
1051     }
1052     DCHECK(abort_lock_ != nullptr);
1053     DCHECK(alloc_tracker_lock_ != nullptr);
1054     DCHECK(allocated_monitor_ids_lock_ != nullptr);
1055     DCHECK(allocated_thread_ids_lock_ != nullptr);
1056     DCHECK(breakpoint_lock_ != nullptr);
1057     DCHECK(classlinker_classes_lock_ != nullptr);
1058     DCHECK(deoptimization_lock_ != nullptr);
1059     DCHECK(heap_bitmap_lock_ != nullptr);
1060     DCHECK(oat_file_manager_lock_ != nullptr);
1061     DCHECK(verifier_deps_lock_ != nullptr);
1062     DCHECK(host_dlopen_handles_lock_ != nullptr);
1063     DCHECK(intern_table_lock_ != nullptr);
1064     DCHECK(jni_function_table_lock_ != nullptr);
1065     DCHECK(jni_libraries_lock_ != nullptr);
1066     DCHECK(logging_lock_ != nullptr);
1067     DCHECK(mutator_lock_ != nullptr);
1068     DCHECK(profiler_lock_ != nullptr);
1069     DCHECK(cha_lock_ != nullptr);
1070     DCHECK(subtype_check_lock_ != nullptr);
1071     DCHECK(thread_list_lock_ != nullptr);
1072     DCHECK(thread_suspend_count_lock_ != nullptr);
1073     DCHECK(trace_lock_ != nullptr);
1074     DCHECK(unexpected_signal_lock_ != nullptr);
1075     DCHECK(user_code_suspension_lock_ != nullptr);
1076     DCHECK(dex_lock_ != nullptr);
1077     DCHECK(native_debug_interface_lock_ != nullptr);
1078   } else {
1079     // Create global locks in level order from highest lock level to lowest.
1080     LockLevel current_lock_level = kInstrumentEntrypointsLock;
1081     DCHECK(instrument_entrypoints_lock_ == nullptr);
1082     instrument_entrypoints_lock_ = new Mutex("instrument entrypoint lock", current_lock_level);
1083 
1084     #define UPDATE_CURRENT_LOCK_LEVEL(new_level) \
1085       if ((new_level) >= current_lock_level) { \
1086         /* Do not use CHECKs or FATAL here, abort_lock_ is not setup yet. */ \
1087         fprintf(stderr, "New local level %d is not less than current level %d\n", \
1088                 new_level, current_lock_level); \
1089         exit(1); \
1090       } \
1091       current_lock_level = new_level;
1092 
1093     UPDATE_CURRENT_LOCK_LEVEL(kUserCodeSuspensionLock);
1094     DCHECK(user_code_suspension_lock_ == nullptr);
1095     user_code_suspension_lock_ = new Mutex("user code suspension lock", current_lock_level);
1096 
1097     UPDATE_CURRENT_LOCK_LEVEL(kMutatorLock);
1098     DCHECK(mutator_lock_ == nullptr);
1099     mutator_lock_ = new MutatorMutex("mutator lock", current_lock_level);
1100 
1101     UPDATE_CURRENT_LOCK_LEVEL(kHeapBitmapLock);
1102     DCHECK(heap_bitmap_lock_ == nullptr);
1103     heap_bitmap_lock_ = new ReaderWriterMutex("heap bitmap lock", current_lock_level);
1104 
1105     UPDATE_CURRENT_LOCK_LEVEL(kTraceLock);
1106     DCHECK(trace_lock_ == nullptr);
1107     trace_lock_ = new Mutex("trace lock", current_lock_level);
1108 
1109     UPDATE_CURRENT_LOCK_LEVEL(kRuntimeShutdownLock);
1110     DCHECK(runtime_shutdown_lock_ == nullptr);
1111     runtime_shutdown_lock_ = new Mutex("runtime shutdown lock", current_lock_level);
1112 
1113     UPDATE_CURRENT_LOCK_LEVEL(kProfilerLock);
1114     DCHECK(profiler_lock_ == nullptr);
1115     profiler_lock_ = new Mutex("profiler lock", current_lock_level);
1116 
1117     UPDATE_CURRENT_LOCK_LEVEL(kDeoptimizationLock);
1118     DCHECK(deoptimization_lock_ == nullptr);
1119     deoptimization_lock_ = new Mutex("Deoptimization lock", current_lock_level);
1120 
1121     UPDATE_CURRENT_LOCK_LEVEL(kAllocTrackerLock);
1122     DCHECK(alloc_tracker_lock_ == nullptr);
1123     alloc_tracker_lock_ = new Mutex("AllocTracker lock", current_lock_level);
1124 
1125     UPDATE_CURRENT_LOCK_LEVEL(kThreadListLock);
1126     DCHECK(thread_list_lock_ == nullptr);
1127     thread_list_lock_ = new Mutex("thread list lock", current_lock_level);
1128 
1129     UPDATE_CURRENT_LOCK_LEVEL(kJniLoadLibraryLock);
1130     DCHECK(jni_libraries_lock_ == nullptr);
1131     jni_libraries_lock_ = new Mutex("JNI shared libraries map lock", current_lock_level);
1132 
1133     UPDATE_CURRENT_LOCK_LEVEL(kBreakpointLock);
1134     DCHECK(breakpoint_lock_ == nullptr);
1135     breakpoint_lock_ = new ReaderWriterMutex("breakpoint lock", current_lock_level);
1136 
1137     UPDATE_CURRENT_LOCK_LEVEL(kSubtypeCheckLock);
1138     DCHECK(subtype_check_lock_ == nullptr);
1139     subtype_check_lock_ = new Mutex("SubtypeCheck lock", current_lock_level);
1140 
1141     UPDATE_CURRENT_LOCK_LEVEL(kCHALock);
1142     DCHECK(cha_lock_ == nullptr);
1143     cha_lock_ = new Mutex("CHA lock", current_lock_level);
1144 
1145     UPDATE_CURRENT_LOCK_LEVEL(kClassLinkerClassesLock);
1146     DCHECK(classlinker_classes_lock_ == nullptr);
1147     classlinker_classes_lock_ = new ReaderWriterMutex("ClassLinker classes lock",
1148                                                       current_lock_level);
1149 
1150     UPDATE_CURRENT_LOCK_LEVEL(kMonitorPoolLock);
1151     DCHECK(allocated_monitor_ids_lock_ == nullptr);
1152     allocated_monitor_ids_lock_ =  new Mutex("allocated monitor ids lock", current_lock_level);
1153 
1154     UPDATE_CURRENT_LOCK_LEVEL(kAllocatedThreadIdsLock);
1155     DCHECK(allocated_thread_ids_lock_ == nullptr);
1156     allocated_thread_ids_lock_ =  new Mutex("allocated thread ids lock", current_lock_level);
1157 
1158     if (kRuntimeISA == InstructionSet::kX86 || kRuntimeISA == InstructionSet::kX86_64) {
1159       UPDATE_CURRENT_LOCK_LEVEL(kModifyLdtLock);
1160       DCHECK(modify_ldt_lock_ == nullptr);
1161       modify_ldt_lock_ = new Mutex("modify_ldt lock", current_lock_level);
1162     }
1163 
1164     UPDATE_CURRENT_LOCK_LEVEL(kDexLock);
1165     DCHECK(dex_lock_ == nullptr);
1166     dex_lock_ = new ReaderWriterMutex("ClassLinker dex lock", current_lock_level);
1167 
1168     UPDATE_CURRENT_LOCK_LEVEL(kOatFileManagerLock);
1169     DCHECK(oat_file_manager_lock_ == nullptr);
1170     oat_file_manager_lock_ = new ReaderWriterMutex("OatFile manager lock", current_lock_level);
1171 
1172     UPDATE_CURRENT_LOCK_LEVEL(kVerifierDepsLock);
1173     DCHECK(verifier_deps_lock_ == nullptr);
1174     verifier_deps_lock_ = new ReaderWriterMutex("verifier deps lock", current_lock_level);
1175 
1176     UPDATE_CURRENT_LOCK_LEVEL(kHostDlOpenHandlesLock);
1177     DCHECK(host_dlopen_handles_lock_ == nullptr);
1178     host_dlopen_handles_lock_ = new Mutex("host dlopen handles lock", current_lock_level);
1179 
1180     UPDATE_CURRENT_LOCK_LEVEL(kInternTableLock);
1181     DCHECK(intern_table_lock_ == nullptr);
1182     intern_table_lock_ = new Mutex("InternTable lock", current_lock_level);
1183 
1184     UPDATE_CURRENT_LOCK_LEVEL(kReferenceProcessorLock);
1185     DCHECK(reference_processor_lock_ == nullptr);
1186     reference_processor_lock_ = new Mutex("ReferenceProcessor lock", current_lock_level);
1187 
1188     UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueClearedReferencesLock);
1189     DCHECK(reference_queue_cleared_references_lock_ == nullptr);
1190     reference_queue_cleared_references_lock_ = new Mutex("ReferenceQueue cleared references lock", current_lock_level);
1191 
1192     UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueWeakReferencesLock);
1193     DCHECK(reference_queue_weak_references_lock_ == nullptr);
1194     reference_queue_weak_references_lock_ = new Mutex("ReferenceQueue cleared references lock", current_lock_level);
1195 
1196     UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueFinalizerReferencesLock);
1197     DCHECK(reference_queue_finalizer_references_lock_ == nullptr);
1198     reference_queue_finalizer_references_lock_ = new Mutex("ReferenceQueue finalizer references lock", current_lock_level);
1199 
1200     UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueuePhantomReferencesLock);
1201     DCHECK(reference_queue_phantom_references_lock_ == nullptr);
1202     reference_queue_phantom_references_lock_ = new Mutex("ReferenceQueue phantom references lock", current_lock_level);
1203 
1204     UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueSoftReferencesLock);
1205     DCHECK(reference_queue_soft_references_lock_ == nullptr);
1206     reference_queue_soft_references_lock_ = new Mutex("ReferenceQueue soft references lock", current_lock_level);
1207 
1208     UPDATE_CURRENT_LOCK_LEVEL(kJniGlobalsLock);
1209     DCHECK(jni_globals_lock_ == nullptr);
1210     jni_globals_lock_ =
1211         new ReaderWriterMutex("JNI global reference table lock", current_lock_level);
1212 
1213     UPDATE_CURRENT_LOCK_LEVEL(kJniWeakGlobalsLock);
1214     DCHECK(jni_weak_globals_lock_ == nullptr);
1215     jni_weak_globals_lock_ = new Mutex("JNI weak global reference table lock", current_lock_level);
1216 
1217     UPDATE_CURRENT_LOCK_LEVEL(kJniFunctionTableLock);
1218     DCHECK(jni_function_table_lock_ == nullptr);
1219     jni_function_table_lock_ = new Mutex("JNI function table lock", current_lock_level);
1220 
1221     UPDATE_CURRENT_LOCK_LEVEL(kNativeDebugInterfaceLock);
1222     DCHECK(native_debug_interface_lock_ == nullptr);
1223     native_debug_interface_lock_ = new Mutex("Native debug interface lock", current_lock_level);
1224 
1225     UPDATE_CURRENT_LOCK_LEVEL(kAbortLock);
1226     DCHECK(abort_lock_ == nullptr);
1227     abort_lock_ = new Mutex("abort lock", current_lock_level, true);
1228 
1229     UPDATE_CURRENT_LOCK_LEVEL(kThreadSuspendCountLock);
1230     DCHECK(thread_suspend_count_lock_ == nullptr);
1231     thread_suspend_count_lock_ = new Mutex("thread suspend count lock", current_lock_level);
1232 
1233     UPDATE_CURRENT_LOCK_LEVEL(kUnexpectedSignalLock);
1234     DCHECK(unexpected_signal_lock_ == nullptr);
1235     unexpected_signal_lock_ = new Mutex("unexpected signal lock", current_lock_level, true);
1236 
1237     UPDATE_CURRENT_LOCK_LEVEL(kLoggingLock);
1238     DCHECK(logging_lock_ == nullptr);
1239     logging_lock_ = new Mutex("logging lock", current_lock_level, true);
1240 
1241     #undef UPDATE_CURRENT_LOCK_LEVEL
1242 
1243     // List of mutexes that we may hold when accessing a weak ref.
1244     AddToExpectedMutexesOnWeakRefAccess(dex_lock_, /*need_lock*/ false);
1245     AddToExpectedMutexesOnWeakRefAccess(classlinker_classes_lock_, /*need_lock*/ false);
1246     AddToExpectedMutexesOnWeakRefAccess(jni_libraries_lock_, /*need_lock*/ false);
1247 
1248     InitConditions();
1249   }
1250 }
1251 
InitConditions()1252 void Locks::InitConditions() {
1253   thread_exit_cond_ = new ConditionVariable("thread exit condition variable", *thread_list_lock_);
1254 }
1255 
SetClientCallback(ClientCallback * safe_to_call_abort_cb)1256 void Locks::SetClientCallback(ClientCallback* safe_to_call_abort_cb) {
1257   safe_to_call_abort_callback.StoreRelease(safe_to_call_abort_cb);
1258 }
1259 
1260 // Helper to allow checking shutdown while ignoring locking requirements.
IsSafeToCallAbortRacy()1261 bool Locks::IsSafeToCallAbortRacy() {
1262   Locks::ClientCallback* safe_to_call_abort_cb = safe_to_call_abort_callback.LoadAcquire();
1263   return safe_to_call_abort_cb != nullptr && safe_to_call_abort_cb();
1264 }
1265 
AddToExpectedMutexesOnWeakRefAccess(BaseMutex * mutex,bool need_lock)1266 void Locks::AddToExpectedMutexesOnWeakRefAccess(BaseMutex* mutex, bool need_lock) {
1267   if (need_lock) {
1268     ScopedExpectedMutexesOnWeakRefAccessLock mu(mutex);
1269     mutex->SetShouldRespondToEmptyCheckpointRequest(true);
1270     expected_mutexes_on_weak_ref_access_.push_back(mutex);
1271   } else {
1272     mutex->SetShouldRespondToEmptyCheckpointRequest(true);
1273     expected_mutexes_on_weak_ref_access_.push_back(mutex);
1274   }
1275 }
1276 
RemoveFromExpectedMutexesOnWeakRefAccess(BaseMutex * mutex,bool need_lock)1277 void Locks::RemoveFromExpectedMutexesOnWeakRefAccess(BaseMutex* mutex, bool need_lock) {
1278   if (need_lock) {
1279     ScopedExpectedMutexesOnWeakRefAccessLock mu(mutex);
1280     mutex->SetShouldRespondToEmptyCheckpointRequest(false);
1281     std::vector<BaseMutex*>& list = expected_mutexes_on_weak_ref_access_;
1282     auto it = std::find(list.begin(), list.end(), mutex);
1283     DCHECK(it != list.end());
1284     list.erase(it);
1285   } else {
1286     mutex->SetShouldRespondToEmptyCheckpointRequest(false);
1287     std::vector<BaseMutex*>& list = expected_mutexes_on_weak_ref_access_;
1288     auto it = std::find(list.begin(), list.end(), mutex);
1289     DCHECK(it != list.end());
1290     list.erase(it);
1291   }
1292 }
1293 
IsExpectedOnWeakRefAccess(BaseMutex * mutex)1294 bool Locks::IsExpectedOnWeakRefAccess(BaseMutex* mutex) {
1295   ScopedExpectedMutexesOnWeakRefAccessLock mu(mutex);
1296   std::vector<BaseMutex*>& list = expected_mutexes_on_weak_ref_access_;
1297   return std::find(list.begin(), list.end(), mutex) != list.end();
1298 }
1299 
1300 }  // namespace art
1301