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
30namespace art {
31
32Mutex* Locks::abort_lock_ = nullptr;
33Mutex* Locks::alloc_tracker_lock_ = nullptr;
34Mutex* Locks::allocated_monitor_ids_lock_ = nullptr;
35Mutex* Locks::allocated_thread_ids_lock_ = nullptr;
36ReaderWriterMutex* Locks::breakpoint_lock_ = nullptr;
37ReaderWriterMutex* Locks::classlinker_classes_lock_ = nullptr;
38Mutex* Locks::deoptimization_lock_ = nullptr;
39ReaderWriterMutex* Locks::heap_bitmap_lock_ = nullptr;
40Mutex* Locks::instrument_entrypoints_lock_ = nullptr;
41Mutex* Locks::intern_table_lock_ = nullptr;
42Mutex* Locks::logging_lock_ = nullptr;
43Mutex* Locks::mem_maps_lock_ = nullptr;
44Mutex* Locks::modify_ldt_lock_ = nullptr;
45ReaderWriterMutex* Locks::mutator_lock_ = nullptr;
46Mutex* Locks::profiler_lock_ = nullptr;
47Mutex* Locks::reference_processor_lock_ = nullptr;
48Mutex* Locks::reference_queue_cleared_references_lock_ = nullptr;
49Mutex* Locks::reference_queue_finalizer_references_lock_ = nullptr;
50Mutex* Locks::reference_queue_phantom_references_lock_ = nullptr;
51Mutex* Locks::reference_queue_soft_references_lock_ = nullptr;
52Mutex* Locks::reference_queue_weak_references_lock_ = nullptr;
53Mutex* Locks::runtime_shutdown_lock_ = nullptr;
54Mutex* Locks::thread_list_lock_ = nullptr;
55Mutex* Locks::thread_list_suspend_thread_lock_ = nullptr;
56Mutex* Locks::thread_suspend_count_lock_ = nullptr;
57Mutex* Locks::trace_lock_ = nullptr;
58Mutex* Locks::unexpected_signal_lock_ = nullptr;
59
60struct 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;
65  AllMutexData() : all_mutexes(NULL) {}
66};
67static struct AllMutexData gAllMutexData[kAllMutexDataSize];
68
69#if ART_USE_FUTEXES
70static 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
85class ScopedAllMutexesLock {
86 public:
87  explicit ScopedAllMutexesLock(const BaseMutex* mutex) : mutex_(mutex) {
88    while (!gAllMutexData->all_mutexes_guard.CompareExchangeWeakAcquire(0, mutex)) {
89      NanoSleep(100);
90    }
91  }
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
101BaseMutex::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
114BaseMutex::~BaseMutex() {
115  if (kLogLockContentions) {
116    ScopedAllMutexesLock mu(this);
117    gAllMutexData->all_mutexes->erase(this);
118  }
119}
120
121void 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
150void 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
175void BaseMutex::ContentionLogData::AddToWaitTime(uint64_t value) {
176  if (kLogLockContentions) {
177    // Atomically add value to wait_time.
178    wait_time.FetchAndAddSequentiallyConsistent(value);
179  }
180}
181
182void 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
208void 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
268Mutex::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.
280static bool IsShuttingDown() NO_THREAD_SAFETY_ANALYSIS {
281  Runtime* runtime = Runtime::Current();
282  return runtime == nullptr || runtime->IsShuttingDownLocked();
283}
284
285Mutex::~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
313void 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
356bool 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
397void 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
445void 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
454std::ostream& operator<<(std::ostream& os, const Mutex& mu) {
455  mu.Dump(os);
456  return os;
457}
458
459ReaderWriterMutex::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
471ReaderWriterMutex::~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
492void 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
526void 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
561bool 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
615bool 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
644bool 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
655void 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
668std::ostream& operator<<(std::ostream& os, const ReaderWriterMutex& mu) {
669  mu.Dump(os);
670  return os;
671}
672
673ConditionVariable::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
689ConditionVariable::~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
711void 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
739void 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
756void ConditionVariable::Wait(Thread* self) {
757  guard_.CheckSafeToWait(self);
758  WaitHoldingLocks(self);
759}
760
761void 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
796void 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
846void 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