/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "mutex.h"
#include <errno.h>
#include <sys/time.h>
#include "atomic.h"
#include "base/logging.h"
#include "mutex-inl.h"
#include "runtime.h"
#include "scoped_thread_state_change.h"
#include "thread-inl.h"
#include "utils.h"
namespace art {
Mutex* Locks::abort_lock_ = nullptr;
Mutex* Locks::alloc_tracker_lock_ = nullptr;
Mutex* Locks::allocated_monitor_ids_lock_ = nullptr;
Mutex* Locks::allocated_thread_ids_lock_ = nullptr;
ReaderWriterMutex* Locks::breakpoint_lock_ = nullptr;
ReaderWriterMutex* Locks::classlinker_classes_lock_ = nullptr;
Mutex* Locks::deoptimization_lock_ = nullptr;
ReaderWriterMutex* Locks::heap_bitmap_lock_ = nullptr;
Mutex* Locks::instrument_entrypoints_lock_ = nullptr;
Mutex* Locks::intern_table_lock_ = nullptr;
Mutex* Locks::logging_lock_ = nullptr;
Mutex* Locks::mem_maps_lock_ = nullptr;
Mutex* Locks::modify_ldt_lock_ = nullptr;
ReaderWriterMutex* Locks::mutator_lock_ = nullptr;
Mutex* Locks::profiler_lock_ = nullptr;
Mutex* Locks::reference_processor_lock_ = nullptr;
Mutex* Locks::reference_queue_cleared_references_lock_ = nullptr;
Mutex* Locks::reference_queue_finalizer_references_lock_ = nullptr;
Mutex* Locks::reference_queue_phantom_references_lock_ = nullptr;
Mutex* Locks::reference_queue_soft_references_lock_ = nullptr;
Mutex* Locks::reference_queue_weak_references_lock_ = nullptr;
Mutex* Locks::runtime_shutdown_lock_ = nullptr;
Mutex* Locks::thread_list_lock_ = nullptr;
Mutex* Locks::thread_list_suspend_thread_lock_ = nullptr;
Mutex* Locks::thread_suspend_count_lock_ = nullptr;
Mutex* Locks::trace_lock_ = nullptr;
Mutex* Locks::unexpected_signal_lock_ = nullptr;
struct AllMutexData {
// A guard for all_mutexes_ that's not a mutex (Mutexes must CAS to acquire and busy wait).
Atomic<const BaseMutex*> all_mutexes_guard;
// All created mutexes guarded by all_mutexes_guard_.
std::set<BaseMutex*>* all_mutexes;
AllMutexData() : all_mutexes(NULL) {}
};
static struct AllMutexData gAllMutexData[kAllMutexDataSize];
#if ART_USE_FUTEXES
static bool ComputeRelativeTimeSpec(timespec* result_ts, const timespec& lhs, const timespec& rhs) {
const int32_t one_sec = 1000 * 1000 * 1000; // one second in nanoseconds.
result_ts->tv_sec = lhs.tv_sec - rhs.tv_sec;
result_ts->tv_nsec = lhs.tv_nsec - rhs.tv_nsec;
if (result_ts->tv_nsec < 0) {
result_ts->tv_sec--;
result_ts->tv_nsec += one_sec;
} else if (result_ts->tv_nsec > one_sec) {
result_ts->tv_sec++;
result_ts->tv_nsec -= one_sec;
}
return result_ts->tv_sec < 0;
}
#endif
class ScopedAllMutexesLock {
public:
explicit ScopedAllMutexesLock(const BaseMutex* mutex) : mutex_(mutex) {
while (!gAllMutexData->all_mutexes_guard.CompareExchangeWeakAcquire(0, mutex)) {
NanoSleep(100);
}
}
~ScopedAllMutexesLock() {
while (!gAllMutexData->all_mutexes_guard.CompareExchangeWeakRelease(mutex_, 0)) {
NanoSleep(100);
}
}
private:
const BaseMutex* const mutex_;
};
BaseMutex::BaseMutex(const char* name, LockLevel level) : level_(level), name_(name) {
if (kLogLockContentions) {
ScopedAllMutexesLock mu(this);
std::set<BaseMutex*>** all_mutexes_ptr = &gAllMutexData->all_mutexes;
if (*all_mutexes_ptr == NULL) {
// We leak the global set of all mutexes to avoid ordering issues in global variable
// construction/destruction.
*all_mutexes_ptr = new std::set<BaseMutex*>();
}
(*all_mutexes_ptr)->insert(this);
}
}
BaseMutex::~BaseMutex() {
if (kLogLockContentions) {
ScopedAllMutexesLock mu(this);
gAllMutexData->all_mutexes->erase(this);
}
}
void BaseMutex::DumpAll(std::ostream& os) {
if (kLogLockContentions) {
os << "Mutex logging:\n";
ScopedAllMutexesLock mu(reinterpret_cast<const BaseMutex*>(-1));
std::set<BaseMutex*>* all_mutexes = gAllMutexData->all_mutexes;
if (all_mutexes == NULL) {
// No mutexes have been created yet during at startup.
return;
}
typedef std::set<BaseMutex*>::const_iterator It;
os << "(Contended)\n";
for (It it = all_mutexes->begin(); it != all_mutexes->end(); ++it) {
BaseMutex* mutex = *it;
if (mutex->HasEverContended()) {
mutex->Dump(os);
os << "\n";
}
}
os << "(Never contented)\n";
for (It it = all_mutexes->begin(); it != all_mutexes->end(); ++it) {
BaseMutex* mutex = *it;
if (!mutex->HasEverContended()) {
mutex->Dump(os);
os << "\n";
}
}
}
}
void BaseMutex::CheckSafeToWait(Thread* self) {
if (self == NULL) {
CheckUnattachedThread(level_);
return;
}
if (kDebugLocking) {
CHECK(self->GetHeldMutex(level_) == this || level_ == kMonitorLock)
<< "Waiting on unacquired mutex: " << name_;
bool bad_mutexes_held = false;
for (int i = kLockLevelCount - 1; i >= 0; --i) {
if (i != level_) {
BaseMutex* held_mutex = self->GetHeldMutex(static_cast<LockLevel>(i));
// We expect waits to happen while holding the thread list suspend thread lock.
if (held_mutex != NULL && i != kThreadListSuspendThreadLock) {
LOG(ERROR) << "Holding \"" << held_mutex->name_ << "\" "
<< "(level " << LockLevel(i) << ") while performing wait on "
<< "\"" << name_ << "\" (level " << level_ << ")";
bad_mutexes_held = true;
}
}
}
CHECK(!bad_mutexes_held);
}
}
void BaseMutex::ContentionLogData::AddToWaitTime(uint64_t value) {
if (kLogLockContentions) {
// Atomically add value to wait_time.
wait_time.FetchAndAddSequentiallyConsistent(value);
}
}
void BaseMutex::RecordContention(uint64_t blocked_tid,
uint64_t owner_tid,
uint64_t nano_time_blocked) {
if (kLogLockContentions) {
ContentionLogData* data = contention_log_data_;
++(data->contention_count);
data->AddToWaitTime(nano_time_blocked);
ContentionLogEntry* log = data->contention_log;
// This code is intentionally racy as it is only used for diagnostics.
uint32_t slot = data->cur_content_log_entry.LoadRelaxed();
if (log[slot].blocked_tid == blocked_tid &&
log[slot].owner_tid == blocked_tid) {
++log[slot].count;
} else {
uint32_t new_slot;
do {
slot = data->cur_content_log_entry.LoadRelaxed();
new_slot = (slot + 1) % kContentionLogSize;
} while (!data->cur_content_log_entry.CompareExchangeWeakRelaxed(slot, new_slot));
log[new_slot].blocked_tid = blocked_tid;
log[new_slot].owner_tid = owner_tid;
log[new_slot].count.StoreRelaxed(1);
}
}
}
void BaseMutex::DumpContention(std::ostream& os) const {
if (kLogLockContentions) {
const ContentionLogData* data = contention_log_data_;
const ContentionLogEntry* log = data->contention_log;
uint64_t wait_time = data->wait_time.LoadRelaxed();
uint32_t contention_count = data->contention_count.LoadRelaxed();
if (contention_count == 0) {
os << "never contended";
} else {
os << "contended " << contention_count
<< " total wait of contender " << PrettyDuration(wait_time)
<< " average " << PrettyDuration(wait_time / contention_count);
SafeMap<uint64_t, size_t> most_common_blocker;
SafeMap<uint64_t, size_t> most_common_blocked;
for (size_t i = 0; i < kContentionLogSize; ++i) {
uint64_t blocked_tid = log[i].blocked_tid;
uint64_t owner_tid = log[i].owner_tid;
uint32_t count = log[i].count.LoadRelaxed();
if (count > 0) {
auto it = most_common_blocked.find(blocked_tid);
if (it != most_common_blocked.end()) {
most_common_blocked.Overwrite(blocked_tid, it->second + count);
} else {
most_common_blocked.Put(blocked_tid, count);
}
it = most_common_blocker.find(owner_tid);
if (it != most_common_blocker.end()) {
most_common_blocker.Overwrite(owner_tid, it->second + count);
} else {
most_common_blocker.Put(owner_tid, count);
}
}
}
uint64_t max_tid = 0;
size_t max_tid_count = 0;
for (const auto& pair : most_common_blocked) {
if (pair.second > max_tid_count) {
max_tid = pair.first;
max_tid_count = pair.second;
}
}
if (max_tid != 0) {
os << " sample shows most blocked tid=" << max_tid;
}
max_tid = 0;
max_tid_count = 0;
for (const auto& pair : most_common_blocker) {
if (pair.second > max_tid_count) {
max_tid = pair.first;
max_tid_count = pair.second;
}
}
if (max_tid != 0) {
os << " sample shows tid=" << max_tid << " owning during this time";
}
}
}
}
Mutex::Mutex(const char* name, LockLevel level, bool recursive)
: BaseMutex(name, level), recursive_(recursive), recursion_count_(0) {
#if ART_USE_FUTEXES
DCHECK_EQ(0, state_.LoadRelaxed());
DCHECK_EQ(0, num_contenders_.LoadRelaxed());
#else
CHECK_MUTEX_CALL(pthread_mutex_init, (&mutex_, nullptr));
#endif
exclusive_owner_ = 0;
}
// Helper to ignore the lock requirement.
static bool IsShuttingDown() NO_THREAD_SAFETY_ANALYSIS {
Runtime* runtime = Runtime::Current();
return runtime == nullptr || runtime->IsShuttingDownLocked();
}
Mutex::~Mutex() {
bool shutting_down = IsShuttingDown();
#if ART_USE_FUTEXES
if (state_.LoadRelaxed() != 0) {
LOG(shutting_down ? WARNING : FATAL) << "destroying mutex with owner: "
<< exclusive_owner_;
} else {
if (exclusive_owner_ != 0) {
LOG(shutting_down ? WARNING : FATAL) << "unexpectedly found an owner on unlocked mutex "
<< name_;
}
if (num_contenders_.LoadSequentiallyConsistent() != 0) {
LOG(shutting_down ? WARNING : FATAL) << "unexpectedly found a contender on mutex " << name_;
}
}
#else
// We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
// may still be using locks.
int rc = pthread_mutex_destroy(&mutex_);
if (rc != 0) {
errno = rc;
// TODO: should we just not log at all if shutting down? this could be the logging mutex!
MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
PLOG(shutting_down ? WARNING : FATAL) << "pthread_mutex_destroy failed for " << name_;
}
#endif
}
void Mutex::ExclusiveLock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
if (kDebugLocking && !recursive_) {
AssertNotHeld(self);
}
if (!recursive_ || !IsExclusiveHeld(self)) {
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_.LoadRelaxed();
if (LIKELY(cur_state == 0)) {
// Change state from 0 to 1 and impose load/store ordering appropriate for lock acquisition.
done = state_.CompareExchangeWeakAcquire(0 /* cur_state */, 1 /* new state */);
} else {
// Failed to acquire, hang up.
ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
num_contenders_++;
if (futex(state_.Address(), FUTEX_WAIT, 1, NULL, NULL, 0) != 0) {
// EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
// We don't use TEMP_FAILURE_RETRY so we can intentionally retry to acquire the lock.
if ((errno != EAGAIN) && (errno != EINTR)) {
PLOG(FATAL) << "futex wait failed for " << name_;
}
}
num_contenders_--;
}
} while (!done);
DCHECK_EQ(state_.LoadRelaxed(), 1);
#else
CHECK_MUTEX_CALL(pthread_mutex_lock, (&mutex_));
#endif
DCHECK_EQ(exclusive_owner_, 0U);
exclusive_owner_ = SafeGetTid(self);
RegisterAsLocked(self);
}
recursion_count_++;
if (kDebugLocking) {
CHECK(recursion_count_ == 1 || recursive_) << "Unexpected recursion count on mutex: "
<< name_ << " " << recursion_count_;
AssertHeld(self);
}
}
bool Mutex::ExclusiveTryLock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
if (kDebugLocking && !recursive_) {
AssertNotHeld(self);
}
if (!recursive_ || !IsExclusiveHeld(self)) {
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_.LoadRelaxed();
if (cur_state == 0) {
// Change state from 0 to 1 and impose load/store ordering appropriate for lock acquisition.
done = state_.CompareExchangeWeakAcquire(0 /* cur_state */, 1 /* new state */);
} else {
return false;
}
} while (!done);
DCHECK_EQ(state_.LoadRelaxed(), 1);
#else
int result = pthread_mutex_trylock(&mutex_);
if (result == EBUSY) {
return false;
}
if (result != 0) {
errno = result;
PLOG(FATAL) << "pthread_mutex_trylock failed for " << name_;
}
#endif
DCHECK_EQ(exclusive_owner_, 0U);
exclusive_owner_ = SafeGetTid(self);
RegisterAsLocked(self);
}
recursion_count_++;
if (kDebugLocking) {
CHECK(recursion_count_ == 1 || recursive_) << "Unexpected recursion count on mutex: "
<< name_ << " " << recursion_count_;
AssertHeld(self);
}
return true;
}
void Mutex::ExclusiveUnlock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
AssertHeld(self);
DCHECK_NE(exclusive_owner_, 0U);
recursion_count_--;
if (!recursive_ || recursion_count_ == 0) {
if (kDebugLocking) {
CHECK(recursion_count_ == 0 || recursive_) << "Unexpected recursion count on mutex: "
<< name_ << " " << recursion_count_;
}
RegisterAsUnlocked(self);
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_.LoadRelaxed();
if (LIKELY(cur_state == 1)) {
// We're no longer the owner.
exclusive_owner_ = 0;
// Change state to 0 and impose load/store ordering appropriate for lock release.
// Note, the relaxed loads below musn't reorder before the CompareExchange.
// TODO: the ordering here is non-trivial as state is split across 3 fields, fix by placing
// a status bit into the state on contention.
done = state_.CompareExchangeWeakSequentiallyConsistent(cur_state, 0 /* new state */);
if (LIKELY(done)) { // Spurious fail?
// Wake a contender.
if (UNLIKELY(num_contenders_.LoadRelaxed() > 0)) {
futex(state_.Address(), FUTEX_WAKE, 1, NULL, NULL, 0);
}
}
} else {
// Logging acquires the logging lock, avoid infinite recursion in that case.
if (this != Locks::logging_lock_) {
LOG(FATAL) << "Unexpected state_ in unlock " << cur_state << " for " << name_;
} else {
LogMessageData data(__FILE__, __LINE__, INTERNAL_FATAL, -1);
LogMessage::LogLine(data, StringPrintf("Unexpected state_ %d in unlock for %s",
cur_state, name_).c_str());
_exit(1);
}
}
} while (!done);
#else
exclusive_owner_ = 0;
CHECK_MUTEX_CALL(pthread_mutex_unlock, (&mutex_));
#endif
}
}
void Mutex::Dump(std::ostream& os) const {
os << (recursive_ ? "recursive " : "non-recursive ")
<< name_
<< " level=" << static_cast<int>(level_)
<< " rec=" << recursion_count_
<< " owner=" << GetExclusiveOwnerTid() << " ";
DumpContention(os);
}
std::ostream& operator<<(std::ostream& os, const Mutex& mu) {
mu.Dump(os);
return os;
}
ReaderWriterMutex::ReaderWriterMutex(const char* name, LockLevel level)
: BaseMutex(name, level)
#if ART_USE_FUTEXES
, state_(0), num_pending_readers_(0), num_pending_writers_(0)
#endif
{ // NOLINT(whitespace/braces)
#if !ART_USE_FUTEXES
CHECK_MUTEX_CALL(pthread_rwlock_init, (&rwlock_, nullptr));
#endif
exclusive_owner_ = 0;
}
ReaderWriterMutex::~ReaderWriterMutex() {
#if ART_USE_FUTEXES
CHECK_EQ(state_.LoadRelaxed(), 0);
CHECK_EQ(exclusive_owner_, 0U);
CHECK_EQ(num_pending_readers_.LoadRelaxed(), 0);
CHECK_EQ(num_pending_writers_.LoadRelaxed(), 0);
#else
// We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
// may still be using locks.
int rc = pthread_rwlock_destroy(&rwlock_);
if (rc != 0) {
errno = rc;
// TODO: should we just not log at all if shutting down? this could be the logging mutex!
MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
Runtime* runtime = Runtime::Current();
bool shutting_down = runtime == NULL || runtime->IsShuttingDownLocked();
PLOG(shutting_down ? WARNING : FATAL) << "pthread_rwlock_destroy failed for " << name_;
}
#endif
}
void ReaderWriterMutex::ExclusiveLock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
AssertNotExclusiveHeld(self);
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_.LoadRelaxed();
if (LIKELY(cur_state == 0)) {
// Change state from 0 to -1 and impose load/store ordering appropriate for lock acquisition.
done = state_.CompareExchangeWeakAcquire(0 /* cur_state*/, -1 /* new state */);
} else {
// Failed to acquire, hang up.
ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
++num_pending_writers_;
if (futex(state_.Address(), FUTEX_WAIT, cur_state, NULL, NULL, 0) != 0) {
// EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
// We don't use TEMP_FAILURE_RETRY so we can intentionally retry to acquire the lock.
if ((errno != EAGAIN) && (errno != EINTR)) {
PLOG(FATAL) << "futex wait failed for " << name_;
}
}
--num_pending_writers_;
}
} while (!done);
DCHECK_EQ(state_.LoadRelaxed(), -1);
#else
CHECK_MUTEX_CALL(pthread_rwlock_wrlock, (&rwlock_));
#endif
DCHECK_EQ(exclusive_owner_, 0U);
exclusive_owner_ = SafeGetTid(self);
RegisterAsLocked(self);
AssertExclusiveHeld(self);
}
void ReaderWriterMutex::ExclusiveUnlock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
AssertExclusiveHeld(self);
RegisterAsUnlocked(self);
DCHECK_NE(exclusive_owner_, 0U);
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_.LoadRelaxed();
if (LIKELY(cur_state == -1)) {
// We're no longer the owner.
exclusive_owner_ = 0;
// Change state from -1 to 0 and impose load/store ordering appropriate for lock release.
// Note, the relaxed loads below musn't reorder before the CompareExchange.
// TODO: the ordering here is non-trivial as state is split across 3 fields, fix by placing
// a status bit into the state on contention.
done = state_.CompareExchangeWeakSequentiallyConsistent(-1 /* cur_state*/, 0 /* new state */);
if (LIKELY(done)) { // Weak CAS may fail spuriously.
// Wake any waiters.
if (UNLIKELY(num_pending_readers_.LoadRelaxed() > 0 ||
num_pending_writers_.LoadRelaxed() > 0)) {
futex(state_.Address(), FUTEX_WAKE, -1, NULL, NULL, 0);
}
}
} else {
LOG(FATAL) << "Unexpected state_:" << cur_state << " for " << name_;
}
} while (!done);
#else
exclusive_owner_ = 0;
CHECK_MUTEX_CALL(pthread_rwlock_unlock, (&rwlock_));
#endif
}
#if HAVE_TIMED_RWLOCK
bool ReaderWriterMutex::ExclusiveLockWithTimeout(Thread* self, int64_t ms, int32_t ns) {
DCHECK(self == NULL || self == Thread::Current());
#if ART_USE_FUTEXES
bool done = false;
timespec end_abs_ts;
InitTimeSpec(true, CLOCK_MONOTONIC, ms, ns, &end_abs_ts);
do {
int32_t cur_state = state_.LoadRelaxed();
if (cur_state == 0) {
// Change state from 0 to -1 and impose load/store ordering appropriate for lock acquisition.
done = state_.CompareExchangeWeakAcquire(0 /* cur_state */, -1 /* new state */);
} else {
// Failed to acquire, hang up.
timespec now_abs_ts;
InitTimeSpec(true, CLOCK_MONOTONIC, 0, 0, &now_abs_ts);
timespec rel_ts;
if (ComputeRelativeTimeSpec(&rel_ts, end_abs_ts, now_abs_ts)) {
return false; // Timed out.
}
ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
++num_pending_writers_;
if (futex(state_.Address(), FUTEX_WAIT, cur_state, &rel_ts, NULL, 0) != 0) {
if (errno == ETIMEDOUT) {
--num_pending_writers_;
return false; // Timed out.
} else if ((errno != EAGAIN) && (errno != EINTR)) {
// EAGAIN and EINTR both indicate a spurious failure,
// recompute the relative time out from now and try again.
// We don't use TEMP_FAILURE_RETRY so we can recompute rel_ts;
PLOG(FATAL) << "timed futex wait failed for " << name_;
}
}
--num_pending_writers_;
}
} while (!done);
#else
timespec ts;
InitTimeSpec(true, CLOCK_REALTIME, ms, ns, &ts);
int result = pthread_rwlock_timedwrlock(&rwlock_, &ts);
if (result == ETIMEDOUT) {
return false;
}
if (result != 0) {
errno = result;
PLOG(FATAL) << "pthread_rwlock_timedwrlock failed for " << name_;
}
#endif
exclusive_owner_ = SafeGetTid(self);
RegisterAsLocked(self);
AssertSharedHeld(self);
return true;
}
#endif
bool ReaderWriterMutex::SharedTryLock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_.LoadRelaxed();
if (cur_state >= 0) {
// Add as an extra reader and impose load/store ordering appropriate for lock acquisition.
done = state_.CompareExchangeWeakAcquire(cur_state, cur_state + 1);
} else {
// Owner holds it exclusively.
return false;
}
} while (!done);
#else
int result = pthread_rwlock_tryrdlock(&rwlock_);
if (result == EBUSY) {
return false;
}
if (result != 0) {
errno = result;
PLOG(FATAL) << "pthread_mutex_trylock failed for " << name_;
}
#endif
RegisterAsLocked(self);
AssertSharedHeld(self);
return true;
}
bool ReaderWriterMutex::IsSharedHeld(const Thread* self) const {
DCHECK(self == NULL || self == Thread::Current());
bool result;
if (UNLIKELY(self == NULL)) { // Handle unattached threads.
result = IsExclusiveHeld(self); // TODO: a better best effort here.
} else {
result = (self->GetHeldMutex(level_) == this);
}
return result;
}
void ReaderWriterMutex::Dump(std::ostream& os) const {
os << name_
<< " level=" << static_cast<int>(level_)
<< " owner=" << GetExclusiveOwnerTid()
#if ART_USE_FUTEXES
<< " state=" << state_.LoadSequentiallyConsistent()
<< " num_pending_writers=" << num_pending_writers_.LoadSequentiallyConsistent()
<< " num_pending_readers=" << num_pending_readers_.LoadSequentiallyConsistent()
#endif
<< " ";
DumpContention(os);
}
std::ostream& operator<<(std::ostream& os, const ReaderWriterMutex& mu) {
mu.Dump(os);
return os;
}
ConditionVariable::ConditionVariable(const char* name, Mutex& guard)
: name_(name), guard_(guard) {
#if ART_USE_FUTEXES
DCHECK_EQ(0, sequence_.LoadRelaxed());
num_waiters_ = 0;
#else
pthread_condattr_t cond_attrs;
CHECK_MUTEX_CALL(pthread_condattr_init, (&cond_attrs));
#if !defined(__APPLE__)
// Apple doesn't have CLOCK_MONOTONIC or pthread_condattr_setclock.
CHECK_MUTEX_CALL(pthread_condattr_setclock(&cond_attrs, CLOCK_MONOTONIC));
#endif
CHECK_MUTEX_CALL(pthread_cond_init, (&cond_, &cond_attrs));
#endif
}
ConditionVariable::~ConditionVariable() {
#if ART_USE_FUTEXES
if (num_waiters_!= 0) {
Runtime* runtime = Runtime::Current();
bool shutting_down = runtime == nullptr || runtime->IsShuttingDown(Thread::Current());
LOG(shutting_down ? WARNING : FATAL) << "ConditionVariable::~ConditionVariable for " << name_
<< " called with " << num_waiters_ << " waiters.";
}
#else
// We can't use CHECK_MUTEX_CALL here because on shutdown a suspended daemon thread
// may still be using condition variables.
int rc = pthread_cond_destroy(&cond_);
if (rc != 0) {
errno = rc;
MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
Runtime* runtime = Runtime::Current();
bool shutting_down = (runtime == NULL) || runtime->IsShuttingDownLocked();
PLOG(shutting_down ? WARNING : FATAL) << "pthread_cond_destroy failed for " << name_;
}
#endif
}
void ConditionVariable::Broadcast(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
// TODO: enable below, there's a race in thread creation that causes false failures currently.
// guard_.AssertExclusiveHeld(self);
DCHECK_EQ(guard_.GetExclusiveOwnerTid(), SafeGetTid(self));
#if ART_USE_FUTEXES
if (num_waiters_ > 0) {
sequence_++; // Indicate the broadcast occurred.
bool done = false;
do {
int32_t cur_sequence = sequence_.LoadRelaxed();
// Requeue waiters onto mutex. The waiter holds the contender count on the mutex high ensuring
// mutex unlocks will awaken the requeued waiter thread.
done = futex(sequence_.Address(), FUTEX_CMP_REQUEUE, 0,
reinterpret_cast<const timespec*>(std::numeric_limits<int32_t>::max()),
guard_.state_.Address(), cur_sequence) != -1;
if (!done) {
if (errno != EAGAIN) {
PLOG(FATAL) << "futex cmp requeue failed for " << name_;
}
}
} while (!done);
}
#else
CHECK_MUTEX_CALL(pthread_cond_broadcast, (&cond_));
#endif
}
void ConditionVariable::Signal(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
guard_.AssertExclusiveHeld(self);
#if ART_USE_FUTEXES
if (num_waiters_ > 0) {
sequence_++; // Indicate a signal occurred.
// Futex wake 1 waiter who will then come and in contend on mutex. It'd be nice to requeue them
// to avoid this, however, requeueing can only move all waiters.
int num_woken = futex(sequence_.Address(), FUTEX_WAKE, 1, NULL, NULL, 0);
// Check something was woken or else we changed sequence_ before they had chance to wait.
CHECK((num_woken == 0) || (num_woken == 1));
}
#else
CHECK_MUTEX_CALL(pthread_cond_signal, (&cond_));
#endif
}
void ConditionVariable::Wait(Thread* self) {
guard_.CheckSafeToWait(self);
WaitHoldingLocks(self);
}
void ConditionVariable::WaitHoldingLocks(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
guard_.AssertExclusiveHeld(self);
unsigned int old_recursion_count = guard_.recursion_count_;
#if ART_USE_FUTEXES
num_waiters_++;
// Ensure the Mutex is contended so that requeued threads are awoken.
guard_.num_contenders_++;
guard_.recursion_count_ = 1;
int32_t cur_sequence = sequence_.LoadRelaxed();
guard_.ExclusiveUnlock(self);
if (futex(sequence_.Address(), FUTEX_WAIT, cur_sequence, NULL, NULL, 0) != 0) {
// Futex failed, check it is an expected error.
// EAGAIN == EWOULDBLK, so we let the caller try again.
// EINTR implies a signal was sent to this thread.
if ((errno != EINTR) && (errno != EAGAIN)) {
PLOG(FATAL) << "futex wait failed for " << name_;
}
}
guard_.ExclusiveLock(self);
CHECK_GE(num_waiters_, 0);
num_waiters_--;
// We awoke and so no longer require awakes from the guard_'s unlock.
CHECK_GE(guard_.num_contenders_.LoadRelaxed(), 0);
guard_.num_contenders_--;
#else
uint64_t old_owner = guard_.exclusive_owner_;
guard_.exclusive_owner_ = 0;
guard_.recursion_count_ = 0;
CHECK_MUTEX_CALL(pthread_cond_wait, (&cond_, &guard_.mutex_));
guard_.exclusive_owner_ = old_owner;
#endif
guard_.recursion_count_ = old_recursion_count;
}
void ConditionVariable::TimedWait(Thread* self, int64_t ms, int32_t ns) {
DCHECK(self == NULL || self == Thread::Current());
guard_.AssertExclusiveHeld(self);
guard_.CheckSafeToWait(self);
unsigned int old_recursion_count = guard_.recursion_count_;
#if ART_USE_FUTEXES
timespec rel_ts;
InitTimeSpec(false, CLOCK_REALTIME, ms, ns, &rel_ts);
num_waiters_++;
// Ensure the Mutex is contended so that requeued threads are awoken.
guard_.num_contenders_++;
guard_.recursion_count_ = 1;
int32_t cur_sequence = sequence_.LoadRelaxed();
guard_.ExclusiveUnlock(self);
if (futex(sequence_.Address(), FUTEX_WAIT, cur_sequence, &rel_ts, NULL, 0) != 0) {
if (errno == ETIMEDOUT) {
// Timed out we're done.
} else if ((errno == EAGAIN) || (errno == EINTR)) {
// A signal or ConditionVariable::Signal/Broadcast has come in.
} else {
PLOG(FATAL) << "timed futex wait failed for " << name_;
}
}
guard_.ExclusiveLock(self);
CHECK_GE(num_waiters_, 0);
num_waiters_--;
// We awoke and so no longer require awakes from the guard_'s unlock.
CHECK_GE(guard_.num_contenders_.LoadRelaxed(), 0);
guard_.num_contenders_--;
#else
#if !defined(__APPLE__)
int clock = CLOCK_MONOTONIC;
#else
int clock = CLOCK_REALTIME;
#endif
uint64_t old_owner = guard_.exclusive_owner_;
guard_.exclusive_owner_ = 0;
guard_.recursion_count_ = 0;
timespec ts;
InitTimeSpec(true, clock, ms, ns, &ts);
int rc = TEMP_FAILURE_RETRY(pthread_cond_timedwait(&cond_, &guard_.mutex_, &ts));
if (rc != 0 && rc != ETIMEDOUT) {
errno = rc;
PLOG(FATAL) << "TimedWait failed for " << name_;
}
guard_.exclusive_owner_ = old_owner;
#endif
guard_.recursion_count_ = old_recursion_count;
}
void Locks::Init() {
if (logging_lock_ != nullptr) {
// Already initialized.
if (kRuntimeISA == kX86 || kRuntimeISA == kX86_64) {
DCHECK(modify_ldt_lock_ != nullptr);
} else {
DCHECK(modify_ldt_lock_ == nullptr);
}
DCHECK(abort_lock_ != nullptr);
DCHECK(alloc_tracker_lock_ != nullptr);
DCHECK(allocated_monitor_ids_lock_ != nullptr);
DCHECK(allocated_thread_ids_lock_ != nullptr);
DCHECK(breakpoint_lock_ != nullptr);
DCHECK(classlinker_classes_lock_ != nullptr);
DCHECK(deoptimization_lock_ != nullptr);
DCHECK(heap_bitmap_lock_ != nullptr);
DCHECK(intern_table_lock_ != nullptr);
DCHECK(logging_lock_ != nullptr);
DCHECK(mutator_lock_ != nullptr);
DCHECK(profiler_lock_ != nullptr);
DCHECK(thread_list_lock_ != nullptr);
DCHECK(thread_list_suspend_thread_lock_ != nullptr);
DCHECK(thread_suspend_count_lock_ != nullptr);
DCHECK(trace_lock_ != nullptr);
DCHECK(unexpected_signal_lock_ != nullptr);
} else {
// Create global locks in level order from highest lock level to lowest.
LockLevel current_lock_level = kThreadListSuspendThreadLock;
DCHECK(thread_list_suspend_thread_lock_ == nullptr);
thread_list_suspend_thread_lock_ =
new Mutex("thread list suspend thread by .. lock", current_lock_level);
#define UPDATE_CURRENT_LOCK_LEVEL(new_level) \
if (new_level >= current_lock_level) { \
/* Do not use CHECKs or FATAL here, abort_lock_ is not setup yet. */ \
fprintf(stderr, "New local level %d is not less than current level %d\n", \
new_level, current_lock_level); \
exit(1); \
} \
current_lock_level = new_level;
UPDATE_CURRENT_LOCK_LEVEL(kInstrumentEntrypointsLock);
DCHECK(instrument_entrypoints_lock_ == nullptr);
instrument_entrypoints_lock_ = new Mutex("instrument entrypoint lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kMutatorLock);
DCHECK(mutator_lock_ == nullptr);
mutator_lock_ = new ReaderWriterMutex("mutator lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kHeapBitmapLock);
DCHECK(heap_bitmap_lock_ == nullptr);
heap_bitmap_lock_ = new ReaderWriterMutex("heap bitmap lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kTraceLock);
DCHECK(trace_lock_ == nullptr);
trace_lock_ = new Mutex("trace lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kRuntimeShutdownLock);
DCHECK(runtime_shutdown_lock_ == nullptr);
runtime_shutdown_lock_ = new Mutex("runtime shutdown lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kProfilerLock);
DCHECK(profiler_lock_ == nullptr);
profiler_lock_ = new Mutex("profiler lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kDeoptimizationLock);
DCHECK(deoptimization_lock_ == nullptr);
deoptimization_lock_ = new Mutex("Deoptimization lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kAllocTrackerLock);
DCHECK(alloc_tracker_lock_ == nullptr);
alloc_tracker_lock_ = new Mutex("AllocTracker lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kThreadListLock);
DCHECK(thread_list_lock_ == nullptr);
thread_list_lock_ = new Mutex("thread list lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kBreakpointLock);
DCHECK(breakpoint_lock_ == nullptr);
breakpoint_lock_ = new ReaderWriterMutex("breakpoint lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kClassLinkerClassesLock);
DCHECK(classlinker_classes_lock_ == nullptr);
classlinker_classes_lock_ = new ReaderWriterMutex("ClassLinker classes lock",
current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kMonitorPoolLock);
DCHECK(allocated_monitor_ids_lock_ == nullptr);
allocated_monitor_ids_lock_ = new Mutex("allocated monitor ids lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kAllocatedThreadIdsLock);
DCHECK(allocated_thread_ids_lock_ == nullptr);
allocated_thread_ids_lock_ = new Mutex("allocated thread ids lock", current_lock_level);
if (kRuntimeISA == kX86 || kRuntimeISA == kX86_64) {
UPDATE_CURRENT_LOCK_LEVEL(kModifyLdtLock);
DCHECK(modify_ldt_lock_ == nullptr);
modify_ldt_lock_ = new Mutex("modify_ldt lock", current_lock_level);
}
UPDATE_CURRENT_LOCK_LEVEL(kInternTableLock);
DCHECK(intern_table_lock_ == nullptr);
intern_table_lock_ = new Mutex("InternTable lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kReferenceProcessorLock);
DCHECK(reference_processor_lock_ == nullptr);
reference_processor_lock_ = new Mutex("ReferenceProcessor lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueClearedReferencesLock);
DCHECK(reference_queue_cleared_references_lock_ == nullptr);
reference_queue_cleared_references_lock_ = new Mutex("ReferenceQueue cleared references lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueWeakReferencesLock);
DCHECK(reference_queue_weak_references_lock_ == nullptr);
reference_queue_weak_references_lock_ = new Mutex("ReferenceQueue cleared references lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueFinalizerReferencesLock);
DCHECK(reference_queue_finalizer_references_lock_ == nullptr);
reference_queue_finalizer_references_lock_ = new Mutex("ReferenceQueue finalizer references lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueuePhantomReferencesLock);
DCHECK(reference_queue_phantom_references_lock_ == nullptr);
reference_queue_phantom_references_lock_ = new Mutex("ReferenceQueue phantom references lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kReferenceQueueSoftReferencesLock);
DCHECK(reference_queue_soft_references_lock_ == nullptr);
reference_queue_soft_references_lock_ = new Mutex("ReferenceQueue soft references lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kAbortLock);
DCHECK(abort_lock_ == nullptr);
abort_lock_ = new Mutex("abort lock", current_lock_level, true);
UPDATE_CURRENT_LOCK_LEVEL(kThreadSuspendCountLock);
DCHECK(thread_suspend_count_lock_ == nullptr);
thread_suspend_count_lock_ = new Mutex("thread suspend count lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kUnexpectedSignalLock);
DCHECK(unexpected_signal_lock_ == nullptr);
unexpected_signal_lock_ = new Mutex("unexpected signal lock", current_lock_level, true);
UPDATE_CURRENT_LOCK_LEVEL(kMemMapsLock);
DCHECK(mem_maps_lock_ == nullptr);
mem_maps_lock_ = new Mutex("mem maps lock", current_lock_level);
UPDATE_CURRENT_LOCK_LEVEL(kLoggingLock);
DCHECK(logging_lock_ == nullptr);
logging_lock_ = new Mutex("logging lock", current_lock_level, true);
#undef UPDATE_CURRENT_LOCK_LEVEL
}
}
} // namespace art