blob: e2ab51f2f90f3241488eaf086c4afef4b11d1fd0 [file] [log] [blame]
/*
* 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 "base/logging.h"
#include "cutils/atomic.h"
#include "cutils/atomic-inline.h"
#include "runtime.h"
#include "scoped_thread_state_change.h"
#include "thread.h"
#include "utils.h"
#define CHECK_MUTEX_CALL(call, args) CHECK_PTHREAD_CALL(call, args, name_)
extern int pthread_mutex_lock(pthread_mutex_t* mutex) EXCLUSIVE_LOCK_FUNCTION(mutex);
extern int pthread_mutex_unlock(pthread_mutex_t* mutex) UNLOCK_FUNCTION(1);
extern int pthread_mutex_trylock(pthread_mutex_t* mutex) EXCLUSIVE_TRYLOCK_FUNCTION(0, mutex);
#if ART_USE_FUTEXES
#include "linux/futex.h"
#include "sys/syscall.h"
#ifndef SYS_futex
#define SYS_futex __NR_futex
#endif
int futex(volatile int *uaddr, int op, int val, const struct timespec *timeout, volatile int *uaddr2, int val3) {
return syscall(SYS_futex, uaddr, op, val, timeout, uaddr2, val3);
}
#endif // ART_USE_FUTEXES
namespace art {
// This works on Mac OS 10.6 but hasn't been tested on older releases.
struct __attribute__((__may_alias__)) darwin_pthread_mutex_t {
long padding0;
int padding1;
uint32_t padding2;
int16_t padding3;
int16_t padding4;
uint32_t padding5;
pthread_t darwin_pthread_mutex_owner;
// ...other stuff we don't care about.
};
struct __attribute__((__may_alias__)) darwin_pthread_rwlock_t {
long padding0;
pthread_mutex_t padding1;
int padding2;
pthread_cond_t padding3;
pthread_cond_t padding4;
int padding5;
int padding6;
pthread_t darwin_pthread_rwlock_owner;
// ...other stuff we don't care about.
};
struct __attribute__((__may_alias__)) glibc_pthread_mutex_t {
int32_t padding0[2];
int owner;
// ...other stuff we don't care about.
};
struct __attribute__((__may_alias__)) glibc_pthread_rwlock_t {
#ifdef __LP64__
int32_t padding0[6];
#else
int32_t padding0[7];
#endif
int writer;
// ...other stuff we don't care about.
};
static uint64_t SafeGetTid(const Thread* self) {
if (self != NULL) {
return static_cast<uint64_t>(self->GetTid());
} else {
return static_cast<uint64_t>(GetTid());
}
}
#if ART_USE_FUTEXES
static bool ComputeRelativeTimeSpec(timespec* result_ts, const timespec& lhs, const timespec& rhs) {
const long int 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
#if CONTENTION_LOGGING
// A guard for all_mutexes_ that's not a mutex (Mutexes must CAS to acquire and busy wait).
static AtomicInteger all_mutexes_guard_;
// All created mutexes guarded by all_mutexes_guard_.
std::set<BaseMutex*>* all_mutexes_;
class ScopedAllMutexesLock {
public:
ScopedAllMutexesLock(const BaseMutex* mutex) : mutex_(mutex) {
while (!all_mutexes_guard_.CompareAndSwap(0, reinterpret_cast<int32_t>(mutex))) {
NanoSleep(100);
}
}
~ScopedAllMutexesLock() {
while (!all_mutexes_guard_.CompareAndSwap(reinterpret_cast<int32_t>(mutex_), 0)) {
NanoSleep(100);
}
}
private:
const BaseMutex* const mutex_;
};
#endif
BaseMutex::BaseMutex(const char* name, LockLevel level) : level_(level), name_(name) {
#if CONTENTION_LOGGING
ScopedAllMutexesLock mu(this);
if (all_mutexes_ == NULL) {
// We leak the global set of all mutexes to avoid ordering issues in global variable
// construction/destruction.
all_mutexes_ = new std::set<BaseMutex*>();
}
all_mutexes_->insert(this);
#endif
}
BaseMutex::~BaseMutex() {
#if CONTENTION_LOGGING
ScopedAllMutexesLock mu(this);
all_mutexes_->erase(this);
#endif
}
void BaseMutex::DumpAll(std::ostream& os) {
#if CONTENTION_LOGGING
os << "Mutex logging:\n";
ScopedAllMutexesLock mu(reinterpret_cast<const BaseMutex*>(-1));
typedef std::set<BaseMutex*>::const_iterator It;
for (It it = all_mutexes_->begin(); it != all_mutexes_->end(); ++it) {
BaseMutex* mutex = *it;
mutex->Dump(os);
os << "\n";
}
#endif
}
static void CheckUnattachedThread(LockLevel level) NO_THREAD_SAFETY_ANALYSIS {
// The check below enumerates the cases where we expect not to be able to sanity check locks
// on a thread. Lock checking is disabled to avoid deadlock when checking shutdown lock.
// TODO: tighten this check.
if (kDebugLocking) {
Runtime* runtime = Runtime::Current();
CHECK(runtime == NULL || !runtime->IsStarted() || runtime->IsShuttingDown() ||
level == kDefaultMutexLevel || level == kRuntimeShutdownLock ||
level == kThreadListLock || level == kLoggingLock || level == kAbortLock);
}
}
void BaseMutex::RegisterAsLocked(Thread* self) {
if (UNLIKELY(self == NULL)) {
CheckUnattachedThread(level_);
return;
}
if (kDebugLocking) {
// Check if a bad Mutex of this level or lower is held.
bool bad_mutexes_held = false;
for (int i = level_; i >= 0; --i) {
BaseMutex* held_mutex = self->GetHeldMutex(static_cast<LockLevel>(i));
if (UNLIKELY(held_mutex != NULL)) {
LOG(ERROR) << "Lock level violation: holding \"" << held_mutex->name_ << "\" (level " << i
<< ") while locking \"" << name_ << "\" (level " << static_cast<int>(level_) << ")";
if (i > kAbortLock) {
// Only abort in the check below if this is more than abort level lock.
bad_mutexes_held = true;
}
}
}
CHECK(!bad_mutexes_held);
}
// Don't record monitors as they are outside the scope of analysis. They may be inspected off of
// the monitor list.
if (level_ != kMonitorLock) {
self->SetHeldMutex(level_, this);
}
}
void BaseMutex::RegisterAsUnlocked(Thread* self) {
if (UNLIKELY(self == NULL)) {
CheckUnattachedThread(level_);
return;
}
if (level_ != kMonitorLock) {
if (kDebugLocking && !gAborting) {
CHECK(self->GetHeldMutex(level_) == this) << "Unlocking on unacquired mutex: " << name_;
}
self->SetHeldMutex(level_, NULL);
}
}
void BaseMutex::CheckSafeToWait(Thread* self) {
if (self == NULL) {
CheckUnattachedThread(level_);
return;
}
if (kDebugLocking) {
CHECK(self->GetHeldMutex(level_) == this) << "Waiting on unacquired mutex: " << name_;
bool bad_mutexes_held = false;
for (int i = kMaxMutexLevel; i >= 0; --i) {
if (i != level_) {
BaseMutex* held_mutex = self->GetHeldMutex(static_cast<LockLevel>(i));
if (held_mutex != NULL) {
LOG(ERROR) << "Holding " << held_mutex->name_ << " (level " << i
<< ") while performing wait on: "
<< name_ << " (level " << static_cast<int>(level_) << ")";
bad_mutexes_held = true;
}
}
}
CHECK(!bad_mutexes_held);
}
}
void BaseMutex::RecordContention(uint64_t blocked_tid, uint64_t owner_tid, uint64_t milli_time_blocked) {
#if CONTENTION_LOGGING
++contention_count_;
wait_time_ += static_cast<uint32_t>(milli_time_blocked); // May overflow.
// This code is intentionally racy as it is only used for diagnostics.
uint32_t slot = cur_content_log_entry_;
if (contention_log_[slot].blocked_tid == blocked_tid &&
contention_log_[slot].owner_tid == blocked_tid) {
++contention_log_[slot].count;
} else {
uint32_t new_slot;
do {
slot = cur_content_log_entry_;
new_slot = (slot + 1) % kContentionLogSize;
} while(!cur_content_log_entry_.CompareAndSwap(slot, new_slot));
contention_log_[new_slot].blocked_tid = blocked_tid;
contention_log_[new_slot].owner_tid = owner_tid;
contention_log_[new_slot].count = 1;
}
#endif
}
class ScopedContentionRecorder {
public:
ScopedContentionRecorder(BaseMutex* mutex, uint64_t blocked_tid, uint64_t owner_tid) :
mutex_(mutex), blocked_tid_(blocked_tid), owner_tid_(owner_tid),
start_milli_time_(MilliTime()) {
}
~ScopedContentionRecorder() {
uint64_t end_milli_time = MilliTime();
mutex_->RecordContention(blocked_tid_, owner_tid_, end_milli_time - start_milli_time_);
}
private:
BaseMutex* const mutex_;
uint64_t blocked_tid_;
uint64_t owner_tid_;
const uint64_t start_milli_time_;
};
void BaseMutex::DumpContention(std::ostream& os) const {
#if CONTENTION_LOGGING
uint32_t wait_time = wait_time_;
uint32_t contention_count = contention_count_;
if (contention_count == 0) {
os << "never contended";
} else {
os << "contended " << contention_count << " times, average wait of contender " << (wait_time / contention_count) << "ms";
SafeMap<uint64_t, size_t> most_common_blocker;
SafeMap<uint64_t, size_t> most_common_blocked;
typedef SafeMap<uint64_t, size_t>::const_iterator It;
for (size_t i = 0; i < kContentionLogSize; ++i) {
uint64_t blocked_tid = contention_log_[i].blocked_tid;
uint64_t owner_tid = contention_log_[i].owner_tid;
uint32_t count = contention_log_[i].count;
if (count > 0) {
It 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 (It it = most_common_blocked.begin(); it != most_common_blocked.end(); ++it) {
if (it->second > max_tid_count) {
max_tid = it->first;
max_tid_count = it->second;
}
}
if (max_tid != 0) {
os << " sample shows most blocked tid=" << max_tid;
}
max_tid = 0;
max_tid_count = 0;
for (It it = most_common_blocker.begin(); it != most_common_blocker.end(); ++it) {
if (it->second > max_tid_count) {
max_tid = it->first;
max_tid_count = it->second;
}
}
if (max_tid != 0) {
os << " sample shows tid=" << max_tid << " owning during this time";
}
}
#endif
}
Mutex::Mutex(const char* name, LockLevel level, bool recursive)
: BaseMutex(name, level), recursive_(recursive), recursion_count_(0) {
#if ART_USE_FUTEXES
state_ = 0;
exclusive_owner_ = 0;
num_contenders_ = 0;
#elif defined(__BIONIC__) || defined(__APPLE__)
// Use recursive mutexes for bionic and Apple otherwise the
// non-recursive mutexes don't have TIDs to check lock ownership of.
pthread_mutexattr_t attributes;
CHECK_MUTEX_CALL(pthread_mutexattr_init, (&attributes));
CHECK_MUTEX_CALL(pthread_mutexattr_settype, (&attributes, PTHREAD_MUTEX_RECURSIVE));
CHECK_MUTEX_CALL(pthread_mutex_init, (&mutex_, &attributes));
CHECK_MUTEX_CALL(pthread_mutexattr_destroy, (&attributes));
#else
CHECK_MUTEX_CALL(pthread_mutex_init, (&mutex_, NULL));
#endif
}
Mutex::~Mutex() {
#if ART_USE_FUTEXES
if (state_ != 0) {
MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
Runtime* runtime = Runtime::Current();
bool shutting_down = (runtime == NULL) || runtime->IsShuttingDown();
LOG(shutting_down ? WARNING : FATAL) << "destroying mutex with owner: " << exclusive_owner_;
} else {
CHECK_EQ(exclusive_owner_, 0U) << "unexpectedly found an owner on unlocked mutex " << name_;
CHECK_EQ(num_contenders_, 0) << "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_);
Runtime* runtime = Runtime::Current();
bool shutting_down = (runtime == NULL) || runtime->IsShuttingDown();
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_;
if (cur_state == 0) {
// Change state from 0 to 1.
done = android_atomic_cmpxchg(0, 1, &state_) == 0;
} else {
// Failed to acquire, hang up.
ScopedContentionRecorder scr(this, GetExclusiveOwnerTid(), SafeGetTid(self));
android_atomic_inc(&num_contenders_);
if (futex(&state_, FUTEX_WAIT, 1, NULL, NULL, 0) != 0) {
if (errno != EAGAIN) {
PLOG(FATAL) << "futex wait failed for " << name_;
}
}
android_atomic_dec(&num_contenders_);
}
} while(!done);
DCHECK_EQ(state_, 1);
exclusive_owner_ = SafeGetTid(self);
#else
CHECK_MUTEX_CALL(pthread_mutex_lock, (&mutex_));
#endif
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_;
if (cur_state == 0) {
// Change state from 0 to 1.
done = android_atomic_cmpxchg(0, 1, &state_) == 0;
} else {
return false;
}
} while(!done);
DCHECK_EQ(state_, 1);
exclusive_owner_ = SafeGetTid(self);
#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
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);
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_;
if (cur_state == 1) {
// We're no longer the owner.
exclusive_owner_ = 0;
// Change state to 0.
done = android_atomic_cmpxchg(cur_state, 0, &state_) == 0;
if (done) { // Spurious fail?
// Wake a contender
if (num_contenders_ > 0) {
futex(&state_, FUTEX_WAKE, 1, NULL, NULL, 0);
}
}
} else {
LOG(FATAL) << "Unexpected state_:" << cur_state << " for " << name_;
}
} while(!done);
#else
CHECK_MUTEX_CALL(pthread_mutex_unlock, (&mutex_));
#endif
}
}
bool Mutex::IsExclusiveHeld(const Thread* self) const {
DCHECK(self == NULL || self == Thread::Current());
bool result = (GetExclusiveOwnerTid() == SafeGetTid(self));
if (kDebugLocking) {
// Sanity debug check that if we think it is locked we have it in our held mutexes.
if (result && self != NULL && level_ != kMonitorLock && !gAborting) {
CHECK_EQ(self->GetHeldMutex(level_), this);
}
}
return result;
}
uint64_t Mutex::GetExclusiveOwnerTid() const {
#if ART_USE_FUTEXES
return exclusive_owner_;
#elif defined(__BIONIC__)
return static_cast<uint64_t>((mutex_.value >> 16) & 0xffff);
#elif defined(__GLIBC__)
return reinterpret_cast<const glibc_pthread_mutex_t*>(&mutex_)->owner;
#elif defined(__APPLE__)
const darwin_pthread_mutex_t* dpmutex = reinterpret_cast<const darwin_pthread_mutex_t*>(&mutex_);
pthread_t owner = dpmutex->darwin_pthread_mutex_owner;
// 0 for unowned, -1 for PTHREAD_MTX_TID_SWITCHING
// TODO: should we make darwin_pthread_mutex_owner volatile and recheck until not -1?
if ((owner == (pthread_t)0) || (owner == (pthread_t)-1)) {
return 0;
}
uint64_t tid;
CHECK_PTHREAD_CALL(pthread_threadid_np, (owner, &tid), __FUNCTION__); // Requires Mac OS 10.6
return tid;
#else
#error unsupported C library
#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), exclusive_owner_(0), num_pending_readers_(0), num_pending_writers_(0)
#endif
{
#if !ART_USE_FUTEXES
CHECK_MUTEX_CALL(pthread_rwlock_init, (&rwlock_, NULL));
#endif
}
ReaderWriterMutex::~ReaderWriterMutex() {
#if ART_USE_FUTEXES
CHECK_EQ(state_, 0);
CHECK_EQ(exclusive_owner_, 0U);
CHECK_EQ(num_pending_readers_, 0);
CHECK_EQ(num_pending_writers_, 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->IsShuttingDown();
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_;
if (cur_state == 0) {
// Change state from 0 to -1.
done = android_atomic_cmpxchg(0, -1, &state_) == 0;
} else {
// Failed to acquire, hang up.
ScopedContentionRecorder scr(this, GetExclusiveOwnerTid(), SafeGetTid(self));
android_atomic_inc(&num_pending_writers_);
if (futex(&state_, FUTEX_WAIT, cur_state, NULL, NULL, 0) != 0) {
if (errno != EAGAIN) {
PLOG(FATAL) << "futex wait failed for " << name_;
}
}
android_atomic_dec(&num_pending_writers_);
}
} while(!done);
DCHECK_EQ(state_, -1);
exclusive_owner_ = SafeGetTid(self);
#else
CHECK_MUTEX_CALL(pthread_rwlock_wrlock, (&rwlock_));
#endif
RegisterAsLocked(self);
AssertExclusiveHeld(self);
}
void ReaderWriterMutex::ExclusiveUnlock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
AssertExclusiveHeld(self);
RegisterAsUnlocked(self);
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_;
if (cur_state == -1) {
// We're no longer the owner.
exclusive_owner_ = 0;
// Change state from -1 to 0.
done = android_atomic_cmpxchg(-1, 0, &state_) == 0;
if (done) { // cmpxchg may fail due to noise?
// Wake any waiters.
if (num_pending_readers_ > 0 || num_pending_writers_ > 0) {
futex(&state_, FUTEX_WAKE, -1, NULL, NULL, 0);
}
}
} else {
LOG(FATAL) << "Unexpected state_:" << cur_state << " for " << name_;
}
} while(!done);
#else
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_REALTIME, ms, ns, &end_abs_ts);
do {
int32_t cur_state = state_;
if (cur_state == 0) {
// Change state from 0 to -1.
done = android_atomic_cmpxchg(0, -1, &state_) == 0;
} else {
// Failed to acquire, hang up.
timespec now_abs_ts;
InitTimeSpec(true, CLOCK_REALTIME, 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, GetExclusiveOwnerTid(), SafeGetTid(self));
android_atomic_inc(&num_pending_writers_);
if (futex(&state_, FUTEX_WAIT, cur_state, &rel_ts, NULL, 0) != 0) {
if (errno == ETIMEDOUT) {
android_atomic_dec(&num_pending_writers_);
return false; // Timed out.
} else if (errno != EAGAIN && errno != EINTR) {
PLOG(FATAL) << "timed futex wait failed for " << name_;
}
}
android_atomic_dec(&num_pending_writers_);
}
} while(!done);
exclusive_owner_ = SafeGetTid(self);
#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
RegisterAsLocked(self);
AssertSharedHeld(self);
return true;
}
#endif
void ReaderWriterMutex::SharedLock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_;
if (cur_state >= 0) {
// Add as an extra reader.
done = android_atomic_cmpxchg(cur_state, cur_state + 1, &state_) == 0;
} else {
// Owner holds it exclusively, hang up.
ScopedContentionRecorder scr(this, GetExclusiveOwnerTid(), SafeGetTid(self));
android_atomic_inc(&num_pending_readers_);
if (futex(&state_, FUTEX_WAIT, cur_state, NULL, NULL, 0) != 0) {
if (errno != EAGAIN) {
PLOG(FATAL) << "futex wait failed for " << name_;
}
}
android_atomic_dec(&num_pending_readers_);
}
} while(!done);
#else
CHECK_MUTEX_CALL(pthread_rwlock_rdlock, (&rwlock_));
#endif
RegisterAsLocked(self);
AssertSharedHeld(self);
}
bool ReaderWriterMutex::SharedTryLock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_;
if (cur_state >= 0) {
// Add as an extra reader.
done = android_atomic_cmpxchg(cur_state, cur_state + 1, &state_) == 0;
} 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;
}
void ReaderWriterMutex::SharedUnlock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
AssertSharedHeld(self);
RegisterAsUnlocked(self);
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_;
if (LIKELY(cur_state > 0)) {
// Reduce state by 1.
done = android_atomic_cmpxchg(cur_state, cur_state - 1, &state_) == 0;
if (done && (cur_state - 1) == 0) { // cmpxchg may fail due to noise?
if (num_pending_writers_ > 0 || num_pending_readers_ > 0) {
// Wake any exclusive waiters as there are now no readers.
futex(&state_, FUTEX_WAKE, -1, NULL, NULL, 0);
}
}
} else {
LOG(FATAL) << "Unexpected state_:" << cur_state << " for " << name_;
}
} while(!done);
#else
CHECK_MUTEX_CALL(pthread_rwlock_unlock, (&rwlock_));
#endif
}
bool ReaderWriterMutex::IsExclusiveHeld(const Thread* self) const {
DCHECK(self == NULL || self == Thread::Current());
bool result = (GetExclusiveOwnerTid() == SafeGetTid(self));
if (kDebugLocking) {
// Sanity that if the pthread thinks we own the lock the Thread agrees.
if (self != NULL && result) {
CHECK_EQ(self->GetHeldMutex(level_), this);
}
}
return result;
}
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;
}
uint64_t ReaderWriterMutex::GetExclusiveOwnerTid() const {
#if ART_USE_FUTEXES
int32_t state = state_;
if (state == 0) {
return 0; // No owner.
} else if (state > 0) {
return -1; // Shared.
} else {
return exclusive_owner_;
}
#else
#if defined(__BIONIC__)
return rwlock_.writerThreadId;
#elif defined(__GLIBC__)
return reinterpret_cast<const glibc_pthread_rwlock_t*>(&rwlock_)->writer;
#elif defined(__APPLE__)
const darwin_pthread_rwlock_t*
dprwlock = reinterpret_cast<const darwin_pthread_rwlock_t*>(&rwlock_);
pthread_t owner = dprwlock->darwin_pthread_rwlock_owner;
if (owner == (pthread_t)0) {
return 0;
}
uint64_t tid;
CHECK_PTHREAD_CALL(pthread_threadid_np, (owner, &tid), __FUNCTION__); // Requires Mac OS 10.6
return tid;
#else
#error unsupported C library
#endif
#endif
}
void ReaderWriterMutex::Dump(std::ostream& os) const {
os << name_
<< " level=" << static_cast<int>(level_)
<< " owner=" << GetExclusiveOwnerTid() << " ";
DumpContention(os);
}
std::ostream& operator<<(std::ostream& os, const ReaderWriterMutex& mu) {
mu.Dump(os);
return os;
}
ConditionVariable::ConditionVariable(const std::string& name, Mutex& guard)
: name_(name), guard_(guard) {
#if ART_USE_FUTEXES
sequence_ = 0;
num_waiters_ = 0;
#else
CHECK_MUTEX_CALL(pthread_cond_init, (&cond_, NULL));
#endif
}
ConditionVariable::~ConditionVariable() {
#if ART_USE_FUTEXES
if (num_waiters_!= 0) {
MutexLock mu(Thread::Current(), *Locks::runtime_shutdown_lock_);
Runtime* runtime = Runtime::Current();
bool shutting_down = (runtime == NULL) || runtime->IsShuttingDown();
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->IsShuttingDown();
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) {
android_atomic_inc(&sequence_); // Indicate the broadcast occurred.
bool done = false;
do {
int32_t cur_sequence = sequence_;
// 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_, FUTEX_CMP_REQUEUE, 0,
reinterpret_cast<const timespec*>(std::numeric_limits<int32_t>::max()),
&guard_.state_, 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) {
android_atomic_inc(&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_, 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) {
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.
android_atomic_inc(&guard_.num_contenders_);
guard_.recursion_count_ = 1;
int32_t cur_sequence = sequence_;
guard_.ExclusiveUnlock(self);
if (futex(&sequence_, 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_, 0);
android_atomic_dec(&guard_.num_contenders_);
#else
guard_.recursion_count_ = 0;
CHECK_MUTEX_CALL(pthread_cond_wait, (&cond_, &guard_.mutex_));
#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);
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.
android_atomic_inc(&guard_.num_contenders_);
guard_.recursion_count_ = 1;
int32_t cur_sequence = sequence_;
guard_.ExclusiveUnlock(self);
if (futex(&sequence_, FUTEX_WAIT, cur_sequence, &rel_ts, NULL, 0) != 0) {
if (errno == ETIMEDOUT) {
// Timed out we're done.
} else if ((errno == EINTR) || (errno == EAGAIN)) {
// 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_, 0);
android_atomic_dec(&guard_.num_contenders_);
#else
#ifdef HAVE_TIMEDWAIT_MONOTONIC
#define TIMEDWAIT pthread_cond_timedwait_monotonic
int clock = CLOCK_MONOTONIC;
#else
#define TIMEDWAIT pthread_cond_timedwait
int clock = CLOCK_REALTIME;
#endif
guard_.recursion_count_ = 0;
timespec ts;
InitTimeSpec(true, clock, ms, ns, &ts);
int rc = TEMP_FAILURE_RETRY(TIMEDWAIT(&cond_, &guard_.mutex_, &ts));
if (rc != 0 && rc != ETIMEDOUT) {
errno = rc;
PLOG(FATAL) << "TimedWait failed for " << name_;
}
#endif
guard_.recursion_count_ = old_recursion_count;
}
} // namespace art