blob: a4347ba6d21130af1974beecf439c4e7fb1df065 [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 "cutils/atomic.h"
#include "cutils/atomic-inline.h"
#include "logging.h"
#include "runtime.h"
#include "scoped_thread_state_change.h"
#include "thread.h"
#include "utils.h"
#if defined(__APPLE__)
#include "AvailabilityMacros.h" // For MAC_OS_X_VERSION_MAX_ALLOWED
// No clocks to specify on OS/X, fake value to pass to routines that require a clock.
#define CLOCK_REALTIME 0xebadf00d
#endif
#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());
}
}
// Initialize a timespec to either an absolute or relative time.
static void InitTimeSpec(Thread* self, bool absolute, int clock, int64_t ms, int32_t ns,
timespec* ts) {
int64_t endSec;
if (absolute) {
#if !defined(__APPLE__)
clock_gettime(clock, ts);
#else
UNUSED(clock);
timeval tv;
gettimeofday(&tv, NULL);
ts->tv_sec = tv.tv_sec;
ts->tv_nsec = tv.tv_usec * 1000;
#endif
} else {
ts->tv_sec = 0;
ts->tv_nsec = 0;
}
endSec = ts->tv_sec + ms / 1000;
if (UNLIKELY(endSec >= 0x7fffffff)) {
std::ostringstream ss;
ScopedObjectAccess soa(self);
self->Dump(ss);
LOG(INFO) << "Note: end time exceeds epoch: " << ss.str();
endSec = 0x7ffffffe;
}
ts->tv_sec = endSec;
ts->tv_nsec = (ts->tv_nsec + (ms % 1000) * 1000000) + ns;
// Catch rollover.
if (ts->tv_nsec >= 1000000000L) {
ts->tv_sec++;
ts->tv_nsec -= 1000000000L;
}
}
#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
BaseMutex::BaseMutex(const char* name, LockLevel level) : level_(level), name_(name) {}
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) {
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);
}
}
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.
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) {
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
}
std::string Mutex::Dump() const {
return StringPrintf("%s %s level=%d count=%d owner=%llx",
recursive_ ? "recursive" : "non-recursive",
name_.c_str(),
static_cast<int>(level_),
recursion_count_,
GetExclusiveOwnerTid());
}
std::ostream& operator<<(std::ostream& os, const Mutex& mu) {
return os << mu.Dump();
}
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.
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(self, 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(self, 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.
}
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(self, 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.
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
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
}
std::string ReaderWriterMutex::Dump() const {
return StringPrintf("%s level=%d owner=%llx",
name_.c_str(),
static_cast<int>(level_),
GetExclusiveOwnerTid());
}
std::ostream& operator<<(std::ostream& os, const ReaderWriterMutex& mu) {
return os << mu.Dump();
}
ConditionVariable::ConditionVariable(const std::string& name, Mutex& guard)
: name_(name), guard_(guard) {
#if ART_USE_FUTEXES
state_ = 0;
num_waiters_ = 0;
num_awoken_ = 0;
#else
CHECK_MUTEX_CALL(pthread_cond_init, (&cond_, NULL));
#endif
}
ConditionVariable::~ConditionVariable() {
#if !ART_USE_FUTEXES
// 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);
#if ART_USE_FUTEXES
if (num_waiters_ > 0) {
android_atomic_inc(&state_); // Indicate a wake has occurred to waiters coming in.
bool done = false;
do {
int32_t cur_state = state_;
// Compute number of waiters requeued and add to mutex contenders.
int32_t num_requeued = num_waiters_ - num_awoken_;
android_atomic_add(num_requeued, &guard_.num_contenders_);
// Requeue waiters onto contenders.
done = futex(&state_, FUTEX_CMP_REQUEUE, 0,
reinterpret_cast<const timespec*>(std::numeric_limits<int32_t>::max()),
&guard_.state_, cur_state) != -1;
if (!done) {
if (errno != EAGAIN) {
PLOG(FATAL) << "futex cmp requeue failed for " << name_;
}
} else {
num_awoken_ = num_waiters_;
}
} 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(&state_); // Indicate a wake has occurred to waiters coming in.
// 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.
if (futex(&state_, FUTEX_WAKE, 1, NULL, NULL, 0) == 1) {
// Wake success.
// We weren't requeued, however, to make accounting simpler in the Wait code, increment the
// number of contenders on the mutex.
num_awoken_++;
android_atomic_inc(&guard_.num_contenders_);
}
}
#else
CHECK_MUTEX_CALL(pthread_cond_signal, (&cond_));
#endif
}
void ConditionVariable::Wait(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
guard_.AssertExclusiveHeld(self);
guard_.CheckSafeToWait(self);
unsigned int old_recursion_count = guard_.recursion_count_;
#if ART_USE_FUTEXES
int32_t cur_state = state_;
num_waiters_++;
guard_.recursion_count_ = 1;
guard_.ExclusiveUnlock(self);
bool woken = true;
while (futex(&state_, FUTEX_WAIT, cur_state, NULL, NULL, 0) != 0) {
if (errno == EINTR || errno == EAGAIN) {
if (state_ != cur_state) {
// We failed and a signal has come in.
woken = false;
break;
}
} else {
PLOG(FATAL) << "futex wait failed for " << name_;
}
}
guard_.ExclusiveLock(self);
num_waiters_--;
if (woken) {
// If we were woken we were requeued on the mutex, decrement the mutex's contender count.
android_atomic_dec(&guard_.num_contenders_);
num_awoken_--;
}
#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);
guard_.CheckSafeToWait(self);
unsigned int old_recursion_count = guard_.recursion_count_;
#if ART_USE_FUTEXES
// Record the original end time so that if the futex call fails we can recompute the appropriate
// relative time.
timespec end_abs_ts;
InitTimeSpec(self, true, CLOCK_REALTIME, ms, ns, &end_abs_ts);
timespec rel_ts;
InitTimeSpec(self, false, CLOCK_REALTIME, ms, ns, &rel_ts);
// Read state so that we can know if a signal comes in during before we sleep.
int32_t cur_state = state_;
num_waiters_++;
guard_.recursion_count_ = 1;
guard_.ExclusiveUnlock(self);
bool woken = true; // Did the futex wait end because we were awoken?
while (futex(&state_, FUTEX_WAIT, cur_state, &rel_ts, NULL, 0) != 0) {
if (errno == ETIMEDOUT) {
woken = false;
break;
}
if ((errno == EINTR) || (errno == EAGAIN)) {
if (state_ != cur_state) {
// We failed and a signal has come in.
woken = false;
break;
}
timespec now_abs_ts;
InitTimeSpec(self, true, CLOCK_REALTIME, 0, 0, &now_abs_ts);
if (ComputeRelativeTimeSpec(&rel_ts, end_abs_ts, now_abs_ts)) {
// futex failed and we timed out in the meantime.
woken = false;
break;
}
} else {
PLOG(FATAL) << "timed futex wait failed for " << name_;
}
}
guard_.ExclusiveLock(self);
num_waiters_--;
if (woken) {
// If we were woken we were requeued on the mutex, decrement the mutex's contender count.
android_atomic_dec(&guard_.num_contenders_);
num_awoken_--;
}
#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(self, true, clock, ms, ns, &ts);
int rc = 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