// Copyright 2017 The Abseil Authors.
//
// 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.
// Implementation of a small subset of Mutex and CondVar functionality
// for platforms where the production implementation hasn't been fully
// ported yet.
#include "absl/synchronization/mutex.h"
#if defined(_WIN32)
#include <chrono> // NOLINT(build/c++11)
#else
#include <sys/time.h>
#include <time.h>
#endif
#include <algorithm>
#include "absl/base/internal/raw_logging.h"
#include "absl/time/time.h"
namespace absl {
namespace synchronization_internal {
namespace {
// Return the current time plus the timeout.
absl::Time DeadlineFromTimeout(absl::Duration timeout) {
return absl::Now() + timeout;
}
// Limit the deadline to a positive, 32-bit time_t value to accommodate
// implementation restrictions. This also deals with InfinitePast and
// InfiniteFuture.
absl::Time LimitedDeadline(absl::Time deadline) {
deadline = std::max(absl::FromTimeT(0), deadline);
deadline = std::min(deadline, absl::FromTimeT(0x7fffffff));
return deadline;
}
} // namespace
#if defined(_WIN32)
MutexImpl::MutexImpl() {}
MutexImpl::~MutexImpl() {
if (locked_) {
std_mutex_.unlock();
}
}
void MutexImpl::Lock() {
std_mutex_.lock();
locked_ = true;
}
bool MutexImpl::TryLock() {
bool locked = std_mutex_.try_lock();
if (locked) locked_ = true;
return locked;
}
void MutexImpl::Unlock() {
locked_ = false;
released_.SignalAll();
std_mutex_.unlock();
}
CondVarImpl::CondVarImpl() {}
CondVarImpl::~CondVarImpl() {}
void CondVarImpl::Signal() { std_cv_.notify_one(); }
void CondVarImpl::SignalAll() { std_cv_.notify_all(); }
void CondVarImpl::Wait(MutexImpl* mu) {
mu->released_.SignalAll();
std_cv_.wait(mu->std_mutex_);
}
bool CondVarImpl::WaitWithDeadline(MutexImpl* mu, absl::Time deadline) {
mu->released_.SignalAll();
time_t when = ToTimeT(deadline);
int64_t nanos = ToInt64Nanoseconds(deadline - absl::FromTimeT(when));
std::chrono::system_clock::time_point deadline_tp =
std::chrono::system_clock::from_time_t(when) +
std::chrono::duration_cast<std::chrono::system_clock::duration>(
std::chrono::nanoseconds(nanos));
auto deadline_since_epoch =
std::chrono::duration_cast<std::chrono::duration<double>>(
deadline_tp - std::chrono::system_clock::from_time_t(0));
return std_cv_.wait_until(mu->std_mutex_, deadline_tp) ==
std::cv_status::timeout;
}
#else // ! _WIN32
MutexImpl::MutexImpl() {
ABSL_RAW_CHECK(pthread_mutex_init(&pthread_mutex_, nullptr) == 0,
"pthread error");
}
MutexImpl::~MutexImpl() {
if (locked_) {
ABSL_RAW_CHECK(pthread_mutex_unlock(&pthread_mutex_) == 0, "pthread error");
}
ABSL_RAW_CHECK(pthread_mutex_destroy(&pthread_mutex_) == 0, "pthread error");
}
void MutexImpl::Lock() {
ABSL_RAW_CHECK(pthread_mutex_lock(&pthread_mutex_) == 0, "pthread error");
locked_ = true;
}
bool MutexImpl::TryLock() {
bool locked = (0 == pthread_mutex_trylock(&pthread_mutex_));
if (locked) locked_ = true;
return locked;
}
void MutexImpl::Unlock() {
locked_ = false;
released_.SignalAll();
ABSL_RAW_CHECK(pthread_mutex_unlock(&pthread_mutex_) == 0, "pthread error");
}
CondVarImpl::CondVarImpl() {
ABSL_RAW_CHECK(pthread_cond_init(&pthread_cv_, nullptr) == 0,
"pthread error");
}
CondVarImpl::~CondVarImpl() {
ABSL_RAW_CHECK(pthread_cond_destroy(&pthread_cv_) == 0, "pthread error");
}
void CondVarImpl::Signal() {
ABSL_RAW_CHECK(pthread_cond_signal(&pthread_cv_) == 0, "pthread error");
}
void CondVarImpl::SignalAll() {
ABSL_RAW_CHECK(pthread_cond_broadcast(&pthread_cv_) == 0, "pthread error");
}
void CondVarImpl::Wait(MutexImpl* mu) {
mu->released_.SignalAll();
ABSL_RAW_CHECK(pthread_cond_wait(&pthread_cv_, &mu->pthread_mutex_) == 0,
"pthread error");
}
bool CondVarImpl::WaitWithDeadline(MutexImpl* mu, absl::Time deadline) {
mu->released_.SignalAll();
struct timespec ts = ToTimespec(deadline);
int rc = pthread_cond_timedwait(&pthread_cv_, &mu->pthread_mutex_, &ts);
if (rc == ETIMEDOUT) return true;
ABSL_RAW_CHECK(rc == 0, "pthread error");
return false;
}
#endif // ! _WIN32
void MutexImpl::Await(const Condition& cond) {
if (cond.Eval()) return;
released_.SignalAll();
do {
released_.Wait(this);
} while (!cond.Eval());
}
bool MutexImpl::AwaitWithDeadline(const Condition& cond, absl::Time deadline) {
if (cond.Eval()) return true;
released_.SignalAll();
while (true) {
if (released_.WaitWithDeadline(this, deadline)) return false;
if (cond.Eval()) return true;
}
}
} // namespace synchronization_internal
Mutex::Mutex() {}
Mutex::~Mutex() {}
void Mutex::Lock() { impl()->Lock(); }
void Mutex::Unlock() { impl()->Unlock(); }
bool Mutex::TryLock() { return impl()->TryLock(); }
void Mutex::ReaderLock() { Lock(); }
void Mutex::ReaderUnlock() { Unlock(); }
void Mutex::Await(const Condition& cond) { impl()->Await(cond); }
void Mutex::LockWhen(const Condition& cond) {
Lock();
Await(cond);
}
bool Mutex::AwaitWithDeadline(const Condition& cond, absl::Time deadline) {
return impl()->AwaitWithDeadline(
cond, synchronization_internal::LimitedDeadline(deadline));
}
bool Mutex::AwaitWithTimeout(const Condition& cond, absl::Duration timeout) {
return AwaitWithDeadline(
cond, synchronization_internal::DeadlineFromTimeout(timeout));
}
bool Mutex::LockWhenWithDeadline(const Condition& cond, absl::Time deadline) {
Lock();
return AwaitWithDeadline(cond, deadline);
}
bool Mutex::LockWhenWithTimeout(const Condition& cond, absl::Duration timeout) {
return LockWhenWithDeadline(
cond, synchronization_internal::DeadlineFromTimeout(timeout));
}
bool Mutex::ReaderLockWhenWithTimeout(const Condition& cond,
absl::Duration timeout) {
return LockWhenWithTimeout(cond, timeout);
}
bool Mutex::ReaderLockWhenWithDeadline(const Condition& cond,
absl::Time deadline) {
return LockWhenWithDeadline(cond, deadline);
}
void Mutex::EnableDebugLog(const char*) {}
void Mutex::EnableInvariantDebugging(void (*)(void*), void*) {}
void Mutex::ForgetDeadlockInfo() {}
void Mutex::AssertHeld() const {}
void Mutex::AssertReaderHeld() const {}
void Mutex::AssertNotHeld() const {}
CondVar::CondVar() {}
CondVar::~CondVar() {}
void CondVar::Signal() { impl()->Signal(); }
void CondVar::SignalAll() { impl()->SignalAll(); }
void CondVar::Wait(Mutex* mu) { return impl()->Wait(mu->impl()); }
bool CondVar::WaitWithDeadline(Mutex* mu, absl::Time deadline) {
return impl()->WaitWithDeadline(
mu->impl(), synchronization_internal::LimitedDeadline(deadline));
}
bool CondVar::WaitWithTimeout(Mutex* mu, absl::Duration timeout) {
return WaitWithDeadline(mu, absl::Now() + timeout);
}
void CondVar::EnableDebugLog(const char*) {}
#ifdef THREAD_SANITIZER
extern "C" void __tsan_read1(void *addr);
#else
#define __tsan_read1(addr) // do nothing if TSan not enabled
#endif
// A function that just returns its argument, dereferenced
static bool Dereference(void *arg) {
// ThreadSanitizer does not instrument this file for memory accesses.
// This function dereferences a user variable that can participate
// in a data race, so we need to manually tell TSan about this memory access.
__tsan_read1(arg);
return *(static_cast<bool *>(arg));
}
Condition::Condition() {} // null constructor, used for kTrue only
const Condition Condition::kTrue;
Condition::Condition(bool (*func)(void *), void *arg)
: eval_(&CallVoidPtrFunction),
function_(func),
method_(nullptr),
arg_(arg) {}
bool Condition::CallVoidPtrFunction(const Condition *c) {
return (*c->function_)(c->arg_);
}
Condition::Condition(const bool *cond)
: eval_(CallVoidPtrFunction),
function_(Dereference),
method_(nullptr),
// const_cast is safe since Dereference does not modify arg
arg_(const_cast<bool *>(cond)) {}
bool Condition::Eval() const {
// eval_ == null for kTrue
return (this->eval_ == nullptr) || (*this->eval_)(this);
}
} // namespace absl
