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// Copyright 2023 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
//
// https://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 "absl/synchronization/internal/pthread_waiter.h"
#ifdef ABSL_INTERNAL_HAVE_PTHREAD_WAITER
#include <pthread.h>
#include <sys/time.h>
#include <unistd.h>
#include <cassert>
#include <cerrno>
#include "absl/base/config.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/internal/thread_identity.h"
#include "absl/base/optimization.h"
#include "absl/synchronization/internal/kernel_timeout.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace synchronization_internal {
namespace {
class PthreadMutexHolder {
public:
explicit PthreadMutexHolder(pthread_mutex_t *mu) : mu_(mu) {
const int err = pthread_mutex_lock(mu_);
if (err != 0) {
ABSL_RAW_LOG(FATAL, "pthread_mutex_lock failed: %d", err);
}
}
PthreadMutexHolder(const PthreadMutexHolder &rhs) = delete;
PthreadMutexHolder &operator=(const PthreadMutexHolder &rhs) = delete;
~PthreadMutexHolder() {
const int err = pthread_mutex_unlock(mu_);
if (err != 0) {
ABSL_RAW_LOG(FATAL, "pthread_mutex_unlock failed: %d", err);
}
}
private:
pthread_mutex_t *mu_;
};
} // namespace
#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
constexpr char PthreadWaiter::kName[];
#endif
PthreadWaiter::PthreadWaiter() : waiter_count_(0), wakeup_count_(0) {
const int err = pthread_mutex_init(&mu_, 0);
if (err != 0) {
ABSL_RAW_LOG(FATAL, "pthread_mutex_init failed: %d", err);
}
const int err2 = pthread_cond_init(&cv_, 0);
if (err2 != 0) {
ABSL_RAW_LOG(FATAL, "pthread_cond_init failed: %d", err2);
}
}
#ifdef __APPLE__
#define ABSL_INTERNAL_HAS_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP 1
#endif
#if defined(__GLIBC__) && \
(__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 30))
#define ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT 1
#elif defined(__ANDROID_API__) && __ANDROID_API__ >= 30
#define ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT 1
#endif
// Calls pthread_cond_timedwait() or possibly something else like
// pthread_cond_timedwait_relative_np() depending on the platform and
// KernelTimeout requested. The return value is the same as the return
// value of pthread_cond_timedwait().
int PthreadWaiter::TimedWait(KernelTimeout t) {
assert(t.has_timeout());
if (KernelTimeout::SupportsSteadyClock() && t.is_relative_timeout()) {
#ifdef ABSL_INTERNAL_HAS_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP
const auto rel_timeout = t.MakeRelativeTimespec();
return pthread_cond_timedwait_relative_np(&cv_, &mu_, &rel_timeout);
#elif defined(ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT) && \
defined(CLOCK_MONOTONIC)
const auto abs_clock_timeout = t.MakeClockAbsoluteTimespec(CLOCK_MONOTONIC);
return pthread_cond_clockwait(&cv_, &mu_, CLOCK_MONOTONIC,
&abs_clock_timeout);
#endif
}
const auto abs_timeout = t.MakeAbsTimespec();
return pthread_cond_timedwait(&cv_, &mu_, &abs_timeout);
}
bool PthreadWaiter::Wait(KernelTimeout t) {
PthreadMutexHolder h(&mu_);
++waiter_count_;
// Loop until we find a wakeup to consume or timeout.
// Note that, since the thread ticker is just reset, we don't need to check
// whether the thread is idle on the very first pass of the loop.
bool first_pass = true;
while (wakeup_count_ == 0) {
if (!first_pass) MaybeBecomeIdle();
// No wakeups available, time to wait.
if (!t.has_timeout()) {
const int err = pthread_cond_wait(&cv_, &mu_);
if (err != 0) {
ABSL_RAW_LOG(FATAL, "pthread_cond_wait failed: %d", err);
}
} else {
const int err = TimedWait(t);
if (err == ETIMEDOUT) {
--waiter_count_;
return false;
}
if (err != 0) {
ABSL_RAW_LOG(FATAL, "PthreadWaiter::TimedWait() failed: %d", err);
}
}
first_pass = false;
}
// Consume a wakeup and we're done.
--wakeup_count_;
--waiter_count_;
return true;
}
void PthreadWaiter::Post() {
PthreadMutexHolder h(&mu_);
++wakeup_count_;
InternalCondVarPoke();
}
void PthreadWaiter::Poke() {
PthreadMutexHolder h(&mu_);
InternalCondVarPoke();
}
void PthreadWaiter::InternalCondVarPoke() {
if (waiter_count_ != 0) {
const int err = pthread_cond_signal(&cv_);
if (ABSL_PREDICT_FALSE(err != 0)) {
ABSL_RAW_LOG(FATAL, "pthread_cond_signal failed: %d", err);
}
}
}
} // namespace synchronization_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_INTERNAL_HAVE_PTHREAD_WAITER
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