92 lines
2.6 KiB
C++
92 lines
2.6 KiB
C++
// Copyright 2023 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "absl/synchronization/internal/stdcpp_waiter.h"
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#ifdef ABSL_INTERNAL_HAVE_STDCPP_WAITER
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#include <chrono> // NOLINT(build/c++11)
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#include <condition_variable> // NOLINT(build/c++11)
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#include <mutex> // NOLINT(build/c++11)
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#include "absl/base/config.h"
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#include "absl/base/internal/raw_logging.h"
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#include "absl/base/internal/thread_identity.h"
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#include "absl/base/optimization.h"
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#include "absl/synchronization/internal/kernel_timeout.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace synchronization_internal {
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#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
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constexpr char StdcppWaiter::kName[];
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#endif
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StdcppWaiter::StdcppWaiter() : waiter_count_(0), wakeup_count_(0) {}
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bool StdcppWaiter::Wait(KernelTimeout t) {
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std::unique_lock<std::mutex> lock(mu_);
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++waiter_count_;
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// Loop until we find a wakeup to consume or timeout.
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// Note that, since the thread ticker is just reset, we don't need to check
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// whether the thread is idle on the very first pass of the loop.
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bool first_pass = true;
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while (wakeup_count_ == 0) {
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if (!first_pass) MaybeBecomeIdle();
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// No wakeups available, time to wait.
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if (!t.has_timeout()) {
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cv_.wait(lock);
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} else {
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auto wait_result = t.SupportsSteadyClock() && t.is_relative_timeout()
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? cv_.wait_for(lock, t.ToChronoDuration())
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: cv_.wait_until(lock, t.ToChronoTimePoint());
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if (wait_result == std::cv_status::timeout) {
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--waiter_count_;
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return false;
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}
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}
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first_pass = false;
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}
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// Consume a wakeup and we're done.
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--wakeup_count_;
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--waiter_count_;
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return true;
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}
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void StdcppWaiter::Post() {
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std::lock_guard<std::mutex> lock(mu_);
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++wakeup_count_;
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InternalCondVarPoke();
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}
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void StdcppWaiter::Poke() {
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std::lock_guard<std::mutex> lock(mu_);
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InternalCondVarPoke();
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}
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void StdcppWaiter::InternalCondVarPoke() {
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if (waiter_count_ != 0) {
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cv_.notify_one();
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}
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}
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} // namespace synchronization_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_INTERNAL_HAVE_STDCPP_WAITER
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