107 lines
3.7 KiB
C++
107 lines
3.7 KiB
C++
// Copyright 2017 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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// This file is a no-op if the required LowLevelAlloc support is missing.
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#include "absl/base/internal/low_level_alloc.h"
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#ifndef ABSL_LOW_LEVEL_ALLOC_MISSING
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#include "absl/synchronization/internal/per_thread_sem.h"
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#include <atomic>
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#include "absl/base/attributes.h"
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#include "absl/base/internal/thread_identity.h"
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#include "absl/synchronization/internal/waiter.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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void PerThreadSem::SetThreadBlockedCounter(std::atomic<int> *counter) {
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base_internal::ThreadIdentity *identity;
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identity = GetOrCreateCurrentThreadIdentity();
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identity->blocked_count_ptr = counter;
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}
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std::atomic<int> *PerThreadSem::GetThreadBlockedCounter() {
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base_internal::ThreadIdentity *identity;
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identity = GetOrCreateCurrentThreadIdentity();
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return identity->blocked_count_ptr;
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}
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void PerThreadSem::Init(base_internal::ThreadIdentity *identity) {
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new (Waiter::GetWaiter(identity)) Waiter();
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identity->ticker.store(0, std::memory_order_relaxed);
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identity->wait_start.store(0, std::memory_order_relaxed);
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identity->is_idle.store(false, std::memory_order_relaxed);
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}
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void PerThreadSem::Destroy(base_internal::ThreadIdentity *identity) {
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Waiter::GetWaiter(identity)->~Waiter();
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}
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void PerThreadSem::Tick(base_internal::ThreadIdentity *identity) {
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const int ticker =
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identity->ticker.fetch_add(1, std::memory_order_relaxed) + 1;
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const int wait_start = identity->wait_start.load(std::memory_order_relaxed);
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const bool is_idle = identity->is_idle.load(std::memory_order_relaxed);
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if (wait_start && (ticker - wait_start > Waiter::kIdlePeriods) && !is_idle) {
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// Wakeup the waiting thread since it is time for it to become idle.
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Waiter::GetWaiter(identity)->Poke();
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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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extern "C" {
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ABSL_ATTRIBUTE_WEAK void AbslInternalPerThreadSemPost(
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absl::base_internal::ThreadIdentity *identity) {
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absl::synchronization_internal::Waiter::GetWaiter(identity)->Post();
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}
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ABSL_ATTRIBUTE_WEAK bool AbslInternalPerThreadSemWait(
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absl::synchronization_internal::KernelTimeout t) {
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bool timeout = false;
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absl::base_internal::ThreadIdentity *identity;
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identity = absl::synchronization_internal::GetOrCreateCurrentThreadIdentity();
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// Ensure wait_start != 0.
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int ticker = identity->ticker.load(std::memory_order_relaxed);
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identity->wait_start.store(ticker ? ticker : 1, std::memory_order_relaxed);
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identity->is_idle.store(false, std::memory_order_relaxed);
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if (identity->blocked_count_ptr != nullptr) {
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// Increment count of threads blocked in a given thread pool.
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identity->blocked_count_ptr->fetch_add(1, std::memory_order_relaxed);
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}
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timeout =
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!absl::synchronization_internal::Waiter::GetWaiter(identity)->Wait(t);
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if (identity->blocked_count_ptr != nullptr) {
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identity->blocked_count_ptr->fetch_sub(1, std::memory_order_relaxed);
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}
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identity->is_idle.store(false, std::memory_order_relaxed);
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identity->wait_start.store(0, std::memory_order_relaxed);
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return !timeout;
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}
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} // extern "C"
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#endif // ABSL_LOW_LEVEL_ALLOC_MISSING
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