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