| /* |
| * |
| * Copyright 2015 gRPC 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. |
| * |
| */ |
| |
| #include <grpc/support/port_platform.h> |
| |
| #include "src/core/lib/event_engine/thread_pool.h" |
| |
| #include <utility> |
| |
| #include "src/core/lib/gprpp/thd.h" |
| |
| namespace grpc_event_engine { |
| namespace experimental { |
| |
| ThreadPool::Thread::Thread(ThreadPool* pool) |
| : pool_(pool), |
| thd_( |
| "posix_eventengine_pool", |
| [](void* th) { static_cast<ThreadPool::Thread*>(th)->ThreadFunc(); }, |
| this, nullptr, grpc_core::Thread::Options().set_tracked(false)) { |
| thd_.Start(); |
| } |
| ThreadPool::Thread::~Thread() { thd_.Join(); } |
| |
| void ThreadPool::Thread::ThreadFunc() { |
| pool_->ThreadFunc(); |
| // Now that we have killed ourselves, we should reduce the thread count |
| grpc_core::MutexLock lock(&pool_->mu_); |
| pool_->nthreads_--; |
| // Move ourselves to dead list |
| pool_->dead_threads_.push_back(this); |
| |
| if (pool_->nthreads_ == 0) { |
| if (pool_->forking_) pool_->fork_cv_.Signal(); |
| if (pool_->shutdown_) pool_->shutdown_cv_.Signal(); |
| } |
| } |
| |
| void ThreadPool::ThreadFunc() { |
| for (;;) { |
| // Wait until work is available or we are shutting down. |
| grpc_core::ReleasableMutexLock lock(&mu_); |
| if (!forking_ && !shutdown_ && callbacks_.empty()) { |
| // If there are too many threads waiting, then quit this thread |
| if (threads_waiting_ >= reserve_threads_) { |
| break; |
| } |
| threads_waiting_++; |
| cv_.Wait(&mu_); |
| threads_waiting_--; |
| } |
| // a fork could be initiated while the thread was waiting |
| if (forking_) return; |
| // Drain callbacks before considering shutdown to ensure all work |
| // gets completed. |
| if (!callbacks_.empty()) { |
| auto cb = std::move(callbacks_.front()); |
| callbacks_.pop(); |
| lock.Release(); |
| cb(); |
| } else if (shutdown_) { |
| break; |
| } |
| } |
| } |
| |
| ThreadPool::ThreadPool(int reserve_threads) |
| : shutdown_(false), |
| reserve_threads_(reserve_threads), |
| nthreads_(0), |
| threads_waiting_(0), |
| forking_(false) { |
| grpc_core::MutexLock lock(&mu_); |
| StartNThreadsLocked(reserve_threads_); |
| } |
| |
| void ThreadPool::StartNThreadsLocked(int n) { |
| for (int i = 0; i < n; i++) { |
| nthreads_++; |
| new Thread(this); |
| } |
| } |
| |
| void ThreadPool::ReapThreads(std::vector<Thread*>* tlist) { |
| for (auto* t : *tlist) delete t; |
| tlist->clear(); |
| } |
| |
| ThreadPool::~ThreadPool() { |
| grpc_core::MutexLock lock(&mu_); |
| shutdown_ = true; |
| cv_.SignalAll(); |
| while (nthreads_ != 0) { |
| shutdown_cv_.Wait(&mu_); |
| } |
| ReapThreads(&dead_threads_); |
| } |
| |
| void ThreadPool::Add(absl::AnyInvocable<void()> callback) { |
| grpc_core::MutexLock lock(&mu_); |
| // Add works to the callbacks list |
| callbacks_.push(std::move(callback)); |
| // Store the callback for later if we are forking. |
| // TODO(hork): should we block instead? |
| if (forking_) return; |
| // Increase pool size or notify as needed |
| if (threads_waiting_ == 0) { |
| // Kick off a new thread |
| nthreads_++; |
| new Thread(this); |
| } else { |
| cv_.Signal(); |
| } |
| // Also use this chance to harvest dead threads |
| if (!dead_threads_.empty()) { |
| ReapThreads(&dead_threads_); |
| } |
| } |
| |
| void ThreadPool::PrepareFork() { |
| grpc_core::MutexLock lock(&mu_); |
| forking_ = true; |
| cv_.SignalAll(); |
| while (nthreads_ != 0) { |
| fork_cv_.Wait(&mu_); |
| } |
| ReapThreads(&dead_threads_); |
| } |
| |
| void ThreadPool::PostforkParent() { |
| grpc_core::MutexLock lock(&mu_); |
| forking_ = false; |
| StartNThreadsLocked(reserve_threads_); |
| } |
| |
| void ThreadPool::PostforkChild() { |
| grpc_core::MutexLock lock(&mu_); |
| forking_ = false; |
| StartNThreadsLocked(reserve_threads_); |
| } |
| |
| } // namespace experimental |
| } // namespace grpc_event_engine |