| // |
| // |
| // Copyright 2016 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 "src/core/lib/gprpp/mpscq.h" |
| |
| #include <grpc/support/port_platform.h> |
| |
| namespace grpc_core { |
| |
| // |
| // MultiProducerSingleConsumerQueue |
| // |
| |
| bool MultiProducerSingleConsumerQueue::Push(Node* node) { |
| node->next.store(nullptr, std::memory_order_relaxed); |
| Node* prev = head_.exchange(node, std::memory_order_acq_rel); |
| prev->next.store(node, std::memory_order_release); |
| return prev == &stub_; |
| } |
| |
| MultiProducerSingleConsumerQueue::Node* |
| MultiProducerSingleConsumerQueue::Pop() { |
| bool empty; |
| return PopAndCheckEnd(&empty); |
| } |
| |
| MultiProducerSingleConsumerQueue::Node* |
| MultiProducerSingleConsumerQueue::PopAndCheckEnd(bool* empty) { |
| Node* tail = tail_; |
| Node* next = tail_->next.load(std::memory_order_acquire); |
| if (tail == &stub_) { |
| // indicates the list is actually (ephemerally) empty |
| if (next == nullptr) { |
| *empty = true; |
| return nullptr; |
| } |
| tail_ = next; |
| tail = next; |
| next = tail->next.load(std::memory_order_acquire); |
| } |
| if (next != nullptr) { |
| *empty = false; |
| tail_ = next; |
| return tail; |
| } |
| Node* head = head_.load(std::memory_order_acquire); |
| if (tail != head) { |
| *empty = false; |
| // indicates a retry is in order: we're still adding |
| return nullptr; |
| } |
| Push(&stub_); |
| next = tail->next.load(std::memory_order_acquire); |
| if (next != nullptr) { |
| *empty = false; |
| tail_ = next; |
| return tail; |
| } |
| // indicates a retry is in order: we're still adding |
| *empty = false; |
| return nullptr; |
| } |
| |
| // |
| // LockedMultiProducerSingleConsumerQueue |
| // |
| |
| bool LockedMultiProducerSingleConsumerQueue::Push(Node* node) { |
| return queue_.Push(node); |
| } |
| |
| LockedMultiProducerSingleConsumerQueue::Node* |
| LockedMultiProducerSingleConsumerQueue::TryPop() { |
| if (mu_.TryLock()) { |
| Node* node = queue_.Pop(); |
| mu_.Unlock(); |
| return node; |
| } |
| return nullptr; |
| } |
| |
| LockedMultiProducerSingleConsumerQueue::Node* |
| LockedMultiProducerSingleConsumerQueue::Pop() { |
| MutexLock lock(&mu_); |
| bool empty = false; |
| Node* node; |
| do { |
| node = queue_.PopAndCheckEnd(&empty); |
| } while (node == nullptr && !empty); |
| return node; |
| } |
| |
| } // namespace grpc_core |