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//
//
// 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 <grpc/support/port_platform.h>
#include "src/core/lib/gprpp/mpscq.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
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