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/**
* Copyright (C) 2020-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/util/out_of_line_executor.h"
namespace mongo {
/**
* An "OutOfLineExecutor" that actually runs on the same thread of execution
* This executor is not thread-safe, and accessing it by multiple threads is prohibited.
* Multi-threaded accesses to instances of "InlineQueuedCountingExecutor" result in undefined
* behavior.
*/
class InlineQueuedCountingExecutor : public OutOfLineExecutor {
public:
void schedule(Task task) override {
// Add the task to our queue
taskQueue.emplace_back(std::move(task));
// Make sure that we are not invocing a Task while invocing a Task. Some OutOfLineExecutors
// do recursively dispatch Tasks, however, they also carefully monitor stack depth. For the
// purposes of testing, let's serialize our Tasks. One Task runs at a time.
if (std::exchange(inSchedule, true)) {
return;
}
ON_BLOCK_EXIT([this] {
// Admit we're not working on the queue anymore
inSchedule = false;
});
// Clear out our queue
while (!taskQueue.empty()) {
auto task = std::move(taskQueue.front());
// Relaxed to avoid adding synchronization where there otherwise wouldn't be. That would
// cause a false negative from TSAN.
tasksRun.fetch_add(1, std::memory_order_relaxed);
task(Status::OK());
taskQueue.pop_front();
}
}
static auto make() {
return std::make_shared<InlineQueuedCountingExecutor>();
}
bool inSchedule;
std::deque<Task> taskQueue;
std::atomic<uint32_t> tasksRun{0}; // NOLINT
};
class InlineRecursiveCountingExecutor final : public OutOfLineExecutor {
public:
void schedule(Task task) noexcept override {
// Relaxed to avoid adding synchronization where there otherwise wouldn't be. That would
// cause a false negative from TSAN.
tasksRun.fetch_add(1, std::memory_order_relaxed);
task(Status::OK());
}
static auto make() {
return std::make_shared<InlineRecursiveCountingExecutor>();
}
std::atomic<uint32_t> tasksRun{0}; // NOLINT
};
class RejectingExecutor final : public OutOfLineExecutor {
public:
void schedule(Task task) noexcept override {
// Relaxed to avoid adding synchronization where there otherwise wouldn't be. That would
// cause a false negative from TSAN.
tasksRejected.fetch_add(1, std::memory_order_relaxed);
task(Status(ErrorCodes::ShutdownInProgress, ""));
}
static auto make() {
return std::make_shared<RejectingExecutor>();
}
std::atomic<uint32_t> tasksRejected{0}; // NOLINT
};
} // namespace mongo
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