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main
util/single_thread_executor.h
57 строк
2 KB
Chad Austin
add a missing include (#11624)
19 июл 2023, 01:38
19 июл 2023, 01:38
ff0d618
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// Copyright (c) Meta Platforms, Inc. and affiliates. // // This source code is licensed under both the GPLv2 (found in the // COPYING file in the root directory) and Apache 2.0 License // (found in the LICENSE.Apache file in the root directory). // #pragma once #if USE_COROUTINES #include <atomic> #include <queue> #include "folly/CPortability.h" #include "folly/CppAttributes.h" #include "folly/Executor.h" #include "util/async_file_reader.h" namespace ROCKSDB_NAMESPACE { // Implements a simple executor that runs callback functions in the same // thread, unlike CPUThreadExecutor which may schedule the callback on // another thread. Runs in a tight loop calling the queued callbacks, // and polls for async IO completions when idle. The completions will // resume suspended coroutines and they get added to the queue, which // will get picked up by this loop. // Any possibility of deadlock is precluded because the file system // guarantees that async IO completion callbacks will not be scheduled // to run in this thread or this executor. class SingleThreadExecutor : public folly::Executor { public: explicit SingleThreadExecutor(AsyncFileReader& reader) : reader_(reader), busy_(false) {} void add(folly::Func callback) override { auto& q = q_; q.push(std::move(callback)); if (q.size() == 1 && !busy_) { while (!q.empty()) { q.front()(); q.pop(); if (q.empty()) { // Prevent recursion, as the Wait may queue resumed coroutines busy_ = true; reader_.Wait(); busy_ = false; } } } } private: std::queue<folly::Func> q_; AsyncFileReader& reader_; bool busy_; }; } // namespace ROCKSDB_NAMESPACE #endif // USE_COROUTINES