platform_system_core/init/epoll.h
Tom Cherry 905a5df83d init: Always reap processes before handling properties
There is a race that manifests like this:

1) A service dies (not processed by init yet).
2) service_manager processes death notification.
3) service_manager gets checkService and calls init to start service.
4) init gets the ctl.start / ctl.interface_start for the service
   but the service already appears started, so it does nothing.
5) init gets sigchld, but doesn't do anything else to restart the
   service

We can avoid all of this if we already reap pending processes before
handling properties in the main loop of init.  Since reaping the
services calls waitid(), there's no race even if the signalfd for
sigchld hasn't triggered yet.  It also won't cost us much efficiency,
since it's only a single system call.

Test: CF boots, init unit tests pass
Change-Id: Ie24ef406055b283797b41b1821c8ebcccead4db4
2019-08-30 14:20:05 -07:00

51 lines
1.3 KiB
C++

/*
* Copyright (C) 2018 The Android Open Source Project
*
* 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.
*/
#pragma once
#include <stdint.h>
#include <sys/epoll.h>
#include <chrono>
#include <functional>
#include <map>
#include <optional>
#include <vector>
#include <android-base/unique_fd.h>
#include "result.h"
namespace android {
namespace init {
class Epoll {
public:
Epoll();
Result<void> Open();
Result<void> RegisterHandler(int fd, std::function<void()> handler, uint32_t events = EPOLLIN);
Result<void> UnregisterHandler(int fd);
Result<std::vector<std::function<void()>*>> Wait(
std::optional<std::chrono::milliseconds> timeout);
private:
android::base::unique_fd epoll_fd_;
std::map<int, std::function<void()>> epoll_handlers_;
};
} // namespace init
} // namespace android