905a5df83d
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
93 lines
2.9 KiB
C++
93 lines
2.9 KiB
C++
/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "epoll.h"
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#include <stdint.h>
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#include <sys/epoll.h>
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#include <chrono>
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#include <functional>
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#include <map>
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namespace android {
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namespace init {
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Epoll::Epoll() {}
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Result<void> Epoll::Open() {
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if (epoll_fd_ >= 0) return {};
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epoll_fd_.reset(epoll_create1(EPOLL_CLOEXEC));
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if (epoll_fd_ == -1) {
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return ErrnoError() << "epoll_create1 failed";
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}
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return {};
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}
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Result<void> Epoll::RegisterHandler(int fd, std::function<void()> handler, uint32_t events) {
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if (!events) {
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return Error() << "Must specify events";
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}
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auto [it, inserted] = epoll_handlers_.emplace(fd, std::move(handler));
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if (!inserted) {
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return Error() << "Cannot specify two epoll handlers for a given FD";
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}
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epoll_event ev;
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ev.events = events;
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// std::map's iterators do not get invalidated until erased, so we use the
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// pointer to the std::function in the map directly for epoll_ctl.
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ev.data.ptr = reinterpret_cast<void*>(&it->second);
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if (epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, fd, &ev) == -1) {
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Result<void> result = ErrnoError() << "epoll_ctl failed to add fd";
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epoll_handlers_.erase(fd);
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return result;
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}
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return {};
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}
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Result<void> Epoll::UnregisterHandler(int fd) {
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if (epoll_ctl(epoll_fd_, EPOLL_CTL_DEL, fd, nullptr) == -1) {
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return ErrnoError() << "epoll_ctl failed to remove fd";
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}
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if (epoll_handlers_.erase(fd) != 1) {
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return Error() << "Attempting to remove epoll handler for FD without an existing handler";
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}
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return {};
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}
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Result<std::vector<std::function<void()>*>> Epoll::Wait(
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std::optional<std::chrono::milliseconds> timeout) {
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int timeout_ms = -1;
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if (timeout && timeout->count() < INT_MAX) {
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timeout_ms = timeout->count();
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}
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const auto max_events = epoll_handlers_.size();
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epoll_event ev[max_events];
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auto num_events = TEMP_FAILURE_RETRY(epoll_wait(epoll_fd_, ev, max_events, timeout_ms));
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if (num_events == -1) {
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return ErrnoError() << "epoll_wait failed";
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}
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std::vector<std::function<void()>*> pending_functions;
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for (int i = 0; i < num_events; ++i) {
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pending_functions.emplace_back(reinterpret_cast<std::function<void()>*>(ev[i].data.ptr));
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}
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return pending_functions;
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}
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} // namespace init
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} // namespace android
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