97 lines
3.1 KiB
C++
97 lines
3.1 KiB
C++
/*
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* Copyright (C) 2021 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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#define LOG_TAG "FdTrigger"
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#include <log/log.h>
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#include "FdTrigger.h"
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#include <poll.h>
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#include <android-base/macros.h>
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#include "RpcState.h"
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namespace android {
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std::unique_ptr<FdTrigger> FdTrigger::make() {
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auto ret = std::make_unique<FdTrigger>();
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if (!android::base::Pipe(&ret->mRead, &ret->mWrite)) {
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ALOGE("Could not create pipe %s", strerror(errno));
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return nullptr;
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}
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return ret;
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}
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void FdTrigger::trigger() {
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mWrite.reset();
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}
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bool FdTrigger::isTriggered() {
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return mWrite == -1;
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}
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status_t FdTrigger::triggerablePoll(base::borrowed_fd fd, int16_t event) {
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LOG_ALWAYS_FATAL_IF(event == 0, "triggerablePoll %d with event 0 is not allowed", fd.get());
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pollfd pfd[]{{.fd = fd.get(), .events = static_cast<int16_t>(event), .revents = 0},
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{.fd = mRead.get(), .events = 0, .revents = 0}};
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int ret = TEMP_FAILURE_RETRY(poll(pfd, arraysize(pfd), -1));
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if (ret < 0) {
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return -errno;
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}
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LOG_ALWAYS_FATAL_IF(ret == 0, "poll(%d) returns 0 with infinite timeout", fd.get());
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// At least one FD has events. Check them.
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// Detect explicit trigger(): DEAD_OBJECT
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if (pfd[1].revents & POLLHUP) {
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return DEAD_OBJECT;
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}
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// See unknown flags in trigger FD's revents (POLLERR / POLLNVAL).
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// Treat this error condition as UNKNOWN_ERROR.
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if (pfd[1].revents != 0) {
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ALOGE("Unknown revents on trigger FD %d: revents = %d", pfd[1].fd, pfd[1].revents);
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return UNKNOWN_ERROR;
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}
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// pfd[1].revents is 0, hence pfd[0].revents must be set, and only possible values are
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// a subset of event | POLLHUP | POLLERR | POLLNVAL.
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// POLLNVAL: invalid FD number, e.g. not opened.
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if (pfd[0].revents & POLLNVAL) {
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return BAD_VALUE;
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}
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// Error condition. It wouldn't be possible to do I/O on |fd| afterwards.
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// Note: If this is the write end of a pipe then POLLHUP may also be set simultaneously. We
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// still want DEAD_OBJECT in this case.
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if (pfd[0].revents & POLLERR) {
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LOG_RPC_DETAIL("poll() incoming FD %d results in revents = %d", pfd[0].fd, pfd[0].revents);
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return DEAD_OBJECT;
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}
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// Success condition; event flag(s) set. Even though POLLHUP may also be set,
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// treat it as a success condition to ensure data is drained.
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if (pfd[0].revents & event) {
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return OK;
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}
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// POLLHUP: Peer closed connection. Treat as DEAD_OBJECT.
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// This is a very common case, so don't log.
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return DEAD_OBJECT;
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}
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} // namespace android
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