1 /*
2 * Copyright (C) 2021 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #define LOG_TAG "FdTrigger"
18 #include <log/log.h>
19
20 #include "FdTrigger.h"
21
22 #include <poll.h>
23
24 #include <android-base/macros.h>
25
26 #include "RpcState.h"
27 namespace android {
28
make()29 std::unique_ptr<FdTrigger> FdTrigger::make() {
30 auto ret = std::make_unique<FdTrigger>();
31 if (!android::base::Pipe(&ret->mRead, &ret->mWrite)) {
32 ALOGE("Could not create pipe %s", strerror(errno));
33 return nullptr;
34 }
35 return ret;
36 }
37
trigger()38 void FdTrigger::trigger() {
39 mWrite.reset();
40 }
41
isTriggered()42 bool FdTrigger::isTriggered() {
43 return mWrite == -1;
44 }
45
triggerablePoll(base::borrowed_fd fd,int16_t event)46 status_t FdTrigger::triggerablePoll(base::borrowed_fd fd, int16_t event) {
47 LOG_ALWAYS_FATAL_IF(event == 0, "triggerablePoll %d with event 0 is not allowed", fd.get());
48 pollfd pfd[]{{.fd = fd.get(), .events = static_cast<int16_t>(event), .revents = 0},
49 {.fd = mRead.get(), .events = 0, .revents = 0}};
50 int ret = TEMP_FAILURE_RETRY(poll(pfd, arraysize(pfd), -1));
51 if (ret < 0) {
52 return -errno;
53 }
54 LOG_ALWAYS_FATAL_IF(ret == 0, "poll(%d) returns 0 with infinite timeout", fd.get());
55
56 // At least one FD has events. Check them.
57
58 // Detect explicit trigger(): DEAD_OBJECT
59 if (pfd[1].revents & POLLHUP) {
60 return DEAD_OBJECT;
61 }
62 // See unknown flags in trigger FD's revents (POLLERR / POLLNVAL).
63 // Treat this error condition as UNKNOWN_ERROR.
64 if (pfd[1].revents != 0) {
65 ALOGE("Unknown revents on trigger FD %d: revents = %d", pfd[1].fd, pfd[1].revents);
66 return UNKNOWN_ERROR;
67 }
68
69 // pfd[1].revents is 0, hence pfd[0].revents must be set, and only possible values are
70 // a subset of event | POLLHUP | POLLERR | POLLNVAL.
71
72 // POLLNVAL: invalid FD number, e.g. not opened.
73 if (pfd[0].revents & POLLNVAL) {
74 return BAD_VALUE;
75 }
76
77 // Error condition. It wouldn't be possible to do I/O on |fd| afterwards.
78 // Note: If this is the write end of a pipe then POLLHUP may also be set simultaneously. We
79 // still want DEAD_OBJECT in this case.
80 if (pfd[0].revents & POLLERR) {
81 LOG_RPC_DETAIL("poll() incoming FD %d results in revents = %d", pfd[0].fd, pfd[0].revents);
82 return DEAD_OBJECT;
83 }
84
85 // Success condition; event flag(s) set. Even though POLLHUP may also be set,
86 // treat it as a success condition to ensure data is drained.
87 if (pfd[0].revents & event) {
88 return OK;
89 }
90
91 // POLLHUP: Peer closed connection. Treat as DEAD_OBJECT.
92 // This is a very common case, so don't log.
93 return DEAD_OBJECT;
94 }
95
96 } // namespace android
97