1 /*
2 * Copyright (C) 2020 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 #include "host/frontend/webrtc/kernel_log_events_handler.h"
18
19 #include <android-base/logging.h>
20
21 #include <common/libs/fs/shared_select.h>
22 #include <host/commands/kernel_log_monitor/kernel_log_server.h>
23 #include <host/commands/kernel_log_monitor/utils.h>
24 #include <host/libs/config/cuttlefish_config.h>
25
26 using namespace android;
27
28 namespace cuttlefish {
29
KernelLogEventsHandler(SharedFD kernel_log_fd)30 KernelLogEventsHandler::KernelLogEventsHandler(
31 SharedFD kernel_log_fd)
32 : kernel_log_fd_(kernel_log_fd),
33 eventfd_(SharedFD::Event()),
34 running_(true),
35 read_thread_([this]() { ReadLoop(); }) {}
36
~KernelLogEventsHandler()37 KernelLogEventsHandler::~KernelLogEventsHandler() {
38 running_ = false;
39 eventfd_->EventfdWrite(1);
40 read_thread_.join();
41 }
42
ReadLoop()43 void KernelLogEventsHandler::ReadLoop() {
44 CHECK(eventfd_->IsOpen()) << "Failed to create event fd: "
45 << eventfd_->StrError();
46 while (running_) {
47 SharedFDSet read_set;
48 read_set.Set(eventfd_);
49 read_set.Set(kernel_log_fd_);
50 auto select_ret = Select(&read_set, nullptr, nullptr, nullptr);
51 if (select_ret < 0) {
52 LOG(ERROR) << "Error on select call";
53 break;
54 }
55 if (read_set.IsSet(eventfd_)) {
56 eventfd_t evt;
57 (void)eventfd_->EventfdRead(&evt);
58 if (!running_) {
59 // There won't be anyone listening for kernel log events if the thread
60 // was asked to stop, so break out of the loop without reading.
61 break;
62 }
63 }
64 if (read_set.IsSet(kernel_log_fd_)) {
65 Result<std::optional<monitor::ReadEventResult>> read_result =
66 monitor::ReadEvent(kernel_log_fd_);
67 if (!read_result) {
68 LOG(ERROR) << "Failed to read kernel log event: "
69 << read_result.error().FormatForEnv();
70 break;
71 } else if (!(*read_result)) {
72 LOG(ERROR) << "EOF from kernel_log_monitor";
73 break;
74 }
75
76 if ((*read_result)->event == monitor::Event::BootStarted) {
77 Json::Value message;
78 message["event"] = kBootStartedMessage;
79 DeliverEvent(message);
80 }
81 if ((*read_result)->event == monitor::Event::BootCompleted) {
82 Json::Value message;
83 message["event"] = kBootCompletedMessage;
84 DeliverEvent(message);
85 }
86 if ((*read_result)->event == monitor::Event::ScreenChanged) {
87 Json::Value message;
88 message["event"] = kScreenChangedMessage;
89 message["metadata"] = (*read_result)->metadata;
90 DeliverEvent(message);
91 }
92 if ((*read_result)->event == monitor::Event::DisplayPowerModeChanged) {
93 Json::Value message;
94 message["event"] = kDisplayPowerModeChangedMessage;
95 message["metadata"] = (*read_result)->metadata;
96 DeliverEvent(message);
97 }
98 }
99 }
100 }
101
AddSubscriber(std::function<void (const Json::Value &)> subscriber)102 int KernelLogEventsHandler::AddSubscriber(
103 std::function<void(const Json::Value&)> subscriber) {
104 std::lock_guard<std::mutex> lock(subscribers_mtx_);
105 for (const auto& event : last_events_) {
106 // Deliver the last event of each type to the new subscriber so that it can
107 // show the correct state.
108 subscriber(event);
109 }
110 subscribers_[++last_subscriber_id_] = subscriber;
111 return last_subscriber_id_;
112 }
113
Unsubscribe(int subscriber_id)114 void KernelLogEventsHandler::Unsubscribe(int subscriber_id) {
115 std::lock_guard<std::mutex> lock(subscribers_mtx_);
116 subscribers_.erase(subscriber_id);
117 }
118
DeliverEvent(const Json::Value & event)119 void KernelLogEventsHandler::DeliverEvent(const Json::Value& event) {
120 std::lock_guard<std::mutex> lock(subscribers_mtx_);
121 // event["event"] is actually the type of the event.
122 // This would be more efficient with a set, but a list maintains the order in
123 // which events arrived. And for just a handful of elements the list can
124 // actually perform better.
125 for (auto it = last_events_.begin();
126 it != last_events_.end(); it++) {
127 if ((*it)["event"].asString() == event["event"].asString()) {
128 last_events_.erase(it);
129 break;
130 }
131 }
132 last_events_.push_back(event);
133 for (const auto& entry : subscribers_) {
134 entry.second(event);
135 }
136 }
137
138 } // namespace cuttlefish
139