1 //
2 // Copyright 2016 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 "android.hardware.bluetooth@1.0-impl"
18
19 #include "async_fd_watcher.h"
20
21 #include <log/log.h>
22 #include <algorithm>
23 #include <atomic>
24 #include <condition_variable>
25 #include <map>
26 #include <mutex>
27 #include <thread>
28 #include <vector>
29 #include "fcntl.h"
30 #include "sys/select.h"
31 #include "unistd.h"
32
33 static const int INVALID_FD = -1;
34
35 static const int BT_RT_PRIORITY = 1;
36
37 namespace android {
38 namespace hardware {
39 namespace bluetooth {
40 namespace async {
41
WatchFdForNonBlockingReads(int file_descriptor,const ReadCallback & on_read_fd_ready_callback)42 int AsyncFdWatcher::WatchFdForNonBlockingReads(
43 int file_descriptor, const ReadCallback& on_read_fd_ready_callback) {
44 // Add file descriptor and callback
45 {
46 std::unique_lock<std::mutex> guard(internal_mutex_);
47 watched_fds_[file_descriptor] = on_read_fd_ready_callback;
48 }
49
50 // Start the thread if not started yet
51 return tryStartThread();
52 }
53
ConfigureTimeout(const std::chrono::milliseconds timeout,const TimeoutCallback & on_timeout_callback)54 int AsyncFdWatcher::ConfigureTimeout(
55 const std::chrono::milliseconds timeout,
56 const TimeoutCallback& on_timeout_callback) {
57 // Add timeout and callback
58 {
59 std::unique_lock<std::mutex> guard(timeout_mutex_);
60 timeout_cb_ = on_timeout_callback;
61 timeout_ms_ = timeout;
62 }
63
64 notifyThread();
65 return 0;
66 }
67
StopWatchingFileDescriptors()68 void AsyncFdWatcher::StopWatchingFileDescriptors() { stopThread(); }
69
~AsyncFdWatcher()70 AsyncFdWatcher::~AsyncFdWatcher() {}
71
72 // Make sure to call this with at least one file descriptor ready to be
73 // watched upon or the thread routine will return immediately
tryStartThread()74 int AsyncFdWatcher::tryStartThread() {
75 if (std::atomic_exchange(&running_, true)) return 0;
76
77 // Set up the communication channel
78 int pipe_fds[2];
79 if (pipe2(pipe_fds, O_NONBLOCK)) return -1;
80
81 notification_listen_fd_ = pipe_fds[0];
82 notification_write_fd_ = pipe_fds[1];
83
84 thread_ = std::thread([this]() { ThreadRoutine(); });
85 if (!thread_.joinable()) return -1;
86
87 return 0;
88 }
89
stopThread()90 int AsyncFdWatcher::stopThread() {
91 if (!std::atomic_exchange(&running_, false)) return 0;
92
93 notifyThread();
94 if (std::this_thread::get_id() != thread_.get_id()) {
95 thread_.join();
96 }
97
98 {
99 std::unique_lock<std::mutex> guard(internal_mutex_);
100 watched_fds_.clear();
101 }
102
103 {
104 std::unique_lock<std::mutex> guard(timeout_mutex_);
105 timeout_cb_ = nullptr;
106 }
107
108 close(notification_listen_fd_);
109 close(notification_write_fd_);
110
111 return 0;
112 }
113
notifyThread()114 int AsyncFdWatcher::notifyThread() {
115 uint8_t buffer[] = {0};
116 if (TEMP_FAILURE_RETRY(write(notification_write_fd_, &buffer, 1)) < 0) {
117 return -1;
118 }
119 return 0;
120 }
121
ThreadRoutine()122 void AsyncFdWatcher::ThreadRoutine() {
123 // Make watching thread RT.
124 struct sched_param rt_params;
125 rt_params.sched_priority = BT_RT_PRIORITY;
126 if (sched_setscheduler(gettid(), SCHED_FIFO, &rt_params)) {
127 ALOGE("%s unable to set SCHED_FIFO for pid %d, tid %d, error %s", __func__,
128 getpid(), gettid(), strerror(errno));
129 }
130
131 while (running_) {
132 fd_set read_fds;
133 FD_ZERO(&read_fds);
134 FD_SET(notification_listen_fd_, &read_fds);
135 int max_read_fd = INVALID_FD;
136 for (auto& it : watched_fds_) {
137 FD_SET(it.first, &read_fds);
138 max_read_fd = std::max(max_read_fd, it.first);
139 }
140
141 struct timeval timeout;
142 struct timeval* timeout_ptr = NULL;
143 if (timeout_ms_ > std::chrono::milliseconds(0)) {
144 timeout.tv_sec = timeout_ms_.count() / 1000;
145 timeout.tv_usec = (timeout_ms_.count() % 1000) * 1000;
146 timeout_ptr = &timeout;
147 }
148
149 // Wait until there is data available to read on some FD.
150 int nfds = std::max(notification_listen_fd_, max_read_fd);
151 int retval = select(nfds + 1, &read_fds, NULL, NULL, timeout_ptr);
152
153 // There was some error.
154 if (retval < 0) continue;
155
156 // Timeout.
157 if (retval == 0) {
158 // Allow the timeout callback to modify the timeout.
159 TimeoutCallback saved_cb;
160 {
161 std::unique_lock<std::mutex> guard(timeout_mutex_);
162 if (timeout_ms_ > std::chrono::milliseconds(0)) saved_cb = timeout_cb_;
163 }
164 if (saved_cb != nullptr) saved_cb();
165 continue;
166 }
167
168 // Read data from the notification FD.
169 if (FD_ISSET(notification_listen_fd_, &read_fds)) {
170 char buffer[] = {0};
171 TEMP_FAILURE_RETRY(read(notification_listen_fd_, buffer, 1));
172 continue;
173 }
174
175 // Invoke the data ready callbacks if appropriate.
176 {
177 // Hold the mutex to make sure that the callbacks are still valid.
178 std::unique_lock<std::mutex> guard(internal_mutex_);
179 for (auto& it : watched_fds_) {
180 if (FD_ISSET(it.first, &read_fds)) {
181 it.second(it.first);
182 }
183 }
184 }
185 }
186 }
187
188 } // namespace async
189 } // namespace bluetooth
190 } // namespace hardware
191 } // namespace android
192