1#include "epoll_event_dispatcher.h"
2
3#include <log/log.h>
4#include <sys/epoll.h>
5#include <sys/eventfd.h>
6#include <sys/prctl.h>
7
8#include <dvr/performance_client_api.h>
9
10namespace android {
11namespace dvr {
12
13EpollEventDispatcher::EpollEventDispatcher() {
14  epoll_fd_.Reset(epoll_create(64));
15  if (!epoll_fd_) {
16    ALOGE("Failed to create epoll fd: %s", strerror(errno));
17    return;
18  }
19
20  event_fd_.Reset(eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK));
21  if (!event_fd_) {
22    ALOGE("Failed to create event for epolling: %s", strerror(errno));
23    return;
24  }
25
26  // Add watch for eventfd. This should only watch for EPOLLIN, which gets set
27  // when eventfd_write occurs. Use "this" as a unique sentinal value to
28  // identify events from the event fd.
29  epoll_event event = {.events = EPOLLIN, .data = {.ptr = this}};
30  if (epoll_ctl(epoll_fd_.Get(), EPOLL_CTL_ADD, event_fd_.Get(), &event) < 0) {
31    ALOGE("Failed to add eventfd to epoll set because: %s", strerror(errno));
32    return;
33  }
34
35  thread_ = std::thread(&EpollEventDispatcher::EventThread, this);
36}
37
38EpollEventDispatcher::~EpollEventDispatcher() { Stop(); }
39
40void EpollEventDispatcher::Stop() {
41  exit_thread_.store(true);
42  eventfd_write(event_fd_.Get(), 1);
43}
44
45pdx::Status<void> EpollEventDispatcher::AddEventHandler(int fd, int event_mask,
46                                                        Handler handler) {
47  std::lock_guard<std::mutex> lock(lock_);
48
49  epoll_event event;
50  event.events = event_mask;
51  event.data.ptr = &(handlers_[fd] = handler);
52
53  ALOGD_IF(
54      TRACE,
55      "EpollEventDispatcher::AddEventHandler: fd=%d event_mask=0x%x handler=%p",
56      fd, event_mask, event.data.ptr);
57
58  if (epoll_ctl(epoll_fd_.Get(), EPOLL_CTL_ADD, fd, &event) < 0) {
59    const int error = errno;
60    ALOGE("Failed to add fd to epoll set because: %s", strerror(error));
61    return pdx::ErrorStatus(error);
62  } else {
63    return {};
64  }
65}
66
67pdx::Status<void> EpollEventDispatcher::RemoveEventHandler(int fd) {
68  ALOGD_IF(TRACE, "EpollEventDispatcher::RemoveEventHandler: fd=%d", fd);
69  std::lock_guard<std::mutex> lock(lock_);
70
71  epoll_event dummy;  // See BUGS in man 2 epoll_ctl.
72  if (epoll_ctl(epoll_fd_.Get(), EPOLL_CTL_DEL, fd, &dummy) < 0) {
73    const int error = errno;
74    ALOGE("Failed to remove fd from epoll set because: %s", strerror(error));
75    return pdx::ErrorStatus(error);
76  }
77
78  // If the fd was valid above, add it to the list of ids to remove.
79  removed_handlers_.push_back(fd);
80
81  // Wake up the event thread to clean up.
82  eventfd_write(event_fd_.Get(), 1);
83
84  return {};
85}
86
87void EpollEventDispatcher::EventThread() {
88  prctl(PR_SET_NAME, reinterpret_cast<unsigned long>("VrEvent"), 0, 0, 0);
89
90  const int error = dvrSetSchedulerClass(0, "graphics");
91  LOG_ALWAYS_FATAL_IF(
92      error < 0,
93      "EpollEventDispatcher::EventThread: Failed to set scheduler class: %s",
94      strerror(-error));
95
96  const size_t kMaxNumEvents = 128;
97  epoll_event events[kMaxNumEvents];
98
99  while (!exit_thread_.load()) {
100    const int num_events = epoll_wait(epoll_fd_.Get(), events, kMaxNumEvents, -1);
101    if (num_events < 0 && errno != EINTR)
102      break;
103
104    ALOGD_IF(TRACE, "EpollEventDispatcher::EventThread: num_events=%d",
105             num_events);
106
107    for (int i = 0; i < num_events; i++) {
108      ALOGD_IF(
109          TRACE,
110          "EpollEventDispatcher::EventThread: event %d: handler=%p events=0x%x",
111          i, events[i].data.ptr, events[i].events);
112
113      if (events[i].data.ptr == this) {
114        // Clear pending event on event_fd_. Serialize the read with respect to
115        // writes from other threads.
116        std::lock_guard<std::mutex> lock(lock_);
117        eventfd_t value;
118        eventfd_read(event_fd_.Get(), &value);
119      } else {
120        auto handler = reinterpret_cast<Handler*>(events[i].data.ptr);
121        if (handler)
122          (*handler)(events[i].events);
123      }
124    }
125
126    // Remove any handlers that have been posted for removal. This is done here
127    // instead of in RemoveEventHandler() to prevent races between the dispatch
128    // thread and the code requesting the removal. Handlers are guaranteed to
129    // stay alive between exiting epoll_wait() and the dispatch loop above.
130    std::lock_guard<std::mutex> lock(lock_);
131    for (auto handler_fd : removed_handlers_) {
132      ALOGD_IF(TRACE,
133               "EpollEventDispatcher::EventThread: removing handler: fd=%d",
134               handler_fd);
135      handlers_.erase(handler_fd);
136    }
137    removed_handlers_.clear();
138  }
139}
140
141}  // namespace dvr
142}  // namespace android
143