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#include "epoll_event_dispatcher.h"
#include <log/log.h>
#include <sys/epoll.h>
#include <sys/eventfd.h>
#include <sys/prctl.h>
#include <dvr/performance_client_api.h>
namespace android {
namespace dvr {
EpollEventDispatcher::EpollEventDispatcher() {
epoll_fd_.Reset(epoll_create1(EPOLL_CLOEXEC));
if (!epoll_fd_) {
ALOGE("Failed to create epoll fd: %s", strerror(errno));
return;
}
event_fd_.Reset(eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK));
if (!event_fd_) {
ALOGE("Failed to create event for epolling: %s", strerror(errno));
return;
}
// Add watch for eventfd. This should only watch for EPOLLIN, which gets set
// when eventfd_write occurs. Use "this" as a unique sentinal value to
// identify events from the event fd.
epoll_event event = {.events = EPOLLIN, .data = {.ptr = this}};
if (epoll_ctl(epoll_fd_.Get(), EPOLL_CTL_ADD, event_fd_.Get(), &event) < 0) {
ALOGE("Failed to add eventfd to epoll set because: %s", strerror(errno));
return;
}
thread_ = std::thread(&EpollEventDispatcher::EventThread, this);
}
EpollEventDispatcher::~EpollEventDispatcher() { Stop(); }
void EpollEventDispatcher::Stop() {
exit_thread_.store(true);
eventfd_write(event_fd_.Get(), 1);
}
pdx::Status<void> EpollEventDispatcher::AddEventHandler(int fd, int event_mask,
Handler handler) {
std::lock_guard<std::mutex> lock(lock_);
epoll_event event;
event.events = event_mask;
event.data.ptr = &(handlers_[fd] = handler);
ALOGD_IF(
TRACE,
"EpollEventDispatcher::AddEventHandler: fd=%d event_mask=0x%x handler=%p",
fd, event_mask, event.data.ptr);
if (epoll_ctl(epoll_fd_.Get(), EPOLL_CTL_ADD, fd, &event) < 0) {
const int error = errno;
ALOGE("Failed to add fd to epoll set because: %s", strerror(error));
return pdx::ErrorStatus(error);
} else {
return {};
}
}
pdx::Status<void> EpollEventDispatcher::RemoveEventHandler(int fd) {
ALOGD_IF(TRACE, "EpollEventDispatcher::RemoveEventHandler: fd=%d", fd);
std::lock_guard<std::mutex> lock(lock_);
epoll_event dummy; // See BUGS in man 2 epoll_ctl.
if (epoll_ctl(epoll_fd_.Get(), EPOLL_CTL_DEL, fd, &dummy) < 0) {
const int error = errno;
ALOGE("Failed to remove fd from epoll set because: %s", strerror(error));
return pdx::ErrorStatus(error);
}
// If the fd was valid above, add it to the list of ids to remove.
removed_handlers_.push_back(fd);
// Wake up the event thread to clean up.
eventfd_write(event_fd_.Get(), 1);
return {};
}
void EpollEventDispatcher::EventThread() {
prctl(PR_SET_NAME, reinterpret_cast<unsigned long>("VrEvent"), 0, 0, 0);
const int error = dvrSetSchedulerClass(0, "graphics");
LOG_ALWAYS_FATAL_IF(
error < 0,
"EpollEventDispatcher::EventThread: Failed to set scheduler class: %s",
strerror(-error));
const size_t kMaxNumEvents = 128;
epoll_event events[kMaxNumEvents];
while (!exit_thread_.load()) {
const int num_events = epoll_wait(epoll_fd_.Get(), events, kMaxNumEvents, -1);
if (num_events < 0 && errno != EINTR)
break;
ALOGD_IF(TRACE > 1, "EpollEventDispatcher::EventThread: num_events=%d",
num_events);
for (int i = 0; i < num_events; i++) {
ALOGD_IF(
TRACE > 1,
"EpollEventDispatcher::EventThread: event %d: handler=%p events=0x%x",
i, events[i].data.ptr, events[i].events);
if (events[i].data.ptr == this) {
// Clear pending event on event_fd_. Serialize the read with respect to
// writes from other threads.
std::lock_guard<std::mutex> lock(lock_);
eventfd_t value;
eventfd_read(event_fd_.Get(), &value);
} else {
auto handler = reinterpret_cast<Handler*>(events[i].data.ptr);
if (handler)
(*handler)(events[i].events);
}
}
// Remove any handlers that have been posted for removal. This is done here
// instead of in RemoveEventHandler() to prevent races between the dispatch
// thread and the code requesting the removal. Handlers are guaranteed to
// stay alive between exiting epoll_wait() and the dispatch loop above.
std::lock_guard<std::mutex> lock(lock_);
for (auto handler_fd : removed_handlers_) {
ALOGD_IF(TRACE,
"EpollEventDispatcher::EventThread: removing handler: fd=%d",
handler_fd);
handlers_.erase(handler_fd);
}
removed_handlers_.clear();
}
}
} // namespace dvr
} // namespace android
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