hw/dataplane/event-poll.c

   1 /*
   2  * Event loop with file descriptor polling
   3  *
   4  * Copyright 2012 IBM, Corp.
   5  * Copyright 2012 Red Hat, Inc. and/or its affiliates
   6  *
   7  * Authors:
   8  *   Stefan Hajnoczi <stefanha@redhat.com>
   9  *
  10  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  11  * See the COPYING file in the top-level directory.
  12  *
  13  */
  14
  15 #include <sys/epoll.h>
  16 #include "hw/dataplane/event-poll.h"
  17
  18 /* Add an event notifier and its callback for polling */
  19 void event_poll_add(EventPoll *poll, EventHandler *handler,
  20                     EventNotifier *notifier, EventCallback *callback)
  21 {
  22     struct epoll_event event = {
  23         .events = EPOLLIN,
  24         .data.ptr = handler,
  25     };
  26     handler->notifier = notifier;
  27     handler->callback = callback;
  28     if (epoll_ctl(poll->epoll_fd, EPOLL_CTL_ADD,
  29                   event_notifier_get_fd(notifier), &event) != 0) {
  30         fprintf(stderr, "failed to add event handler to epoll: %m\n");
  31         exit(1);
  32     }
  33 }
  34
  35 /* Event callback for stopping event_poll() */
  36 static void handle_stop(EventHandler *handler)
  37 {
  38     /* Do nothing */
  39 }
  40
  41 void event_poll_init(EventPoll *poll)
  42 {
  43     /* Create epoll file descriptor */
  44     poll->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
  45     if (poll->epoll_fd < 0) {
  46         fprintf(stderr, "epoll_create1 failed: %m\n");
  47         exit(1);
  48     }
  49
  50     /* Set up stop notifier */
  51     if (event_notifier_init(&poll->stop_notifier, 0) < 0) {
  52         fprintf(stderr, "failed to init stop notifier\n");
  53         exit(1);
  54     }
  55     event_poll_add(poll, &poll->stop_handler,
  56                    &poll->stop_notifier, handle_stop);
  57 }
  58
  59 void event_poll_cleanup(EventPoll *poll)
  60 {
  61     event_notifier_cleanup(&poll->stop_notifier);
  62     close(poll->epoll_fd);
  63     poll->epoll_fd = -1;
  64 }
  65
  66 /* Block until the next event and invoke its callback */
  67 void event_poll(EventPoll *poll)
  68 {
  69     EventHandler *handler;
  70     struct epoll_event event;
  71     int nevents;
  72
  73     /* Wait for the next event.  Only do one event per call to keep the
  74      * function simple, this could be changed later. */
  75     do {
  76         nevents = epoll_wait(poll->epoll_fd, &event, 1, -1);
  77     } while (nevents < 0 && errno == EINTR);
  78     if (unlikely(nevents != 1)) {
  79         fprintf(stderr, "epoll_wait failed: %m\n");
  80         exit(1); /* should never happen */
  81     }
  82
  83     /* Find out which event handler has become active */
  84     handler = event.data.ptr;
  85
  86     /* Clear the eventfd */
  87     event_notifier_test_and_clear(handler->notifier);
  88
  89     /* Handle the event */
  90     handler->callback(handler);
  91 }
  92
  93 /* Stop event_poll()
  94  *
  95  * This function can be used from another thread.
  96  */
  97 void event_poll_notify(EventPoll *poll)
  98 {
  99     event_notifier_set(&poll->stop_notifier);
 100 }