util/event_notifier-posix.c

   1 /*
   2  * event notifier support
   3  *
   4  * Copyright Red Hat, Inc. 2010
   5  *
   6  * Authors:
   7  *  Michael S. Tsirkin <mst@redhat.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  */
  12
  13 #include "qemu-common.h"
  14 #include "qemu/event_notifier.h"
  15 #include "sysemu/char.h"
  16 #include "qemu/main-loop.h"
  17
  18 #ifdef CONFIG_EVENTFD
  19 #include <sys/eventfd.h>
  20 #endif
  21
  22 void event_notifier_init_fd(EventNotifier *e, int fd)
  23 {
  24     e->rfd = fd;
  25     e->wfd = fd;
  26 }
  27
  28 int event_notifier_init(EventNotifier *e, int active)
  29 {
  30     int fds[2];
  31     int ret;
  32
  33 #ifdef CONFIG_EVENTFD
  34     ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
  35 #else
  36     ret = -1;
  37     errno = ENOSYS;
  38 #endif
  39     if (ret >= 0) {
  40         e->rfd = e->wfd = ret;
  41     } else {
  42         if (errno != ENOSYS) {
  43             return -errno;
  44         }
  45         if (qemu_pipe(fds) < 0) {
  46             return -errno;
  47         }
  48         ret = fcntl_setfl(fds[0], O_NONBLOCK);
  49         if (ret < 0) {
  50             ret = -errno;
  51             goto fail;
  52         }
  53         ret = fcntl_setfl(fds[1], O_NONBLOCK);
  54         if (ret < 0) {
  55             ret = -errno;
  56             goto fail;
  57         }
  58         e->rfd = fds[0];
  59         e->wfd = fds[1];
  60     }
  61     if (active) {
  62         event_notifier_set(e);
  63     }
  64     return 0;
  65
  66 fail:
  67     close(fds[0]);
  68     close(fds[1]);
  69     return ret;
  70 }
  71
  72 void event_notifier_cleanup(EventNotifier *e)
  73 {
  74     if (e->rfd != e->wfd) {
  75         close(e->rfd);
  76     }
  77     close(e->wfd);
  78 }
  79
  80 int event_notifier_get_fd(EventNotifier *e)
  81 {
  82     return e->rfd;
  83 }
  84
  85 int event_notifier_set_handler(EventNotifier *e,
  86                                EventNotifierHandler *handler)
  87 {
  88     qemu_set_fd_handler(e->rfd, (IOHandler *)handler, NULL, e);
  89     return 0;
  90 }
  91
  92 int event_notifier_set(EventNotifier *e)
  93 {
  94     static const uint64_t value = 1;
  95     ssize_t ret;
  96
  97     do {
  98         ret = write(e->wfd, &value, sizeof(value));
  99     } while (ret < 0 && errno == EINTR);
 100
 101     /* EAGAIN is fine, a read must be pending.  */
 102     if (ret < 0 && errno != EAGAIN) {
 103         return -errno;
 104     }
 105     return 0;
 106 }
 107
 108 int event_notifier_test_and_clear(EventNotifier *e)
 109 {
 110     int value;
 111     ssize_t len;
 112     char buffer[512];
 113
 114     /* Drain the notify pipe.  For eventfd, only 8 bytes will be read.  */
 115     value = 0;
 116     do {
 117         len = read(e->rfd, buffer, sizeof(buffer));
 118         value |= (len > 0);
 119     } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
 120
 121     return value;
 122 }