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/osdep.h"
  14 #include "qemu-common.h"
  15 #include "qemu/event_notifier.h"
  16 #include "sysemu/char.h"
  17 #include "qemu/main-loop.h"
  18
  19 #ifdef CONFIG_EVENTFD
  20 #include <sys/eventfd.h>
  21 #endif
  22
  23 void event_notifier_init_fd(EventNotifier *e, int fd)
  24 {
  25     e->rfd = fd;
  26     e->wfd = fd;
  27 }
  28
  29 int event_notifier_init(EventNotifier *e, int active)
  30 {
  31     int fds[2];
  32     int ret;
  33
  34 #ifdef CONFIG_EVENTFD
  35     ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
  36 #else
  37     ret = -1;
  38     errno = ENOSYS;
  39 #endif
  40     if (ret >= 0) {
  41         e->rfd = e->wfd = ret;
  42     } else {
  43         if (errno != ENOSYS) {
  44             return -errno;
  45         }
  46         if (qemu_pipe(fds) < 0) {
  47             return -errno;
  48         }
  49         ret = fcntl_setfl(fds[0], O_NONBLOCK);
  50         if (ret < 0) {
  51             ret = -errno;
  52             goto fail;
  53         }
  54         ret = fcntl_setfl(fds[1], O_NONBLOCK);
  55         if (ret < 0) {
  56             ret = -errno;
  57             goto fail;
  58         }
  59         e->rfd = fds[0];
  60         e->wfd = fds[1];
  61     }
  62     if (active) {
  63         event_notifier_set(e);
  64     }
  65     return 0;
  66
  67 fail:
  68     close(fds[0]);
  69     close(fds[1]);
  70     return ret;
  71 }
  72
  73 void event_notifier_cleanup(EventNotifier *e)
  74 {
  75     if (e->rfd != e->wfd) {
  76         close(e->rfd);
  77     }
  78     close(e->wfd);
  79 }
  80
  81 int event_notifier_get_fd(const EventNotifier *e)
  82 {
  83     return e->rfd;
  84 }
  85
  86 int event_notifier_set_handler(EventNotifier *e,
  87                                EventNotifierHandler *handler)
  88 {
  89     qemu_set_fd_handler(e->rfd, (IOHandler *)handler, NULL, e);
  90     return 0;
  91 }
  92
  93 int event_notifier_set(EventNotifier *e)
  94 {
  95     static const uint64_t value = 1;
  96     ssize_t ret;
  97
  98     do {
  99         ret = write(e->wfd, &value, sizeof(value));
 100     } while (ret < 0 && errno == EINTR);
 101
 102     /* EAGAIN is fine, a read must be pending.  */
 103     if (ret < 0 && errno != EAGAIN) {
 104         return -errno;
 105     }
 106     return 0;
 107 }
 108
 109 int event_notifier_test_and_clear(EventNotifier *e)
 110 {
 111     int value;
 112     ssize_t len;
 113     char buffer[512];
 114
 115     /* Drain the notify pipe.  For eventfd, only 8 bytes will be read.  */
 116     value = 0;
 117     do {
 118         len = read(e->rfd, buffer, sizeof(buffer));
 119         value |= (len > 0);
 120     } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
 121
 122     return value;
 123 }