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