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/cutils.h"
  15 #include "qemu/event_notifier.h"
  16 #include "qemu/main-loop.h"
  17
  18 #ifdef CONFIG_EVENTFD
  19 #include <sys/eventfd.h>
  20 #endif
  21
  22 #ifdef CONFIG_EVENTFD
  23 /*
  24  * Initialize @e with existing file descriptor @fd.
  25  * @fd must be a genuine eventfd object, emulation with pipe won't do.
  26  */
  27 void event_notifier_init_fd(EventNotifier *e, int fd)
  28 {
  29     e->rfd = fd;
  30     e->wfd = fd;
  31     e->initialized = true;
  32 }
  33 #endif
  34
  35 int event_notifier_init(EventNotifier *e, int active)
  36 {
  37     int fds[2];
  38     int ret;
  39
  40 #ifdef CONFIG_EVENTFD
  41     ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
  42 #else
  43     ret = -1;
  44     errno = ENOSYS;
  45 #endif
  46     if (ret >= 0) {
  47         e->rfd = e->wfd = ret;
  48     } else {
  49         if (errno != ENOSYS) {
  50             return -errno;
  51         }
  52         if (qemu_pipe(fds) < 0) {
  53             return -errno;
  54         }
  55         ret = fcntl_setfl(fds[0], O_NONBLOCK);
  56         if (ret < 0) {
  57             ret = -errno;
  58             goto fail;
  59         }
  60         ret = fcntl_setfl(fds[1], O_NONBLOCK);
  61         if (ret < 0) {
  62             ret = -errno;
  63             goto fail;
  64         }
  65         e->rfd = fds[0];
  66         e->wfd = fds[1];
  67     }
  68     e->initialized = true;
  69     if (active) {
  70         event_notifier_set(e);
  71     }
  72     return 0;
  73
  74 fail:
  75     close(fds[0]);
  76     close(fds[1]);
  77     return ret;
  78 }
  79
  80 void event_notifier_cleanup(EventNotifier *e)
  81 {
  82     if (!e->initialized) {
  83         return;
  84     }
  85
  86     if (e->rfd != e->wfd) {
  87         close(e->rfd);
  88     }
  89
  90     e->rfd = -1;
  91     close(e->wfd);
  92     e->wfd = -1;
  93     e->initialized = false;
  94 }
  95
  96 int event_notifier_get_fd(const EventNotifier *e)
  97 {
  98     return e->rfd;
  99 }
 100
 101 int event_notifier_get_wfd(const EventNotifier *e)
 102 {
 103     return e->wfd;
 104 }
 105
 106 int event_notifier_set(EventNotifier *e)
 107 {
 108     static const uint64_t value = 1;
 109     ssize_t ret;
 110
 111     if (!e->initialized) {
 112         return -1;
 113     }
 114
 115     do {
 116         ret = write(e->wfd, &value, sizeof(value));
 117     } while (ret < 0 && errno == EINTR);
 118
 119     /* EAGAIN is fine, a read must be pending.  */
 120     if (ret < 0 && errno != EAGAIN) {
 121         return -errno;
 122     }
 123     return 0;
 124 }
 125
 126 int event_notifier_test_and_clear(EventNotifier *e)
 127 {
 128     int value;
 129     ssize_t len;
 130     char buffer[512];
 131
 132     if (!e->initialized) {
 133         return 0;
 134     }
 135
 136     /* Drain the notify pipe.  For eventfd, only 8 bytes will be read.  */
 137     value = 0;
 138     do {
 139         len = read(e->rfd, buffer, sizeof(buffer));
 140         value |= (len > 0);
 141     } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
 142
 143     return value;
 144 }