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/cutils.h"
  16 #include "qemu/event_notifier.h"
  17 #include "sysemu/char.h"
  18 #include "qemu/main-loop.h"
  19
  20 #ifdef CONFIG_EVENTFD
  21 #include <sys/eventfd.h>
  22 #endif
  23
  24 void event_notifier_init_fd(EventNotifier *e, int fd)
  25 {
  26     e->rfd = fd;
  27     e->wfd = fd;
  28 }
  29
  30 int event_notifier_init(EventNotifier *e, int active)
  31 {
  32     int fds[2];
  33     int ret;
  34
  35 #ifdef CONFIG_EVENTFD
  36     ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
  37 #else
  38     ret = -1;
  39     errno = ENOSYS;
  40 #endif
  41     if (ret >= 0) {
  42         e->rfd = e->wfd = ret;
  43     } else {
  44         if (errno != ENOSYS) {
  45             return -errno;
  46         }
  47         if (qemu_pipe(fds) < 0) {
  48             return -errno;
  49         }
  50         ret = fcntl_setfl(fds[0], O_NONBLOCK);
  51         if (ret < 0) {
  52             ret = -errno;
  53             goto fail;
  54         }
  55         ret = fcntl_setfl(fds[1], O_NONBLOCK);
  56         if (ret < 0) {
  57             ret = -errno;
  58             goto fail;
  59         }
  60         e->rfd = fds[0];
  61         e->wfd = fds[1];
  62     }
  63     if (active) {
  64         event_notifier_set(e);
  65     }
  66     return 0;
  67
  68 fail:
  69     close(fds[0]);
  70     close(fds[1]);
  71     return ret;
  72 }
  73
  74 void event_notifier_cleanup(EventNotifier *e)
  75 {
  76     if (e->rfd != e->wfd) {
  77         close(e->rfd);
  78     }
  79     close(e->wfd);
  80 }
  81
  82 int event_notifier_get_fd(const EventNotifier *e)
  83 {
  84     return e->rfd;
  85 }
  86
  87 int event_notifier_set_handler(EventNotifier *e,
  88                                EventNotifierHandler *handler)
  89 {
  90     qemu_set_fd_handler(e->rfd, (IOHandler *)handler, NULL, e);
  91     return 0;
  92 }
  93
  94 int event_notifier_set(EventNotifier *e)
  95 {
  96     static const uint64_t value = 1;
  97     ssize_t ret;
  98
  99     do {
 100         ret = write(e->wfd, &value, sizeof(value));
 101     } while (ret < 0 && errno == EINTR);
 102
 103     /* EAGAIN is fine, a read must be pending.  */
 104     if (ret < 0 && errno != EAGAIN) {
 105         return -errno;
 106     }
 107     return 0;
 108 }
 109
 110 int event_notifier_test_and_clear(EventNotifier *e)
 111 {
 112     int value;
 113     ssize_t len;
 114     char buffer[512];
 115
 116     /* Drain the notify pipe.  For eventfd, only 8 bytes will be read.  */
 117     value = 0;
 118     do {
 119         len = read(e->rfd, buffer, sizeof(buffer));
 120         value |= (len > 0);
 121     } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
 122
 123     return value;
 124 }