mirror of
https://gitlab.com/qemu-project/qemu
synced 2024-11-05 20:35:44 +00:00
2292b33986
event notifiers are slightly generalized eventfd descriptors. Current implementation depends on eventfd because vhost is the only user, and vhost depends on eventfd anyway, but a stub is provided for non-eventfd case. We'll be able to further generalize this when another user comes along and we see how to best do this. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
62 lines
1.3 KiB
C
62 lines
1.3 KiB
C
/*
|
|
* event notifier support
|
|
*
|
|
* Copyright Red Hat, Inc. 2010
|
|
*
|
|
* Authors:
|
|
* Michael S. Tsirkin <mst@redhat.com>
|
|
*
|
|
* This work is licensed under the terms of the GNU GPL, version 2. See
|
|
* the COPYING file in the top-level directory.
|
|
*/
|
|
|
|
#include "hw.h"
|
|
#include "event_notifier.h"
|
|
#ifdef CONFIG_EVENTFD
|
|
#include <sys/eventfd.h>
|
|
#endif
|
|
|
|
int event_notifier_init(EventNotifier *e, int active)
|
|
{
|
|
#ifdef CONFIG_EVENTFD
|
|
int fd = eventfd(!!active, EFD_NONBLOCK | EFD_CLOEXEC);
|
|
if (fd < 0)
|
|
return -errno;
|
|
e->fd = fd;
|
|
return 0;
|
|
#else
|
|
return -ENOSYS;
|
|
#endif
|
|
}
|
|
|
|
void event_notifier_cleanup(EventNotifier *e)
|
|
{
|
|
close(e->fd);
|
|
}
|
|
|
|
int event_notifier_get_fd(EventNotifier *e)
|
|
{
|
|
return e->fd;
|
|
}
|
|
|
|
int event_notifier_test_and_clear(EventNotifier *e)
|
|
{
|
|
uint64_t value;
|
|
int r = read(e->fd, &value, sizeof(value));
|
|
return r == sizeof(value);
|
|
}
|
|
|
|
int event_notifier_test(EventNotifier *e)
|
|
{
|
|
uint64_t value;
|
|
int r = read(e->fd, &value, sizeof(value));
|
|
if (r == sizeof(value)) {
|
|
/* restore previous value. */
|
|
int s = write(e->fd, &value, sizeof(value));
|
|
/* never blocks because we use EFD_SEMAPHORE.
|
|
* If we didn't we'd get EAGAIN on overflow
|
|
* and we'd have to write code to ignore it. */
|
|
assert(s == sizeof(value));
|
|
}
|
|
return r == sizeof(value);
|
|
}
|