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/*
* 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 "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);
}
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