/* * 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); }