/* * 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 or later. * See the COPYING file in the top-level directory. */ #include "qemu/osdep.h" #include "qemu-common.h" #include "qemu/cutils.h" #include "qemu/event_notifier.h" #include "qemu/main-loop.h" #ifdef CONFIG_EVENTFD #include <sys/eventfd.h> #endif #ifdef CONFIG_EVENTFD /* * Initialize @e with existing file descriptor @fd. * @fd must be a genuine eventfd object, emulation with pipe won't do. */ void event_notifier_init_fd(EventNotifier *e, int fd) { e->rfd = fd; e->wfd = fd; } #endif int event_notifier_init(EventNotifier *e, int active) { int fds[2]; int ret; #ifdef CONFIG_EVENTFD ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC); #else ret = -1; errno = ENOSYS; #endif if (ret >= 0) { e->rfd = e->wfd = ret; } else { if (errno != ENOSYS) { return -errno; } if (qemu_pipe(fds) < 0) { return -errno; } ret = fcntl_setfl(fds[0], O_NONBLOCK); if (ret < 0) { ret = -errno; goto fail; } ret = fcntl_setfl(fds[1], O_NONBLOCK); if (ret < 0) { ret = -errno; goto fail; } e->rfd = fds[0]; e->wfd = fds[1]; } if (active) { event_notifier_set(e); } return 0; fail: close(fds[0]); close(fds[1]); return ret; } void event_notifier_cleanup(EventNotifier *e) { if (e->rfd != e->wfd) { close(e->rfd); e->rfd = -1; } close(e->wfd); e->wfd = -1; } int event_notifier_get_fd(const EventNotifier *e) { return e->rfd; } int event_notifier_set(EventNotifier *e) { static const uint64_t value = 1; ssize_t ret; do { ret = write(e->wfd, &value, sizeof(value)); } while (ret < 0 && errno == EINTR); /* EAGAIN is fine, a read must be pending. */ if (ret < 0 && errno != EAGAIN) { return -errno; } return 0; } int event_notifier_test_and_clear(EventNotifier *e) { int value; ssize_t len; char buffer[512]; /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */ value = 0; do { len = read(e->rfd, buffer, sizeof(buffer)); value |= (len > 0); } while ((len == -1 && errno == EINTR) || len == sizeof(buffer)); return value; }