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 "qemu/main-loop.h"
18
19#ifdef CONFIG_EVENTFD
20#include <sys/eventfd.h>
21#endif
22
23#ifdef CONFIG_EVENTFD
24/*
25 * Initialize @e with existing file descriptor @fd.
26 * @fd must be a genuine eventfd object, emulation with pipe won't do.
27 */
28void event_notifier_init_fd(EventNotifier *e, int fd)
29{
30 e->rfd = fd;
31 e->wfd = fd;
32}
33#endif
34
35int event_notifier_init(EventNotifier *e, int active)
36{
37 int fds[2];
38 int ret;
39
40#ifdef CONFIG_EVENTFD
41 ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
42#else
43 ret = -1;
44 errno = ENOSYS;
45#endif
46 if (ret >= 0) {
47 e->rfd = e->wfd = ret;
48 } else {
49 if (errno != ENOSYS) {
50 return -errno;
51 }
52 if (qemu_pipe(fds) < 0) {
53 return -errno;
54 }
55 ret = fcntl_setfl(fds[0], O_NONBLOCK);
56 if (ret < 0) {
57 ret = -errno;
58 goto fail;
59 }
60 ret = fcntl_setfl(fds[1], O_NONBLOCK);
61 if (ret < 0) {
62 ret = -errno;
63 goto fail;
64 }
65 e->rfd = fds[0];
66 e->wfd = fds[1];
67 }
68 if (active) {
69 event_notifier_set(e);
70 }
71 return 0;
72
73fail:
74 close(fds[0]);
75 close(fds[1]);
76 return ret;
77}
78
79void event_notifier_cleanup(EventNotifier *e)
80{
81 if (e->rfd != e->wfd) {
82 close(e->rfd);
83 e->rfd = -1;
84 }
85 close(e->wfd);
86 e->wfd = -1;
87}
88
89int event_notifier_get_fd(const EventNotifier *e)
90{
91 return e->rfd;
92}
93
94int 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
110int 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}
125