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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/event_notifier.h"
16 #include "sysemu/char.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 */
28 void event_notifier_init_fd(EventNotifier *e, int fd)
29 {
30 e->rfd = fd;
31 e->wfd = fd;
32 }
33 #endif
34
35 int 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
73 fail:
74 close(fds[0]);
75 close(fds[1]);
76 return ret;
77 }
78
79 void event_notifier_cleanup(EventNotifier *e)
80 {
81 if (e->rfd != e->wfd) {
82 close(e->rfd);
83 }
84 close(e->wfd);
85 }
86
87 int event_notifier_get_fd(const EventNotifier *e)
88 {
89 return e->rfd;
90 }
91
92 int event_notifier_set_handler(EventNotifier *e,
93 EventNotifierHandler *handler)
94 {
95 qemu_set_fd_handler(e->rfd, (IOHandler *)handler, NULL, e);
96 return 0;
97 }
98
99 int event_notifier_set(EventNotifier *e)
100 {
101 static const uint64_t value = 1;
102 ssize_t ret;
103
104 do {
105 ret = write(e->wfd, &value, sizeof(value));
106 } while (ret < 0 && errno == EINTR);
107
108 /* EAGAIN is fine, a read must be pending. */
109 if (ret < 0 && errno != EAGAIN) {
110 return -errno;
111 }
112 return 0;
113 }
114
115 int event_notifier_test_and_clear(EventNotifier *e)
116 {
117 int value;
118 ssize_t len;
119 char buffer[512];
120
121 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */
122 value = 0;
123 do {
124 len = read(e->rfd, buffer, sizeof(buffer));
125 value |= (len > 0);
126 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
127
128 return value;
129 }