aio: add AioPollFn and io_poll() interface
[qemu.git] / util / event_notifier-posix.c
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 "sysemu/char.h"
18 #include "qemu/main-loop.h"
19
20 #ifdef CONFIG_EVENTFD
21 #include <sys/eventfd.h>
22 #endif
23
24 #ifdef CONFIG_EVENTFD
25 /*
26 * Initialize @e with existing file descriptor @fd.
27 * @fd must be a genuine eventfd object, emulation with pipe won't do.
28 */
29 void event_notifier_init_fd(EventNotifier *e, int fd)
30 {
31 e->rfd = fd;
32 e->wfd = fd;
33 }
34 #endif
35
36 int event_notifier_init(EventNotifier *e, int active)
37 {
38 int fds[2];
39 int ret;
40
41 #ifdef CONFIG_EVENTFD
42 ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
43 #else
44 ret = -1;
45 errno = ENOSYS;
46 #endif
47 if (ret >= 0) {
48 e->rfd = e->wfd = ret;
49 } else {
50 if (errno != ENOSYS) {
51 return -errno;
52 }
53 if (qemu_pipe(fds) < 0) {
54 return -errno;
55 }
56 ret = fcntl_setfl(fds[0], O_NONBLOCK);
57 if (ret < 0) {
58 ret = -errno;
59 goto fail;
60 }
61 ret = fcntl_setfl(fds[1], O_NONBLOCK);
62 if (ret < 0) {
63 ret = -errno;
64 goto fail;
65 }
66 e->rfd = fds[0];
67 e->wfd = fds[1];
68 }
69 if (active) {
70 event_notifier_set(e);
71 }
72 return 0;
73
74 fail:
75 close(fds[0]);
76 close(fds[1]);
77 return ret;
78 }
79
80 void event_notifier_cleanup(EventNotifier *e)
81 {
82 if (e->rfd != e->wfd) {
83 close(e->rfd);
84 }
85 close(e->wfd);
86 }
87
88 int event_notifier_get_fd(const EventNotifier *e)
89 {
90 return e->rfd;
91 }
92
93 int event_notifier_set_handler(EventNotifier *e,
94 bool is_external,
95 EventNotifierHandler *handler)
96 {
97 aio_set_fd_handler(iohandler_get_aio_context(), e->rfd, is_external,
98 (IOHandler *)handler, NULL, NULL, e);
99 return 0;
100 }
101
102 int event_notifier_set(EventNotifier *e)
103 {
104 static const uint64_t value = 1;
105 ssize_t ret;
106
107 do {
108 ret = write(e->wfd, &value, sizeof(value));
109 } while (ret < 0 && errno == EINTR);
110
111 /* EAGAIN is fine, a read must be pending. */
112 if (ret < 0 && errno != EAGAIN) {
113 return -errno;
114 }
115 return 0;
116 }
117
118 int event_notifier_test_and_clear(EventNotifier *e)
119 {
120 int value;
121 ssize_t len;
122 char buffer[512];
123
124 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */
125 value = 0;
126 do {
127 len = read(e->rfd, buffer, sizeof(buffer));
128 value |= (len > 0);
129 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
130
131 return value;
132 }