Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20210921' into staging
[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 "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 e->initialized = true;
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 e->initialized = true;
70 if (active) {
71 event_notifier_set(e);
72 }
73 return 0;
74
75 fail:
76 close(fds[0]);
77 close(fds[1]);
78 return ret;
79 }
80
81 void event_notifier_cleanup(EventNotifier *e)
82 {
83 if (!e->initialized) {
84 return;
85 }
86
87 if (e->rfd != e->wfd) {
88 close(e->rfd);
89 }
90
91 e->rfd = -1;
92 close(e->wfd);
93 e->wfd = -1;
94 e->initialized = false;
95 }
96
97 int event_notifier_get_fd(const EventNotifier *e)
98 {
99 return e->rfd;
100 }
101
102 int event_notifier_set(EventNotifier *e)
103 {
104 static const uint64_t value = 1;
105 ssize_t ret;
106
107 if (!e->initialized) {
108 return -1;
109 }
110
111 do {
112 ret = write(e->wfd, &value, sizeof(value));
113 } while (ret < 0 && errno == EINTR);
114
115 /* EAGAIN is fine, a read must be pending. */
116 if (ret < 0 && errno != EAGAIN) {
117 return -errno;
118 }
119 return 0;
120 }
121
122 int event_notifier_test_and_clear(EventNotifier *e)
123 {
124 int value;
125 ssize_t len;
126 char buffer[512];
127
128 if (!e->initialized) {
129 return 0;
130 }
131
132 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */
133 value = 0;
134 do {
135 len = read(e->rfd, buffer, sizeof(buffer));
136 value |= (len > 0);
137 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
138
139 return value;
140 }