Merge tag 'edgar/xilinx-next-2022-09-21.for-upstream' of https://github.com/edgarigl...
[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/cutils.h"
15 #include "qemu/event_notifier.h"
16 #include "qemu/main-loop.h"
17
18 #ifdef CONFIG_EVENTFD
19 #include <sys/eventfd.h>
20 #endif
21
22 #ifdef CONFIG_EVENTFD
23 /*
24 * Initialize @e with existing file descriptor @fd.
25 * @fd must be a genuine eventfd object, emulation with pipe won't do.
26 */
27 void event_notifier_init_fd(EventNotifier *e, int fd)
28 {
29 e->rfd = fd;
30 e->wfd = fd;
31 e->initialized = true;
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 (!g_unix_open_pipe(fds, FD_CLOEXEC, NULL)) {
53 return -errno;
54 }
55 if (!g_unix_set_fd_nonblocking(fds[0], true, NULL)) {
56 ret = -errno;
57 goto fail;
58 }
59 if (!g_unix_set_fd_nonblocking(fds[1], true, NULL)) {
60 ret = -errno;
61 goto fail;
62 }
63 e->rfd = fds[0];
64 e->wfd = fds[1];
65 }
66 e->initialized = true;
67 if (active) {
68 event_notifier_set(e);
69 }
70 return 0;
71
72 fail:
73 close(fds[0]);
74 close(fds[1]);
75 return ret;
76 }
77
78 void event_notifier_cleanup(EventNotifier *e)
79 {
80 if (!e->initialized) {
81 return;
82 }
83
84 if (e->rfd != e->wfd) {
85 close(e->rfd);
86 }
87
88 e->rfd = -1;
89 close(e->wfd);
90 e->wfd = -1;
91 e->initialized = false;
92 }
93
94 int event_notifier_get_fd(const EventNotifier *e)
95 {
96 return e->rfd;
97 }
98
99 int event_notifier_get_wfd(const EventNotifier *e)
100 {
101 return e->wfd;
102 }
103
104 int event_notifier_set(EventNotifier *e)
105 {
106 static const uint64_t value = 1;
107 ssize_t ret;
108
109 if (!e->initialized) {
110 return -1;
111 }
112
113 do {
114 ret = write(e->wfd, &value, sizeof(value));
115 } while (ret < 0 && errno == EINTR);
116
117 /* EAGAIN is fine, a read must be pending. */
118 if (ret < 0 && errno != EAGAIN) {
119 return -errno;
120 }
121 return 0;
122 }
123
124 int event_notifier_test_and_clear(EventNotifier *e)
125 {
126 int value;
127 ssize_t len;
128 char buffer[512];
129
130 if (!e->initialized) {
131 return 0;
132 }
133
134 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */
135 value = 0;
136 do {
137 len = read(e->rfd, buffer, sizeof(buffer));
138 value |= (len > 0);
139 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
140
141 return value;
142 }