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Commit | Line | Data |
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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/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 | } | |
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 | e->rfd = -1; | |
84 | } | |
85 | close(e->wfd); | |
86 | e->wfd = -1; | |
87 | } | |
88 | ||
89 | int event_notifier_get_fd(const EventNotifier *e) | |
90 | { | |
91 | return e->rfd; | |
92 | } | |
93 | ||
94 | int 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 | ||
110 | int 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 | } |