aboutsummaryrefslogtreecommitdiff
path: root/util/event_notifier-posix.c
blob: 8307013c5df0788c93ba66ca8d43a3b498f4c32e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
/*
 * event notifier support
 *
 * Copyright Red Hat, Inc. 2010
 *
 * Authors:
 *  Michael S. Tsirkin <mst@redhat.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 */

#include "qemu/osdep.h"
#include "qemu-common.h"
#include "qemu/cutils.h"
#include "qemu/event_notifier.h"
#include "qemu/main-loop.h"

#ifdef CONFIG_EVENTFD
#include <sys/eventfd.h>
#endif

#ifdef CONFIG_EVENTFD
/*
 * Initialize @e with existing file descriptor @fd.
 * @fd must be a genuine eventfd object, emulation with pipe won't do.
 */
void event_notifier_init_fd(EventNotifier *e, int fd)
{
    e->rfd = fd;
    e->wfd = fd;
    e->initialized = true;
}
#endif

int event_notifier_init(EventNotifier *e, int active)
{
    int fds[2];
    int ret;

#ifdef CONFIG_EVENTFD
    ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
#else
    ret = -1;
    errno = ENOSYS;
#endif
    if (ret >= 0) {
        e->rfd = e->wfd = ret;
    } else {
        if (errno != ENOSYS) {
            return -errno;
        }
        if (qemu_pipe(fds) < 0) {
            return -errno;
        }
        ret = fcntl_setfl(fds[0], O_NONBLOCK);
        if (ret < 0) {
            ret = -errno;
            goto fail;
        }
        ret = fcntl_setfl(fds[1], O_NONBLOCK);
        if (ret < 0) {
            ret = -errno;
            goto fail;
        }
        e->rfd = fds[0];
        e->wfd = fds[1];
    }
    e->initialized = true;
    if (active) {
        event_notifier_set(e);
    }
    return 0;

fail:
    close(fds[0]);
    close(fds[1]);
    return ret;
}

void event_notifier_cleanup(EventNotifier *e)
{
    if (!e->initialized) {
        return;
    }

    if (e->rfd != e->wfd) {
        close(e->rfd);
    }

    e->rfd = -1;
    close(e->wfd);
    e->wfd = -1;
    e->initialized = false;
}

int event_notifier_get_fd(const EventNotifier *e)
{
    return e->rfd;
}

int event_notifier_set(EventNotifier *e)
{
    static const uint64_t value = 1;
    ssize_t ret;

    if (!e->initialized) {
        return -1;
    }

    do {
        ret = write(e->wfd, &value, sizeof(value));
    } while (ret < 0 && errno == EINTR);

    /* EAGAIN is fine, a read must be pending.  */
    if (ret < 0 && errno != EAGAIN) {
        return -errno;
    }
    return 0;
}

int event_notifier_test_and_clear(EventNotifier *e)
{
    int value;
    ssize_t len;
    char buffer[512];

    if (!e->initialized) {
        return 0;
    }

    /* Drain the notify pipe.  For eventfd, only 8 bytes will be read.  */
    value = 0;
    do {
        len = read(e->rfd, buffer, sizeof(buffer));
        value |= (len > 0);
    } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));

    return value;
}