blob: 987bf94114957beca2250a221778f3f93c20d6d2 (
plain) (
blame)
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
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
/*
* linux/fs/fifo.c
*
* written by Paul H. Hargrove
*
* Fixes:
* 10-06-1999, AV: fixed OOM handling in fifo_open(), moved
* initialization there, switched to external
* allocation of pipe_inode_info.
*/
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/pipe_fs_i.h>
static void wait_for_partner(struct inode* inode, unsigned int *cnt)
{
int cur = *cnt;
while (cur == *cnt) {
pipe_wait(inode->i_pipe);
if (signal_pending(current))
break;
}
}
static void wake_up_partner(struct inode* inode)
{
wake_up_interruptible(&inode->i_pipe->wait);
}
static int fifo_open(struct inode *inode, struct file *filp)
{
struct pipe_inode_info *pipe;
int ret;
mutex_lock(&inode->i_mutex);
pipe = inode->i_pipe;
if (!pipe) {
ret = -ENOMEM;
pipe = alloc_pipe_info(inode);
if (!pipe)
goto err_nocleanup;
inode->i_pipe = pipe;
}
filp->f_version = 0;
/* We can only do regular read/write on fifos */
filp->f_mode &= (FMODE_READ | FMODE_WRITE);
switch (filp->f_mode) {
case 1:
/*
* O_RDONLY
* POSIX.1 says that O_NONBLOCK means return with the FIFO
* opened, even when there is no process writing the FIFO.
*/
filp->f_op = &read_pipefifo_fops;
pipe->r_counter++;
if (pipe->readers++ == 0)
wake_up_partner(inode);
if (!pipe->writers) {
if ((filp->f_flags & O_NONBLOCK)) {
/* suppress POLLHUP until we have
* seen a writer */
filp->f_version = pipe->w_counter;
} else
{
wait_for_partner(inode, &pipe->w_counter);
if(signal_pending(current))
goto err_rd;
}
}
break;
case 2:
/*
* O_WRONLY
* POSIX.1 says that O_NONBLOCK means return -1 with
* errno=ENXIO when there is no process reading the FIFO.
*/
ret = -ENXIO;
if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
goto err;
filp->f_op = &write_pipefifo_fops;
pipe->w_counter++;
if (!pipe->writers++)
wake_up_partner(inode);
if (!pipe->readers) {
wait_for_partner(inode, &pipe->r_counter);
if (signal_pending(current))
goto err_wr;
}
break;
case 3:
/*
* O_RDWR
* POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
* This implementation will NEVER block on a O_RDWR open, since
* the process can at least talk to itself.
*/
filp->f_op = &rdwr_pipefifo_fops;
pipe->readers++;
pipe->writers++;
pipe->r_counter++;
pipe->w_counter++;
if (pipe->readers == 1 || pipe->writers == 1)
wake_up_partner(inode);
break;
default:
ret = -EINVAL;
goto err;
}
/* Ok! */
mutex_unlock(&inode->i_mutex);
return 0;
err_rd:
if (!--pipe->readers)
wake_up_interruptible(&pipe->wait);
ret = -ERESTARTSYS;
goto err;
err_wr:
if (!--pipe->writers)
wake_up_interruptible(&pipe->wait);
ret = -ERESTARTSYS;
goto err;
err:
if (!pipe->readers && !pipe->writers)
free_pipe_info(inode);
err_nocleanup:
mutex_unlock(&inode->i_mutex);
return ret;
}
/*
* Dummy default file-operations: the only thing this does
* is contain the open that then fills in the correct operations
* depending on the access mode of the file...
*/
const struct file_operations def_fifo_fops = {
.open = fifo_open, /* will set read_ or write_pipefifo_fops */
};
|
