Root/
1 | /* |
2 | * linux/fs/fifo.c |
3 | * |
4 | * written by Paul H. Hargrove |
5 | * |
6 | * Fixes: |
7 | * 10-06-1999, AV: fixed OOM handling in fifo_open(), moved |
8 | * initialization there, switched to external |
9 | * allocation of pipe_inode_info. |
10 | */ |
11 | |
12 | #include <linux/mm.h> |
13 | #include <linux/slab.h> |
14 | #include <linux/fs.h> |
15 | #include <linux/sched.h> |
16 | #include <linux/pipe_fs_i.h> |
17 | |
18 | static void wait_for_partner(struct inode* inode, unsigned int *cnt) |
19 | { |
20 | int cur = *cnt; |
21 | |
22 | while (cur == *cnt) { |
23 | pipe_wait(inode->i_pipe); |
24 | if (signal_pending(current)) |
25 | break; |
26 | } |
27 | } |
28 | |
29 | static void wake_up_partner(struct inode* inode) |
30 | { |
31 | wake_up_interruptible(&inode->i_pipe->wait); |
32 | } |
33 | |
34 | static int fifo_open(struct inode *inode, struct file *filp) |
35 | { |
36 | struct pipe_inode_info *pipe; |
37 | int ret; |
38 | |
39 | mutex_lock(&inode->i_mutex); |
40 | pipe = inode->i_pipe; |
41 | if (!pipe) { |
42 | ret = -ENOMEM; |
43 | pipe = alloc_pipe_info(inode); |
44 | if (!pipe) |
45 | goto err_nocleanup; |
46 | inode->i_pipe = pipe; |
47 | } |
48 | filp->f_version = 0; |
49 | |
50 | /* We can only do regular read/write on fifos */ |
51 | filp->f_mode &= (FMODE_READ | FMODE_WRITE); |
52 | |
53 | switch (filp->f_mode) { |
54 | case FMODE_READ: |
55 | /* |
56 | * O_RDONLY |
57 | * POSIX.1 says that O_NONBLOCK means return with the FIFO |
58 | * opened, even when there is no process writing the FIFO. |
59 | */ |
60 | filp->f_op = &read_pipefifo_fops; |
61 | pipe->r_counter++; |
62 | if (pipe->readers++ == 0) |
63 | wake_up_partner(inode); |
64 | |
65 | if (!pipe->writers) { |
66 | if ((filp->f_flags & O_NONBLOCK)) { |
67 | /* suppress POLLHUP until we have |
68 | * seen a writer */ |
69 | filp->f_version = pipe->w_counter; |
70 | } else |
71 | { |
72 | wait_for_partner(inode, &pipe->w_counter); |
73 | if(signal_pending(current)) |
74 | goto err_rd; |
75 | } |
76 | } |
77 | break; |
78 | |
79 | case FMODE_WRITE: |
80 | /* |
81 | * O_WRONLY |
82 | * POSIX.1 says that O_NONBLOCK means return -1 with |
83 | * errno=ENXIO when there is no process reading the FIFO. |
84 | */ |
85 | ret = -ENXIO; |
86 | if ((filp->f_flags & O_NONBLOCK) && !pipe->readers) |
87 | goto err; |
88 | |
89 | filp->f_op = &write_pipefifo_fops; |
90 | pipe->w_counter++; |
91 | if (!pipe->writers++) |
92 | wake_up_partner(inode); |
93 | |
94 | if (!pipe->readers) { |
95 | wait_for_partner(inode, &pipe->r_counter); |
96 | if (signal_pending(current)) |
97 | goto err_wr; |
98 | } |
99 | break; |
100 | |
101 | case FMODE_READ | FMODE_WRITE: |
102 | /* |
103 | * O_RDWR |
104 | * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set. |
105 | * This implementation will NEVER block on a O_RDWR open, since |
106 | * the process can at least talk to itself. |
107 | */ |
108 | filp->f_op = &rdwr_pipefifo_fops; |
109 | |
110 | pipe->readers++; |
111 | pipe->writers++; |
112 | pipe->r_counter++; |
113 | pipe->w_counter++; |
114 | if (pipe->readers == 1 || pipe->writers == 1) |
115 | wake_up_partner(inode); |
116 | break; |
117 | |
118 | default: |
119 | ret = -EINVAL; |
120 | goto err; |
121 | } |
122 | |
123 | /* Ok! */ |
124 | mutex_unlock(&inode->i_mutex); |
125 | return 0; |
126 | |
127 | err_rd: |
128 | if (!--pipe->readers) |
129 | wake_up_interruptible(&pipe->wait); |
130 | ret = -ERESTARTSYS; |
131 | goto err; |
132 | |
133 | err_wr: |
134 | if (!--pipe->writers) |
135 | wake_up_interruptible(&pipe->wait); |
136 | ret = -ERESTARTSYS; |
137 | goto err; |
138 | |
139 | err: |
140 | if (!pipe->readers && !pipe->writers) |
141 | free_pipe_info(inode); |
142 | |
143 | err_nocleanup: |
144 | mutex_unlock(&inode->i_mutex); |
145 | return ret; |
146 | } |
147 | |
148 | /* |
149 | * Dummy default file-operations: the only thing this does |
150 | * is contain the open that then fills in the correct operations |
151 | * depending on the access mode of the file... |
152 | */ |
153 | const struct file_operations def_fifo_fops = { |
154 | .open = fifo_open, /* will set read_ or write_pipefifo_fops */ |
155 | }; |
156 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9