4 * written by Paul H. Hargrove
7 * 10-06-1999, AV: fixed OOM handling in fifo_open(), moved
8 * initialization there, switched to external
9 * allocation of pipe_inode_info.
13 #include <linux/slab.h>
14 #include <linux/smp_lock.h>
16 #include <linux/pipe_fs_i.h>
18 static void wait_for_partner(struct inode* inode, unsigned int *cnt)
23 pipe_wait(inode->i_pipe);
24 if (signal_pending(current))
29 static void wake_up_partner(struct inode* inode)
31 wake_up_interruptible(PIPE_WAIT(*inode));
34 static int fifo_open(struct inode *inode, struct file *filp)
38 mutex_lock(PIPE_MUTEX(*inode));
41 inode->i_pipe = alloc_pipe_info(inode);
47 /* We can only do regular read/write on fifos */
48 filp->f_mode &= (FMODE_READ | FMODE_WRITE);
50 switch (filp->f_mode) {
54 * POSIX.1 says that O_NONBLOCK means return with the FIFO
55 * opened, even when there is no process writing the FIFO.
57 filp->f_op = &read_fifo_fops;
58 PIPE_RCOUNTER(*inode)++;
59 if (PIPE_READERS(*inode)++ == 0)
60 wake_up_partner(inode);
62 if (!PIPE_WRITERS(*inode)) {
63 if ((filp->f_flags & O_NONBLOCK)) {
64 /* suppress POLLHUP until we have
66 filp->f_version = PIPE_WCOUNTER(*inode);
69 wait_for_partner(inode, &PIPE_WCOUNTER(*inode));
70 if(signal_pending(current))
79 * POSIX.1 says that O_NONBLOCK means return -1 with
80 * errno=ENXIO when there is no process reading the FIFO.
83 if ((filp->f_flags & O_NONBLOCK) && !PIPE_READERS(*inode))
86 filp->f_op = &write_fifo_fops;
87 PIPE_WCOUNTER(*inode)++;
88 if (!PIPE_WRITERS(*inode)++)
89 wake_up_partner(inode);
91 if (!PIPE_READERS(*inode)) {
92 wait_for_partner(inode, &PIPE_RCOUNTER(*inode));
93 if (signal_pending(current))
101 * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
102 * This implementation will NEVER block on a O_RDWR open, since
103 * the process can at least talk to itself.
105 filp->f_op = &rdwr_fifo_fops;
107 PIPE_READERS(*inode)++;
108 PIPE_WRITERS(*inode)++;
109 PIPE_RCOUNTER(*inode)++;
110 PIPE_WCOUNTER(*inode)++;
111 if (PIPE_READERS(*inode) == 1 || PIPE_WRITERS(*inode) == 1)
112 wake_up_partner(inode);
121 mutex_unlock(PIPE_MUTEX(*inode));
125 if (!--PIPE_READERS(*inode))
126 wake_up_interruptible(PIPE_WAIT(*inode));
131 if (!--PIPE_WRITERS(*inode))
132 wake_up_interruptible(PIPE_WAIT(*inode));
137 if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode))
138 free_pipe_info(inode);
141 mutex_unlock(PIPE_MUTEX(*inode));
146 * Dummy default file-operations: the only thing this does
147 * is contain the open that then fills in the correct operations
148 * depending on the access mode of the file...
150 const struct file_operations def_fifo_fops = {
151 .open = fifo_open, /* will set read or write pipe_fops */