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(&inode->i_pipe->wait);
34 static int fifo_open(struct inode *inode, struct file *filp)
38 mutex_lock(&inode->i_mutex);
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 inode->i_pipe->r_counter++;
59 if (inode->i_pipe->readers++ == 0)
60 wake_up_partner(inode);
62 if (!inode->i_pipe->writers) {
63 if ((filp->f_flags & O_NONBLOCK)) {
64 /* suppress POLLHUP until we have
66 filp->f_version = inode->i_pipe->w_counter;
69 wait_for_partner(inode, &inode->i_pipe->w_counter);
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) && !inode->i_pipe->readers)
86 filp->f_op = &write_fifo_fops;
87 inode->i_pipe->w_counter++;
88 if (!inode->i_pipe->writers++)
89 wake_up_partner(inode);
91 if (!inode->i_pipe->readers) {
92 wait_for_partner(inode, &inode->i_pipe->r_counter);
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 inode->i_pipe->readers++;
108 inode->i_pipe->writers++;
109 inode->i_pipe->r_counter++;
110 inode->i_pipe->w_counter++;
111 if (inode->i_pipe->readers == 1 || inode->i_pipe->writers == 1)
112 wake_up_partner(inode);
121 mutex_unlock(&inode->i_mutex);
125 if (!--inode->i_pipe->readers)
126 wake_up_interruptible(&inode->i_pipe->wait);
131 if (!--inode->i_pipe->writers)
132 wake_up_interruptible(&inode->i_pipe->wait);
137 if (!inode->i_pipe->readers && !inode->i_pipe->writers)
138 free_pipe_info(inode);
141 mutex_unlock(&inode->i_mutex);
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 */