155 lines
3.2 KiB
C
155 lines
3.2 KiB
C
/*
|
|
* 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/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 FMODE_READ:
|
|
/*
|
|
* 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 FMODE_WRITE:
|
|
/*
|
|
* 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 FMODE_READ | FMODE_WRITE:
|
|
/*
|
|
* 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 */
|
|
};
|