[ I'm cc:ing this to Al Viro, who (despite his protestations to the
contrary) seems to be the closest thing we have to an FS subsystem
maintainer :-) ]
The patch below lets userspace apps do SIGIO-driven I/O on FIFOs and
pipes. The semantics are the same as for existing SIGIO-capable
devices such as sockets. The lack of SIGIO has broken things before
(e.g., http://www.uwsg.iu.edu/hypermail/linux/kernel/0004.3/0179.html
and
http://linux.ucla.edu/pipermail/linux/2001-August/005646.html).
I originally posted this patch (against 2.4.x) to the list last
August, and since then have heard from a half-dozen people who have
used it successfully. Our lab's 30 workstations have been using it
for 9 months with no problems under 2.4.9. So, I thought I'd ping the
list again and see if there's any interest in integrating it with the
main line kernel.
The patches for 2.5.7 and 2.4.x are available at:
http://www.circlemud.org/~jelson/linux/fifo-sigio-2.5.7.patch
http://www.circlemud.org/~jelson/linux/fifo-sigio-2.4.patch
The 2.5.7 patch is also attached below.
Best,
Jeremy
diff -u --recursive linux-2.5.7-orig/fs/pipe.c linux-2.5.7/fs/pipe.c
--- linux-2.5.7-orig/fs/pipe.c Mon Mar 18 12:37:02 2002
+++ linux-2.5.7/fs/pipe.c Mon Apr 1 20:47:10 2002
@@ -22,6 +22,9 @@
*
* Reads with count = 0 should always return 0.
* -- Julian Bradfield 1999-06-07.
+ *
+ * FIFOs and Pipes now generate SIGIO for both readers and writers.
+ * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
*/
/* Drop the inode semaphore and wait for a pipe event, atomically */
@@ -117,12 +120,14 @@
* room.
*/
wake_up_interruptible(PIPE_WAIT(*inode));
+ kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
if (!PIPE_EMPTY(*inode))
BUG();
goto do_more_read;
}
/* Signal writers asynchronously that there is more room. */
wake_up_interruptible(PIPE_WAIT(*inode));
+ kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
ret = read;
out:
@@ -215,6 +220,7 @@
* to do idle reschedules.
*/
wake_up_interruptible(PIPE_WAIT(*inode));
+ kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
PIPE_WAITING_WRITERS(*inode)++;
pipe_wait(inode);
PIPE_WAITING_WRITERS(*inode)--;
@@ -228,6 +234,7 @@
/* Signal readers asynchronously that there is more data. */
wake_up_interruptible(PIPE_WAIT(*inode));
+ kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
inode->i_ctime = inode->i_mtime = CURRENT_TIME;
mark_inode_dirty(inode);
@@ -308,6 +315,8 @@
kfree(info);
} else {
wake_up_interruptible(PIPE_WAIT(*inode));
+ kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
+ kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
}
up(PIPE_SEM(*inode));
@@ -315,14 +324,72 @@
}
static int
+pipe_read_fasync(int fd, struct file *filp, int on)
+{
+ struct inode *inode = filp->f_dentry->d_inode;
+ int retval;
+
+ down(PIPE_SEM(*inode));
+ retval = fasync_helper(fd, filp, on, PIPE_FASYNC_READERS(*inode));
+ up(PIPE_SEM(*inode));
+
+ if (retval < 0)
+ return retval;
+
+ return 0;
+}
+
+
+static int
+pipe_write_fasync(int fd, struct file *filp, int on)
+{
+ struct inode *inode = filp->f_dentry->d_inode;
+ int retval;
+
+ down(PIPE_SEM(*inode));
+ retval = fasync_helper(fd, filp, on, PIPE_FASYNC_WRITERS(*inode));
+ up(PIPE_SEM(*inode));
+
+ if (retval < 0)
+ return retval;
+
+ return 0;
+}
+
+
+static int
+pipe_rdwr_fasync(int fd, struct file *filp, int on)
+{
+ struct inode *inode = filp->f_dentry->d_inode;
+ int retval;
+
+ down(PIPE_SEM(*inode));
+
+ retval = fasync_helper(fd, filp, on, PIPE_FASYNC_READERS(*inode));
+
+ if (retval >= 0)
+ retval = fasync_helper(fd, filp, on, PIPE_FASYNC_WRITERS(*inode));
+
+ up(PIPE_SEM(*inode));
+
+ if (retval < 0)
+ return retval;
+
+ return 0;
+}
+
+
+static int
pipe_read_release(struct inode *inode, struct file *filp)
{
+ pipe_read_fasync(-1, filp, 0);
return pipe_release(inode, 1, 0);
}
static int
pipe_write_release(struct inode *inode, struct file *filp)
{
+ pipe_write_fasync(-1, filp, 0);
return pipe_release(inode, 0, 1);
}
@@ -331,6 +398,7 @@
{
int decr, decw;
+ pipe_rdwr_fasync(-1, filp, 0);
decr = (filp->f_mode & FMODE_READ) != 0;
decw = (filp->f_mode & FMODE_WRITE) != 0;
return pipe_release(inode, decr, decw);
@@ -383,6 +451,7 @@
ioctl: pipe_ioctl,
open: pipe_read_open,
release: pipe_read_release,
+ fasync: pipe_read_fasync,
};
struct file_operations write_fifo_fops = {
@@ -393,6 +462,7 @@
ioctl: pipe_ioctl,
open: pipe_write_open,
release: pipe_write_release,
+ fasync: pipe_write_fasync,
};
struct file_operations rdwr_fifo_fops = {
@@ -403,6 +473,7 @@
ioctl: pipe_ioctl,
open: pipe_rdwr_open,
release: pipe_rdwr_release,
+ fasync: pipe_rdwr_fasync,
};
struct file_operations read_pipe_fops = {
@@ -413,6 +484,7 @@
ioctl: pipe_ioctl,
open: pipe_read_open,
release: pipe_read_release,
+ fasync: pipe_read_fasync,
};
struct file_operations write_pipe_fops = {
@@ -423,6 +495,7 @@
ioctl: pipe_ioctl,
open: pipe_write_open,
release: pipe_write_release,
+ fasync: pipe_write_fasync,
};
struct file_operations rdwr_pipe_fops = {
@@ -433,6 +506,7 @@
ioctl: pipe_ioctl,
open: pipe_rdwr_open,
release: pipe_rdwr_release,
+ fasync: pipe_rdwr_fasync,
};
struct inode* pipe_new(struct inode* inode)
@@ -453,6 +527,7 @@
PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 0;
PIPE_WAITING_READERS(*inode) = PIPE_WAITING_WRITERS(*inode) = 0;
PIPE_RCOUNTER(*inode) = PIPE_WCOUNTER(*inode) = 1;
+ *PIPE_FASYNC_READERS(*inode) = *PIPE_FASYNC_WRITERS(*inode) = NULL;
return inode;
fail_page:
-
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This archive was generated by hypermail 2b29 : Sun Apr 07 2002 - 22:00:09 EST