tty: Flush ldisc buffer atomically with tty flip buffers
tty_ldisc_flush() first clears the line discipline input buffer,
then clears the tty flip buffers. However, this allows for existing
data in the tty flip buffers to be added after the ldisc input
buffer has been cleared, but before the flip buffers have been cleared.
Add an optional ldisc parameter to tty_buffer_flush() to allow
tty_ldisc_flush() to pass the ldisc to clear.
NB: Initially, the plan was to do this automatically in
tty_buffer_flush(). However, an audit of the behavior of existing
line disciplines showed that performing a ldisc buffer flush on
ioctl(TCFLSH) was not always the outcome. For example, some line
disciplines have flush_buffer() methods but not ioctl() methods,
so a ->flush_buffer() command would be unexpected.
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 6368dd9..b66a81d 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -397,19 +397,17 @@
* tty_ldisc_flush - flush line discipline queue
* @tty: tty
*
- * Flush the line discipline queue (if any) for this tty. If there
- * is no line discipline active this is a no-op.
+ * Flush the line discipline queue (if any) and the tty flip buffers
+ * for this tty.
*/
void tty_ldisc_flush(struct tty_struct *tty)
{
struct tty_ldisc *ld = tty_ldisc_ref(tty);
- if (ld) {
- if (ld->ops->flush_buffer)
- ld->ops->flush_buffer(tty);
+
+ tty_buffer_flush(tty, ld);
+ if (ld)
tty_ldisc_deref(ld);
- }
- tty_buffer_flush(tty);
}
EXPORT_SYMBOL_GPL(tty_ldisc_flush);