[PATCH] tty flush flip buffer on ldisc input queue flush

[PATCH] tty flush flip buffer on ldisc input queue flush

[Paul Fulghum]

Flush the tty flip buffer when the line discipline
input queue is flushed, including the user call
tcflush(TCIFLUSH/TCIOFLUSH). This prevents unexpected
stale data after a user application calls tcflush().

Cc: Alan Cox <alan@lxorguk.org.uk>
Cc: Antonino Ingargiola <tritemio@gmail.com>
Signed-off-by: Paul Fulghum <paulkf@microgate.com>

--- a/drivers/char/tty_io.c	2007-05-04 05:46:55.000000000 -0500
+++ b/drivers/char/tty_io.c	2007-05-05 03:23:46.000000000 -0500
@@ -365,6 +365,29 @@ static void tty_buffer_free(struct tty_s
 }
 
 /**
+ *	tty_buffer_flush		-	flush full tty buffers
+ *	@tty: tty to flush
+ *
+ *	flush all the buffers containing receive data
+ *
+ *	Locking: none
+ */
+
+static void tty_buffer_flush(struct tty_struct *tty)
+{
+	struct tty_buffer *thead;
+	unsigned long flags;
+
+	spin_lock_irqsave(&tty->buf.lock, flags);
+	while((thead = tty->buf.head) != NULL) {
+		tty->buf.head = thead->next;
+		tty_buffer_free(tty, thead);
+	}
+	tty->buf.tail = NULL;
+	spin_unlock_irqrestore(&tty->buf.lock, flags);
+}
+
+/**
  *	tty_buffer_find		-	find a free tty buffer
  *	@tty: tty owning the buffer
  *	@size: characters wanted
@@ -1240,6 +1263,7 @@ void tty_ldisc_flush(struct tty_struct *
 			ld->flush_buffer(tty);
 		tty_ldisc_deref(ld);
 	}
+	tty_buffer_flush(tty);
 }
 
 EXPORT_SYMBOL_GPL(tty_ldisc_flush);
@@ -3336,6 +3360,15 @@ int tty_ioctl(struct inode * inode, stru
 		case TIOCMBIC:
 		case TIOCMBIS:
 			return tty_tiocmset(tty, file, cmd, p);
+		case TCFLSH:
+			switch (arg) {
+			case TCIFLUSH:
+			case TCIOFLUSH:
+				/* flush tty buffer and allow ldisc to process ioctl */
+				tty_buffer_flush(tty);
+				break;
+			}
+			break;
 	}
 	if (tty->driver->ioctl) {
 		retval = (tty->driver->ioctl)(tty, file, cmd, arg);

[PATCH] isdn/i4l: 'NO CARRIER' message lost after ldisc flush

[Matthias Goebl]

The ISDN tty layer doesn't produce a 'NO CARRIER' message after hangup.

I suppose it broke when tty_buffer_flush() has been added to
tty_ldisc_flush() in the commit below.

For isdn_tty_modem_result(RESULT_NO_CARRIER..) the
message inserted via isdn_tty_at_cout() -> tty_insert_flip_char()
is flushed immediately by tty_ldisc_flush() -> tty_buffer_flush().
More annoyingly, the audio abort sequence DLE-ETX is also lost.

This patch fixes only active audio connections, because I assume that nobody
changes the line discipline for audio.

For non-audio connections the problem remains.
Maybe we can remove the tty_ldisc_flush() in isdn_tty_modem_result()
at all because it's done at tty_close?


On Mon, May 07, 2007 at 04:05:57PM -0500, Paul Fulghum wrote:
> Flush the tty flip buffer when the line discipline
> input queue is flushed, including the user call
> tcflush(TCIFLUSH/TCIOFLUSH). This prevents unexpected
> stale data after a user application calls tcflush().
> 
> Cc: Alan Cox <alan@lxorguk.org.uk>
> Cc: Antonino Ingargiola <tritemio@gmail.com>
> Signed-off-by: Paul Fulghum <paulkf@microgate.com>
> 
> --- a/drivers/char/tty_io.c	2007-05-04 05:46:55.000000000 -0500
> +++ b/drivers/char/tty_io.c	2007-05-05 03:23:46.000000000 -0500
> @@ -1240,6 +1263,7 @@ void tty_ldisc_flush(struct tty_struct *
>  			ld->flush_buffer(tty);
>  		tty_ldisc_deref(ld);
>  	}
> +	tty_buffer_flush(tty);
[..]


Signed-off-by: Matthias Goebl <matthias.goebl@goebl.net>

--- linux-2.6.23.12.orig/drivers/isdn/i4l/isdn_tty.c	
+++ linux-2.6.23.12/drivers/isdn/i4l/isdn_tty.c	
@@ -2645,7 +2649,12 @@
 		if ((info->flags & ISDN_ASYNC_CLOSING) || (!info->tty)) {
 			return;
 		}
+#ifdef CONFIG_ISDN_AUDIO
+		if ( !info->vonline )
+			tty_ldisc_flush(info->tty);
+#else
 		tty_ldisc_flush(info->tty);
+#endif
 		if ((info->flags & ISDN_ASYNC_CHECK_CD) &&
 		    (!((info->flags & ISDN_ASYNC_CALLOUT_ACTIVE) &&
 		       (info->flags & ISDN_ASYNC_CALLOUT_NOHUP)))) {

Re: [PATCH] isdn/i4l: 'NO CARRIER' message lost after ldisc flush

[Alan Cox]

> For non-audio connections the problem remains.
> Maybe we can remove the tty_ldisc_flush() in isdn_tty_modem_result()
> at all because it's done at tty_close?

I'm not sure I understand why the tty_ldisc_flush is being done in the
ISDN layer at this point but this change looks fine to me.


Alan

Re: [PATCH] isdn/i4l: 'NO CARRIER' message lost after ldisc flush

[David Miller]

From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Date: Thu, 3 Jan 2008 22:30:54 +0000

> > For non-audio connections the problem remains.
> > Maybe we can remove the tty_ldisc_flush() in isdn_tty_modem_result()
> > at all because it's done at tty_close?
> 
> I'm not sure I understand why the tty_ldisc_flush is being done in the
> ISDN layer at this point but this change looks fine to me.

I'll apply this fix to net-2.6 and push to Linus.

Thanks.