From c65c9bc3efa5589f691276bb9db689119a711222 Mon Sep 17 00:00:00 2001 From: Alan Cox Date: Thu, 11 Jun 2009 12:50:12 +0100 Subject: tty: rewrite the ldisc locking There are several pretty much unfixable races in the old ldisc code, especially with respect to pty behaviour and also to hangup. It's easier to rewrite the code than simply try and patch it up. This patch - splits the ldisc from the tty (so we will be able to refcount it more cleanly later) - introduces a mutex lock for ldisc changing on an active device - fixes the complete mess that hangup caused - implements hopefully correct setldisc/close/hangup locking There are still some problems around pty pairs that have always been there but at least it is now possible to understand the code and fix further problems. This fixes the following known bugs - hang up can leak ldisc references - hang up may not call open/close on ldisc in a matched way - pty/tty pairs can deadlock during an ldisc change - reading the ldisc proc files can cause every ldisc to be loaded and probably a few other of the mysterious ldisc race reports. I'm sure it also adds the odd new one. Signed-off-by: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/n_hdlc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/char/n_hdlc.c') diff --git a/drivers/char/n_hdlc.c b/drivers/char/n_hdlc.c index bacb3e2872a..461ece591a5 100644 --- a/drivers/char/n_hdlc.c +++ b/drivers/char/n_hdlc.c @@ -342,8 +342,8 @@ static int n_hdlc_tty_open (struct tty_struct *tty) #endif /* Flush any pending characters in the driver and discipline. */ - if (tty->ldisc.ops->flush_buffer) - tty->ldisc.ops->flush_buffer(tty); + if (tty->ldisc->ops->flush_buffer) + tty->ldisc->ops->flush_buffer(tty); tty_driver_flush_buffer(tty); -- cgit v1.2.3-70-g09d2