From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750844AbWGVQR2 (ORCPT ); Sat, 22 Jul 2006 12:17:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750852AbWGVQR2 (ORCPT ); Sat, 22 Jul 2006 12:17:28 -0400 Received: from liaag1ab.mx.compuserve.com ([149.174.40.28]:19937 "EHLO liaag1ab.mx.compuserve.com") by vger.kernel.org with ESMTP id S1750843AbWGVQR2 (ORCPT ); Sat, 22 Jul 2006 12:17:28 -0400 Date: Sat, 22 Jul 2006 12:07:00 -0400 From: Chuck Ebbert <76306.1226@compuserve.com> Subject: Re: Success: tty_io flush_to_ldisc() error message triggered To: Paul Fulghum Cc: Alan Cox , linux-kernel , linux-stable Message-ID: <200607221209_MC3-1-C5CA-50EB@compuserve.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org In-Reply-To: <44C2307C.9060607@microgate.com> On Sat, 22 Jul 2006 09:04:44 -0500, Paul Fulghum wrote: > That confirms my thoughts on what went wrong: > multiple copies of the queued work (flush_to_ldisc) > running in parallel and corrupting the free buffer list. > > A cleaner fix for this is already > in the 2.6.18 rc series. The cleaner fix looks more intrusive, though. Is this simpler change (what I'm running but without the warning messages) the preferred fix for -stable? From: Paul Fulghum Serialize flush_to_ldisc() per-device. Fixes free list corruption that causes lockup on SMP systems. Signed-off-by: Paul Fulghum Acked-by: Chuck Ebbert <76306.1226@compuserve.com> --- 2.6.16.20-d4.orig/include/linux/tty.h +++ 2.6.16.20-d4/include/linux/tty.h @@ -266,6 +266,7 @@ struct tty_struct { #define TTY_PTY_LOCK 16 /* pty private */ #define TTY_NO_WRITE_SPLIT 17 /* Preserve write boundaries to driver */ #define TTY_HUPPED 18 /* Post driver->hangup() */ +#define TTY_FLUSHING 19 /* Flushing tty buffers to line discipline */ #define TTY_WRITE_FLUSH(tty) tty_write_flush((tty)) --- 2.6.16.20-d4.orig/drivers/char/tty_io.c +++ 2.6.16.20-d4/drivers/char/tty_io.c @@ -2780,10 +2780,8 @@ static void flush_to_ldisc(void *private if (disc == NULL) /* !TTY_LDISC */ return; - if (test_bit(TTY_DONT_FLIP, &tty->flags)) { - /* - * Do it after the next timer tick: - */ + if (test_bit(TTY_DONT_FLIP, &tty->flags) || + test_and_set_bit(TTY_FLUSHING, &tty->flags)) { schedule_delayed_work(&tty->buf.work, 1); goto out; } @@ -2805,6 +2803,7 @@ static void flush_to_ldisc(void *private tty_buffer_free(tty, tbuf); } spin_unlock_irqrestore(&tty->buf.lock, flags); + clear_bit(TTY_FLUSHING, &tty->flags); out: tty_ldisc_deref(disc); } -- Chuck