From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755049Ab3BELkO (ORCPT ); Tue, 5 Feb 2013 06:40:14 -0500 Received: from mail-we0-f174.google.com ([74.125.82.174]:51973 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754940Ab3BELkL (ORCPT ); Tue, 5 Feb 2013 06:40:11 -0500 Message-ID: <5110EF95.4060402@suse.cz> Date: Tue, 05 Feb 2013 12:40:05 +0100 From: Jiri Slaby User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:19.0) Gecko/20130124 Thunderbird/19.0 MIME-Version: 1.0 To: Peter Hurley CC: Jiri Slaby , gregkh@linuxfoundation.org, alan@linux.intel.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 07/10] TTY: switch tty_schedule_flip References: <1357224789-2853-1-git-send-email-jslaby@suse.cz> <1357224789-2853-8-git-send-email-jslaby@suse.cz> <1359722247.3381.16.camel@thor.lan> <510BD9E9.9000400@suse.cz> <1359751171.22968.6.camel@thor.lan> In-Reply-To: <1359751171.22968.6.camel@thor.lan> X-Enigmail-Version: 1.5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/01/2013 09:39 PM, Peter Hurley wrote: > On Fri, 2013-02-01 at 16:06 +0100, Jiri Slaby wrote: >> On 02/01/2013 01:37 PM, Peter Hurley wrote: >>> On Thu, 2013-01-03 at 15:53 +0100, Jiri Slaby wrote: >>>> Now, we start converting tty buffer functions to actually use >>>> tty_port. This will allow us to get rid of the need of tty in many >>>> call sites. Only tty_port will needed and hence no more >>>> tty_port_tty_get in those paths. >>>> >>>> This is the last one: tty_schedule_flip >>> >>> [snip] >>> >>>> diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c >>>> index 5aace4d..a9af1b9a 100644 >>>> --- a/drivers/tty/vt/keyboard.c >>>> +++ b/drivers/tty/vt/keyboard.c >>>> @@ -307,26 +307,17 @@ int kbd_rate(struct kbd_repeat *rep) >>>> */ >>>> static void put_queue(struct vc_data *vc, int ch) >>>> { >>>> - struct tty_struct *tty = vc->port.tty; >>>> - >>>> tty_insert_flip_char(&vc->port, ch, 0); >>>> - if (tty) { >>>> - tty_schedule_flip(tty); >>>> - } >>>> + tty_schedule_flip(&vc->port); >>>> } >>>> >>>> static void puts_queue(struct vc_data *vc, char *cp) >>>> { >>>> - struct tty_struct *tty = vc->port.tty; >>>> - >>>> - if (!tty) >>>> - return; >>>> - >>>> while (*cp) { >>>> tty_insert_flip_char(&vc->port, *cp, 0); >>>> cp++; >>>> } >>>> - tty_schedule_flip(tty); >>>> + tty_schedule_flip(&vc->port); >>>> } >>> >>> Umm. So even though the vt driver knows the tty has been shutdown, >>> keystrokes will still be buffered? And then fed to whichever tty happens >>> to next get installed on the same port? >> >> Unless I completely missed something, they should be flushed. If that's >> not the case, that's a bug. I will check next week. > > Ok. > > I'm fairly sure this is happening. Try repeatedly tapping arrow-down > while booting (I suggest a VM) and you won't be able to login at tty1 > (ie, text mode). Repeatable 1 time in 5 or so. I can reproduce... with 3.0! Are you sure this is new and introduced by the tty buffers switch? > FWIW, I don't agree that the best way is to flush the flip buffers. Why > buffer and then schedule the cpu to do work which we already know it > can't do and which we're going to discard anyway? Because the drivers needn't care whether there is any tty behind and listening. This simplifies and speeds up the paths _a lot_. No spin locks, no ttys around, no two code paths etc. > In any event, since -next is already carrying these patches, and > by-design, these patches _expect_ the tty to be NULL, are you going to > remove the warning in flush_to_ldisc() or shall I? I think I don't understand you here, could you elaborate? thanks, -- js suse labs