From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: 3.8-rc regression with pps-ldisc due to 70ece7a731 Date: Wed, 06 Feb 2013 11:15:43 -0500 Message-ID: <1360167343.3298.56.camel@thor.lan> References: <20130204070805.28980.qmail@science.horizon.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from mailout39.mail01.mtsvc.net ([216.70.64.83]:34429 "EHLO n12.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756482Ab3BFQP7 (ORCPT ); Wed, 6 Feb 2013 11:15:59 -0500 In-Reply-To: <20130204070805.28980.qmail@science.horizon.com> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: George Spelvin Cc: jslaby@suse.cz, linux-serial@vger.kernel.org, giometti@linux.it, lasaine@lvk.cs.msu.su, linux-kernel@vger.kernel.org On Mon, 2013-02-04 at 02:08 -0500, George Spelvin wrote: > Just a quick update: the previously posted patch *does* work; > the crash I was experiencing was pilot error. > > My NTP server is running a 3.8.0-rc6-dirty kernel right now. > > I'll research whether that race I talk about in pps_tty_dcd_change > is actually possible or not (can interrupts start arriving before the > ->open() method returns?) and work out a finished minimal bugfix patch > if nobody else finds a better solution. You are not supposed to receive ldisc->dcd_change() calls outside the open()/close() pair. The ldisc is separately enabled/halted which is supposed to prevent ldisc usage if a ldisc reference cannot be acquired (because it's halted). The reference is acquired prior to calling the ->dcd_change() routine. In the patch series I sent, I changed the BUG_ON() to WARN_ON_ONCE(). Please reply to that patch with the snipped kernel log output if it warns in your testing and we'll go from there. > (Have I mentioned how ANNOYING it is when the kernel dumps more than > 50 lines of crash message to the console screen and then locks > the keyboard so I can't scroll back?) netconsole on 2nd machine (see Documentation/networking/netconsole.txt) Regards, Peter Hurley