From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932698AbcBZIZf (ORCPT ); Fri, 26 Feb 2016 03:25:35 -0500 Received: from mail-wm0-f44.google.com ([74.125.82.44]:38472 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932603AbcBZIZd (ORCPT ); Fri, 26 Feb 2016 03:25:33 -0500 Subject: Re: BUG: unable to handle kernel paging request from pty_write [was: Linux 4.4.2] To: Steven Rostedt , Linus Torvalds References: <20160217203730.GA14820@kroah.com> <56CED373.9060603@suse.cz> <56CF4A83.3040408@hurleysoftware.com> <20160225142338.42e46f2c@gandalf.local.home> Cc: Peter Hurley , Greg KH , Linux Kernel Mailing List , Andrew Morton , stable , lwn@lwn.net From: Jiri Slaby Message-ID: <56D00BFA.6060406@suse.cz> Date: Fri, 26 Feb 2016 09:25:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20160225142338.42e46f2c@gandalf.local.home> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/25/2016, 08:23 PM, Steven Rostedt wrote: > On Thu, 25 Feb 2016 11:09:35 -0800 > Linus Torvalds wrote: > > >> Jiri, were you messing around with tracing when this happened? Or >> maybe shutting down CPU's? There was a RCU locking problem with CPU >> shutdown, maybe this is one of the symptoms. The fix for that is >> recent, and not in 4.4.2. >> >> Adding Steven Rostedt to the cc. Steven, does that look like a possible case? > > Possible: yes. Likely: no > > The recent fix would require shutting down a CPU at the same time as a > tracepoint is enabled or disabled. Rather difficult to hit, but easier > on a virtual machine. If Jiri was not enabling/disabling tracepoints or > shutting down CPUs, then it would not be the bug. As this is an automatic build, I very doubt a CPU was offlined or tracepoints enabled. So I see it even less unlikely this to happen concurrently. > But as the comm of the bug is gdb and this running on a virtual > machine, I think the bug may be elsewhere. Corrupt stack possibly? Seems so (broken stack frame pointer link), as is indicated in other e-mail. thanks, -- js suse labs