From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934734Ab0CLXeK (ORCPT ); Fri, 12 Mar 2010 18:34:10 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:42586 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933475Ab0CLXeI (ORCPT ); Fri, 12 Mar 2010 18:34:08 -0500 X-Authority-Analysis: v=1.0 c=1 a=8OTfl9jic9UA:10 a=ORa4HqFjfvEA:10 a=Q9fys5e9bTEA:10 a=fNZBj6YFGwC8gW0x7aEA:9 a=yyMLeY2KK0gipDPNFbYUR4_ApQkA:4 a=PUjeQqilurYA:10 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.89.75 Subject: Re: Using tracing_off() in __schedule_bug() From: Steven Rostedt To: Chase Douglas Cc: linux-kernel@vger.kernel.org, kernel-team In-Reply-To: <40ec3ea41003120732w5f44a2ebq728047e742f32bba@mail.gmail.com> References: <40ec3ea41003120732w5f44a2ebq728047e742f32bba@mail.gmail.com> Content-Type: text/plain; charset="ISO-8859-15" Date: Fri, 12 Mar 2010 18:34:04 -0500 Message-ID: <1268436844.4471.783.camel@gandalf.stny.rr.com> Mime-Version: 1.0 X-Mailer: Evolution 2.28.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2010-03-12 at 10:32 -0500, Chase Douglas wrote: > We're considering using tracing_off() in __schedule_bug() in the > Ubuntu kernel to help us solve "scheduling while atomic" bugs without > needing to compile and install a special kernel to do so. Using the > tracing_off() call enables us to generate smaller function traces when > debugging, and find the bug easier since it should be at the end of > any traces. The patch we are thinking of using can be found at [1]. > You can find an overview of how bugs are solved using this approach > there as well. > > Are there any thoughts as to the appropriateness of this patch in > Ubuntu kernels? My guess is that this isn't done in the upstream > vanilla kernels because it would be annoying to have a stock kernel > littered with tracing_off() calls if you hit one when you weren't > meaning to. However, we're interested in hearing if there's some > negative consequence we haven't thought of. Actually, it has been on my TODO list to litter tracing_off() all over the kernel ;-) No, by all means, I would definitely take a patch that turn off tracing at critical areas. One of which I would like to do is with the BUG() call. Hmm, thinking about it more, I would rather have a separate function, that would call tracing_off() if some variable is set. By default it would be set, but in case you want to keep tracing after a bug is hit, you can have a way to disable it. I need to write up a patch soon. Thanks for bring this up. -- Steve