From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753619AbaDCUpH (ORCPT ); Thu, 3 Apr 2014 16:45:07 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:21046 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753541AbaDCUpE (ORCPT ); Thu, 3 Apr 2014 16:45:04 -0400 Message-ID: <533DC7F5.9090202@oracle.com> Date: Thu, 03 Apr 2014 16:43:33 -0400 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Peter Zijlstra , Steven Rostedt CC: Sasha Levin , Dave Jones , Tejun Heo , tglx@linutronix.de, LKML , trinity@vger.kernel.org Subject: Re: timer: lockup in run_timer_softirq() References: <51DC9379.9050408@oracle.com> <20130709230316.GB13855@redhat.com> <51DC983F.2010409@oracle.com> <20130710095210.GD17211@twins.programming.kicks-ass.net> <1373459254.7458.49.camel@gandalf.local.home> <20130710124245.GT25631@dyad.programming.kicks-ass.net> <1373461091.7458.55.camel@gandalf.local.home> <20130711164204.GK25631@dyad.programming.kicks-ass.net> <1373561726.17876.48.camel@gandalf.local.home> <1373561972.17876.51.camel@gandalf.local.home> <20130711171157.GL25631@dyad.programming.kicks-ass.net> In-Reply-To: <20130711171157.GL25631@dyad.programming.kicks-ass.net> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/11/2013 01:11 PM, Peter Zijlstra wrote: > On Thu, Jul 11, 2013 at 12:59:32PM -0400, Steven Rostedt wrote: >> On Thu, 2013-07-11 at 12:55 -0400, Steven Rostedt wrote: >> >>>> >>>> Other than that, a function tracer environment that is safer to use might be >>>> useful for other people as well. >>> >>> Not sure how to make the environment safe, as the main purpose of the >>> function trace is to debug those hard to debug locations, like NMIs, >>> RCU, dynamic ticks, etc. To ensure a "safe" environment, it would >>> cripple the tracer. >>> >>> Hmm, what would you state as a safe environment? How can we detect if >>> the environment is safe to trace or not? >> >> Maybe I misunderstood you. You mean to have this environment be >> something for not just perf, and have the macro be: >> >> NONSAFE_TRACE(__local_bh_enable); >> >> ? >> >> Then, any ftrace user could set a flag in the registering of its ops to >> 'safe_only_functions'. And it will ignore all of these locations. >> There's really not many of them, so it may not be too hard to weed out. > > Yah, like that. But that doesn't invalidate your question as to what 'safe' > would encompass. I think RCU/lockdep would be the big thing for perf, not > sure it should be wider than that. Ping? There was no conclusion here and this issue is still ongoing in -next. Thanks, Sasha