Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754184Ab3GJM6O (ORCPT ); Wed, 10 Jul 2013 08:58:14 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:24401 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752430Ab3GJM6N (ORCPT ); Wed, 10 Jul 2013 08:58:13 -0400 X-Authority-Analysis: v=2.0 cv=Tr1kdUrh c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=mY5AGG0wUPsA:10 a=5SG0PmZfjMsA:10 a=IkcTkHD0fZMA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=x45eBLDEq7QA:10 a=9eVWKDxGWOiRCeP2OfoA:9 a=QEXdDO2ut3YA:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-ID: <1373461091.7458.55.camel@gandalf.local.home> Subject: Re: timer: lockup in run_timer_softirq() From: Steven Rostedt To: Peter Zijlstra Cc: Sasha Levin , Dave Jones , Tejun Heo , tglx@linutronix.de, LKML , trinity@vger.kernel.org Date: Wed, 10 Jul 2013 08:58:11 -0400 In-Reply-To: <20130710124245.GT25631@dyad.programming.kicks-ass.net> References: <51DC902F.3070403@oracle.com> <20130709224706.GA13855@redhat.com> <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> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4-3 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1341 Lines: 40 On Wed, 2013-07-10 at 14:42 +0200, Peter Zijlstra wrote: > but but but preempt_disable_notrace() isn't an rcu_read_lock().. You can only > do that for rcu_sched. Right. And not even rcu_sched is safe, as function tracing can trace functions out of rcu scope. That's why I had to add that code to do a schedule_on_each_cpu() in ftrace. > > Anyway, I don't see a nice way out of this mess :/ the entire perf core uses > regular RCU and converting all that is going to me a nasty big patch. There is an easier way. We can add a way to have perf not trace specific functions. Now there's already infrastructure there to pick and choose what to trace and what not to for individual function tracing users like perf. The trick will be how to annotate them. If there's a way to mark a function without moving it to a section, this would be possible. Perhaps similar to EXPORT_SYMBOL(). We could add a PERF_NOTRACE(). static void __local_bh_enable() { [...] } PERF_NOTRACE(__local_bh_enable); And add these to a black list of functions that perf should not trace. How's that sound? -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/