Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753245AbdHBL4y (ORCPT ); Wed, 2 Aug 2017 07:56:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:53440 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753122AbdHBL4x (ORCPT ); Wed, 2 Aug 2017 07:56:53 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ABC9022BE4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Wed, 2 Aug 2017 07:56:50 -0400 From: Steven Rostedt To: Pratyush Anand Cc: open list Subject: Re: Query: rcu_sched detected stalls with function_graph tracer Message-ID: <20170802075650.7dab7586@gandalf.local.home> In-Reply-To: References: X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1215 Lines: 30 On Wed, 2 Aug 2017 12:02:21 +0530 Pratyush Anand wrote: > Hi Steve, > > I am using a 3.10 based kernel, and when I enable function_graph with one > particular x86_64 machine, I encounter rcu_sched stall. > > echo function_graph > /sys/kernel/debug/tracing/current_tracer > echo 1 > /sys/kernel/debug/tracing/tracing_on > > If I use 4.13-rc2, then its better, but still goes for it after a bit of > stressing with stressng. > > It looks like that this behavior should be expected with a loaded system (like > that of ftrace-graph tracing for all available function) which can cause RCU > stall warning. But,I am not an expert. So, whats your opinion on it? > > I tried to bisect and there was no particular function which can cause this. > It looked like that when we had more than 5000 functions in set_ftrace_filter, > we start getting such warnings. Tried by putting some most hit functions like > spin_lock* etc in set_ftrace_notrace. Still, no help. Do you have some > suggestion for further debugging pointers? > > log with 3.10 based kernel Can you send me the config. I'm also guessing that this is a RHEL 3.10 based kernel (which means it's not 3.10 at all). -- Steve