From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF35BC433F5 for ; Sat, 25 Aug 2018 02:41:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 522E9208B2 for ; Sat, 25 Aug 2018 02:41:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 522E9208B2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726574AbeHYGSm (ORCPT ); Sat, 25 Aug 2018 02:18:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:34744 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726110AbeHYGSl (ORCPT ); Sat, 25 Aug 2018 02:18:41 -0400 Received: from vmware.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4ECF9208B2; Sat, 25 Aug 2018 02:41:24 +0000 (UTC) Date: Fri, 24 Aug 2018 22:41:22 -0400 From: Steven Rostedt To: Masami Hiramatsu Cc: Shuah Khan , Ingo Molnar , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 24/32] selftests/ftrace: Add max stack tracer testcase Message-ID: <20180824224122.2e10e7f9@vmware.local.home> In-Reply-To: <20180825104509.1b739d5d17d860e453daa0ca@kernel.org> References: <153443695002.23257.13628220023468200991.stgit@devbox> <153443763074.23257.4052504725796725062.stgit@devbox> <20180824192352.262144f5@gandalf.local.home> <20180825104509.1b739d5d17d860e453daa0ca@kernel.org> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.32; 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 25 Aug 2018 10:45:09 +0900 Masami Hiramatsu wrote: > On Fri, 24 Aug 2018 19:23:52 -0400 > Steven Rostedt wrote: > > > On Fri, 17 Aug 2018 01:40:30 +0900 > > Masami Hiramatsu wrote: > > > > > Add a testcase for max stack tracer, which checks basic > > > max stack usage tracing and its filter feature. > > > > > > Signed-off-by: Masami Hiramatsu > > > --- > > > .../ftrace/test.d/ftrace/func_stack_tracer.tc | 39 ++++++++++++++++++++ > > > 1 file changed, 39 insertions(+) > > > create mode 100644 tools/testing/selftests/ftrace/test.d/ftrace/func_stack_tracer.tc > > > > > > diff --git a/tools/testing/selftests/ftrace/test.d/ftrace/func_stack_tracer.tc b/tools/testing/selftests/ftrace/test.d/ftrace/func_stack_tracer.tc > > > new file mode 100644 > > > index 000000000000..b414f0e3c646 > > > --- /dev/null > > > +++ b/tools/testing/selftests/ftrace/test.d/ftrace/func_stack_tracer.tc > > > @@ -0,0 +1,39 @@ > > > +#!/bin/sh > > > +# SPDX-License-Identifier: GPL-2.0 > > > +# description: ftrace - Max stack tracer > > > +# Test the basic function of max-stack usage tracing > > > + > > > +if [ ! -f stack_trace ]; then > > > + echo "Max stack tracer is not supported - please make CONFIG_STACK_TRACER=y" > > > + exit_unsupported > > > +fi > > > + > > > +echo > stack_trace_filter > > > +echo 0 > stack_max_size > > > +echo 1 > /proc/sys/kernel/stack_tracer_enabled > > > + > > > +: "Fork and wait for the first entry become !lock" > > > +timeout=10 > > > +while [ $timeout -ne 0 ]; do > > > + ( echo "forked" ) > > > + FL=`grep " 0)" stack_trace` > > > + echo $FL | grep -q "lock" || break; > > > + timeout=$((timeout - 1)) > > > +done > > > +echo 0 > /proc/sys/kernel/stack_tracer_enabled > > > + > > > +echo '*lock*' > stack_trace_filter > > > +test `cat stack_trace_filter | wc -l` -eq `grep lock stack_trace_filter | wc -l` > > > + > > > +echo 0 > stack_max_size > > > +echo 1 > /proc/sys/kernel/stack_tracer_enabled > > > > This test fails quite a bit because it doesn't guarantee that another > > stack trace gets in that is bigger, and we don't find the "lock". > > Hmm, maybe I misunderstand what is the stack_trace_filter. > I thought it filtered the function that triggered stack trace, > so the top of stack trace was always filtered function. > If not, what does this filter? Ah, I missed the filter part, no its correct, and actually found a bug ;-) By adding this patch, it works again: diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index 4237eba4ef20..2b0d1ee3241c 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -111,7 +111,7 @@ check_stack(unsigned long ip, unsigned long *stack) stack_trace_max_size = this_size; stack_trace_max.nr_entries = 0; - stack_trace_max.skip = 3; + stack_trace_max.skip = 0; save_stack_trace(&stack_trace_max); -- Steve > > > > > + > > > +: "Fork and always the first entry including lock" > > > +timeout=10 > > > +while [ $timeout -ne 0 ]; do > > > + ( echo "forked" ) > > > + FL=`grep " 0)" stack_trace` > > > + echo $FL | grep -q "lock" > > > + timeout=$((timeout - 1)) > > > +done > > > +echo 0 > /proc/sys/kernel/stack_tracer_enabled > > > >