From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751908AbcGMACe (ORCPT ); Tue, 12 Jul 2016 20:02:34 -0400 Received: from mga04.intel.com ([192.55.52.120]:11671 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750784AbcGMACZ (ORCPT ); Tue, 12 Jul 2016 20:02:25 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,354,1464678000"; d="scan'208";a="733321928" Date: Wed, 13 Jul 2016 08:01:55 +0800 From: Fengguang Wu To: Daniel Borkmann Cc: kbuild-all@01.org, davem@davemloft.net, alexei.starovoitov@gmail.com, peterz@infradead.org, tgraf@suug.ch, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 3/3] bpf: avoid stack copy and use skb ctx for event output Message-ID: <20160713000155.GA20432@wfg-t540p.sh.intel.com> References: <201607130750.HlB4VMOA%fengguang.wu@intel.com> <5785812B.4080505@iogearbox.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <5785812B.4080505@iogearbox.net> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Daniel, On Wed, Jul 13, 2016 at 01:45:47AM +0200, Daniel Borkmann wrote: >On 07/13/2016 01:25 AM, kbuild test robot wrote: >> Hi, >> >> [auto build test WARNING on net-next/master] >> >> url: https://github.com/0day-ci/linux/commits/Daniel-Borkmann/BPF-event-output-helper-improvements/20160713-065944 >> config: s390-allyesconfig (attached as .config) >> compiler: s390x-linux-gnu-gcc (Debian 5.3.1-8) 5.3.1 20160205 >> reproduce: >> wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross >> chmod +x ~/bin/make.cross >> # save the attached .config to linux build tree >> make.cross ARCH=s390 >> >> All warnings (new ones prefixed by >>): >> >> kernel/trace/bpf_trace.c: In function 'bpf_perf_event_output': >> kernel/trace/bpf_trace.c:284:1: warning: 'bpf_perf_event_output' uses dynamic stack allocation >> } >> ^ >> kernel/trace/bpf_trace.c: In function 'bpf_event_output': >>>> kernel/trace/bpf_trace.c:319:1: warning: 'bpf_event_output' uses dynamic stack allocation >> } >> ^ > >Hmm, searching a bit on lkml, it seems these warnings on s390 are actually mostly >harmless I believe [1][2] ... looks like they are there to find structs sitting >on stack, for example, at least that's also what the currently existing one in the >above line (bpf_trace.c +284) appears to be about. Yes it does look so. All such warnings happen only in s390: % g -h -o '[^ ]*config' *dynamic-stack* | sort | uniq -c | sort -nr 118 s390-allyesconfig 80 s390-allmodconfig Let's ignore all of them on s390. Thanks, Fengguang > [1] http://lkml.iu.edu/hypermail/linux/kernel/1601.2/04074.html > [2] https://lkml.org/lkml/2013/6/25/42