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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 D234CC6778F for ; Thu, 26 Jul 2018 02:21:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8D56920852 for ; Thu, 26 Jul 2018 02:21:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8D56920852 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au 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 S1728795AbeGZDf1 (ORCPT ); Wed, 25 Jul 2018 23:35:27 -0400 Received: from ozlabs.org ([203.11.71.1]:43657 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728485AbeGZDf1 (ORCPT ); Wed, 25 Jul 2018 23:35:27 -0400 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPSA id 41bbRq179Qz9ryl; Thu, 26 Jul 2018 12:20:55 +1000 (AEST) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au From: Michael Ellerman To: Murilo Opsfelder Araujo , Michael Neuling Cc: linux-kernel@vger.kernel.org, Alastair D'Silva , Andrew Donnellan , Balbir Singh , Benjamin Herrenschmidt , Christophe Leroy , Cyril Bur , "Eric W . Biederman" , Nicholas Piggin , Paul Mackerras , Simon Guo , Sukadev Bhattiprolu , "Tobin C . Harding" , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 0/7] powerpc: Modernize unhandled signals message In-Reply-To: <20180725193647.GA23643@kermit-br-ibm-com> References: <20180724192720.32417-1-muriloo@linux.ibm.com> <0f185351330a7f1d66409fe6a2dc02aae6826039.camel@neuling.org> <20180725193647.GA23643@kermit-br-ibm-com> Date: Thu, 26 Jul 2018 12:20:52 +1000 Message-ID: <87wotihh4r.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Murilo Opsfelder Araujo writes: > On Wed, Jul 25, 2018 at 05:00:21PM +1000, Michael Neuling wrote: >> On Tue, 2018-07-24 at 16:27 -0300, Murilo Opsfelder Araujo wrote: >> > This series was inspired by the need to modernize and display more >> > informative messages about unhandled signals. ... >> >> Nice.. the instruction dump would have been very handy when debugging the PCR >> init issue I had a month or so back. These things may be related :) >> What happens if we get a sudden flood of these from different processes that >> overlap their output? Are we going to be able to match up the process with >> instruction dump? > > As to the flood of messages, ___ratelimit() makes me think that we'll > likely see some warn messages informing how many show_signal_msg() > callbacks were suppressed, instead of interleaved messages and > instruction dumps. > > As to matching process with instruction dump, I believe we'd need more > information to glue them together. > > What if we modify show_instructions() to accept a string prefix to be > printed along with each line? > >> Should we prefix every line with the PID to avoid this? > > That's possible. An alternative would be prefixing each line with the > process name and its PID, as in the first line. For example: > > pandafault[10758]: segfault (11) at 00000000100007d0 nip 000000001000061c lr 00007fffabc85100 code 2 in pandafault[10000000+10000] > pandafault[10758]: Instruction dump: > pandafault[10758]: 4bfffeec 4bfffee8 3c401002 38427f00 fbe1fff8 f821ffc1 7c3f0b78 3d22fffe > pandafault[10758]: 392988d0 f93f0020 e93f0020 39400048 <99490000> 39200000 7d234b78 383f0040 > > The above can be interleaved with other messages and we'll still be able > to match process and its corresponding instruction dump. Yeah prefixing with the comm and pid is nice. Also the "Instruction dump:" line is a waste of space. I prefer the x86 format, where it's prefixed with "code:", eg: pandafault[10758]: segfault (11) at 00000000100007d0 nip 000000001000061c lr 00007fffabc85100 code 2 in pandafault[10000000+10000] pandafault[10758]: code: 4bfffeec 4bfffee8 3c401002 38427f00 fbe1fff8 f821ffc1 7c3f0b78 3d22fffe pandafault[10758]: code: 392988d0 f93f0020 e93f0020 39400048 <99490000> 39200000 7d234b78 383f0040 cheers