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 19B44C43381 for ; Thu, 21 Mar 2019 03:00:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E3AB920811 for ; Thu, 21 Mar 2019 02:59:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727857AbfCUC76 (ORCPT ); Wed, 20 Mar 2019 22:59:58 -0400 Received: from ozlabs.org ([203.11.71.1]:55507 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726983AbfCUC76 (ORCPT ); Wed, 20 Mar 2019 22:59:58 -0400 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 44Ps2y6Fmjz9sR4; Thu, 21 Mar 2019 13:59:54 +1100 (AEDT) From: Michael Ellerman To: Tetsuo Handa , Petr Mladek , Sergey Senozhatsky Cc: Dmitry Vyukov , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Andrew Morton , LKML , syzkaller Subject: Re: [PATCH] printk: Add caller information to printk() output. In-Reply-To: <93f19e57-5051-c67d-9af4-b17624062d44@i-love.sakura.ne.jp> References: <20181203150603.cdqii263e4kmmibo@pathway.suse.cz> <20181204152724.ypk44mi4a56nrud4@pathway.suse.cz> <459018db-763b-9520-ead2-2c0d5975fbf3@i-love.sakura.ne.jp> <20181210130930.bas4fozjhe3dc5nu@pathway.suse.cz> <20181213121847.mwlr2vyv6qzclhk6@pathway.suse.cz> <20181213124255.GB3053@tigerII.localdomain> <20181217145452.3kev4rmo2l5lt2qy@pathway.suse.cz> <93f19e57-5051-c67d-9af4-b17624062d44@i-love.sakura.ne.jp> Date: Thu, 21 Mar 2019 13:59:53 +1100 Message-ID: <871s312aqe.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 Hi Tetsuo, Thanks for implementing this, it's really helpful. Tetsuo Handa writes: ... > From 91f85d2bd494df2f73c605d8b4747e8cc0a61ae2 Mon Sep 17 00:00:00 2001 > From: Tetsuo Handa > Date: Tue, 18 Dec 2018 05:53:04 +0900 > Subject: [PATCH] printk: Add caller information to printk() output. > > Sometimes we want to print a series of printk() messages to consoles > without being disturbed by concurrent printk() from interrupts and/or > other threads. But we can't enforce printk() callers to use their local > buffers because we need to ask them to make too much changes. Also, even > buffering up to one line inside printk() might cause failing to emit > an important clue under critical situation. > > Therefore, instead of trying to help buffering, let's try to help > reconstructing messages by saving caller information as of calling > log_store() and adding it as "[T$thread_id]" or "[C$processor_id]" > upon printing to consoles. > > Some examples for console output: > > [ 1.222773][ T1] x86: Booting SMP configuration: > [ 2.779635][ T1] pci 0000:00:01.0: PCI bridge to [bus 01] > [ 5.069193][ T268] Fusion MPT base driver 3.04.20 > [ 9.316504][ C2] random: fast init done > [ 13.413336][ T3355] Initialized host personality > > Some examples for /dev/kmsg output: > > 6,496,1222773,-,caller=T1;x86: Booting SMP configuration: > 6,968,2779635,-,caller=T1;pci 0000:00:01.0: PCI bridge to [bus 01] > SUBSYSTEM=pci > DEVICE=+pci:0000:00:01.0 > 6,1353,5069193,-,caller=T268;Fusion MPT base driver 3.04.20 > 5,1526,9316504,-,caller=C2;random: fast init done > 6,1575,13413336,-,caller=T3355;Initialized host personality > > Note that this patch changes max length of messages which can be printed > by printk() or written to /dev/kmsg interface from 992 bytes to 976 bytes, > based on an assumption that userspace won't try to write messages hitting > that border line to /dev/kmsg interface. Do you have any plans to update dmesg or other userspace tools to show the caller information? cheers