From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754362Ab1KOBSH (ORCPT ); Mon, 14 Nov 2011 20:18:07 -0500 Received: from perches-mx.perches.com ([206.117.179.246]:45527 "EHLO labridge.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751891Ab1KOBSF (ORCPT ); Mon, 14 Nov 2011 20:18:05 -0500 Message-ID: <1321319883.8944.7.camel@Joe-Laptop> Subject: Re: Printk mulitple line message support From: Joe Perches To: Huang Ying Cc: William Douglas , Andrew Morton , "linux-kernel@vger.kernel.org" Date: Mon, 14 Nov 2011 17:18:03 -0800 In-Reply-To: <1321318201.13860.51.camel@yhuang-dev> References: <1321253936.13860.35.camel@yhuang-dev> <1321281640.2004.6.camel@Joe-Laptop> <1321318201.13860.51.camel@yhuang-dev> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.1- Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2011-11-15 at 08:50 +0800, Huang Ying wrote: > On Mon, 2011-11-14 at 22:40 +0800, Joe Perches wrote: > > On Mon, 2011-11-14 at 14:58 +0800, Huang Ying wrote: > > > Hi, > > > > > > In most cases, printk only guarantees messages from different printk > > > calling will not be interleaved between each other. But many printk > > > users uses multiple line to form a complete message and call printk > > > for each line. So the following situation is possible for two printk > > > users running on two CPUs. > > > > > > line 1 of message from printk user1 > > > line 1 of message from printk user2 > > > line 2 of message from printk user1 > > > line 2 of message from printk user2 > > > > > > This makes kernel log hard to read. One possible solution to this > > > issue is to give a sequence number (or ID) to each complete message. > > > So the above lines will be: > > > > > > {1}line 1 of message from printk user1 > > > {2}line 1 of message from printk user2 > > > {1}line 2 of message from printk user1 > > > {2}line 2 of message from printk user2 > > > > > > Then some simple script can be used to group lines together according > > > to sequence number in lines. > > > > > > What do you think about that? > > > > This makes the typical multi-part but non-interleaved > > output difficult to read. > > With a simple script, we can strip out the sequence # easily. > > > How about determining if there is interleaving and > > emitting sequence # only in those cases? > > > > Perhaps test the atomic for the last sequence #. > > So we will have no sequence # prefix for printk user1's lines if printk > user 2 comes in the middle? Something as follow? > > line 1 of message from printk user1 > {2}line 1 of message from printk user2 > line 2 of message from printk user1 > {2}line 2 of message from printk user2 > > This will make it hard for a script to sort the lines. Where should it > insert lines from printk user2 in the sort result? 90+% it's the previous line. I believe you are not solving any real problem with pr__ml. Most all interleaved complete line uses have some pr_fmt prefix that distinguishes between the sources. A perhaps larger problem is interleaved partial lines with pr_cont. I believe that an initiator/terminator is necessary for reassembly. Something that could be used with pr_, dev_, netdev_, et al. mp_start(&cookie) pr_(fmt, ...); pr_mp_cont(&cookie, fmt, ...); pr_mp_cont(&cookie, fmt "\n", ...); mp_end(&cookie);