From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758231Ab3LXEyX (ORCPT ); Mon, 23 Dec 2013 23:54:23 -0500 Received: from mail4.hitachi.co.jp ([133.145.228.5]:50024 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752976Ab3LXEyV (ORCPT ); Mon, 23 Dec 2013 23:54:21 -0500 X-AuditID: 85900ec0-d3b2cb9000001514-cd-52b9137958f3 Message-ID: <52B91374.9000307@hitachi.com> Date: Tue, 24 Dec 2013 13:54:12 +0900 From: Yoshihiro YUNOMAE User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120604 Thunderbird/13.0 MIME-Version: 1.0 To: Kay Sievers Cc: LKML , Eiichi Tsukata , Frederic Weisbecker , Tejun Heo , yrl.pp-manager.tt@hitachi.com, Masami Hiramatsu , Joe Perches , Andrew Morton , Hidehiro Kawai Subject: Re: Re: Re: [PATCH 0/2] [BUGFIX] printk: Fix message continuation breakage involved with structured printk References: <20131220094134.24233.2969.stgit@yunodevel> <52B8F678.2090604@hitachi.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2013/12/24 12:00), Kay Sievers wrote: > On Tue, Dec 24, 2013 at 3:50 AM, Yoshihiro YUNOMAE > wrote: >> (2013/12/20 20:29), Kay Sievers wrote: >>> >>> On Fri, Dec 20, 2013 at 10:41 AM, Yoshihiro YUNOMAE >>> wrote: >>> >>>> This patch set fixes message continuation breakage involved with >>>> structured >>>> printk. A SCSI driver may output two continuation error messages like >>>> scmd_printk("foo"); >>>> printf("bar\n"); >>> >>> >>> Which is the absolutely wrong thing to do. Structured logging and racy >>> printk continuation must never be mixed. Userspace needs to be sure >>> that dictionary entries are not subject to racy continuation hackery, >>> and that these mwssages atomic, whole and intact. >> >> >> I see. >> As you say, user tools need to support messages output in multiple lines >> for SMP environments even if this patch set is introduced. > > They cannot really, they can try to re-construct, but Information and > context is sometimes lost with the use of continuation lines. > Structured logging need to be reliable and trustable, and it it is not > "best effort", hence it cannot use continuation lines. > > Continuation lines are a nice debugging tool for humans only. > Structured logging carries the human readable string but also > machine-readable context and that alwasy needs to be safely > machine-readable and recognizable. I understand. I think if we make machine(user tools) handle important messages, those messages need to be output in single line even if those are not structured printk. >>> Please do not mix the both and do not apply these patches. >> >> OK, I'll make important messages with KERN_CONT or no-prefix printk() >> output those in single line. > > Yes, it should use the plain printk versions and not the one which add > structured data. > > If structured logging is really wanted for more complex continuation > lines, it might be the simplest to buffer the line locally, instead of > the single printk-owned buffer, before the line is emitted to printk. Yes, I'll do that. Thanks, Yoshihiro YUNOMAE -- Yoshihiro YUNOMAE Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: yoshihiro.yunomae.ez@hitachi.com