linux-kernel - Re: [PATCH] x86: Avoid pr_cont() in show

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Date:   Wed, 11 Jul 2018 06:08:19 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     David Laight <David.Laight@...LAB.COM>,
        "'Josh Poimboeuf'" <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...e.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86: Avoid pr_cont() in show_opcodes()

On 2018/07/11 1:51, David Laight wrote:
> From: Josh Poimboeuf
>> Sent: 09 July 2018 20:12
>> On Mon, Jul 09, 2018 at 10:49:53AM +0200, Peter Zijlstra wrote:
>>> On Sat, Jul 07, 2018 at 10:54:28PM +0900, Tetsuo Handa wrote:
>>>>>> Since syzbot is confused by concurrent printk() messages [1],
>>>>>> this patch changes show_opcodes() to use snprintf().
>>>
>>> But how big of a problem is that really? We can't very well remove all
>>> pr_cont stuff from the kernel.
>>
>> I'd say we should try to make oopses as legible as possible.
> 
> To make oopses legible you need to lock the output between output lines.
> Which would require a 'KERN_CONTINUED' marker on the previous print.

There is an attempt to prefix context identifier to each line of output
( https://groups.google.com/d/msg/syzkaller/ttZehjXiHTU/JR67pXz3BAAJ ).
Therefore, I expect oops messages can stop using pr_cont()/KERN_CONT.