linux-kernel - Re: Would you help to tell why async printk solution was not taken to upstream kernel ?

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Date:   Mon, 05 Mar 2018 14:56:59 +0800
From:   "Qixuan.Wu" <qixuan.wu@...ux.alibaba.com>
To:     "Steven Rostedt" <rostedt@...dmis.org>
Cc:     "linux-kernel-owner" <linux-kernel-owner@...r.kernel.org>,
        "Petr Mladek" <pmladek@...e.com>, "Jan Kara" <jack@...e.cz>,
        "Sergey Senozhatsky" <sergey.senozhatsky@...il.com>,
        "Sergey Senozhatsky" <sergey.senozhatsky.work@...il.com>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        "chenggang.qin" <chenggang.qin@...ux.alibaba.com>,
        "caijingxian" <caijingxian@...ux.alibaba.com>,
        "yuanliang.wyl" <yuanliang.wyl@...baba-inc.com>
Subject: Re: Would you help to tell why async printk solution was not taken to upstream kernel ?

Hi Steve,  

On Sun, 04 Mar 2018 23:43:23 +0800
Steven Rostedt <rostedt@...dmis.org> wrote:

> Yes, people keep bringing up this scenario.
> It would require a single burst of printks to all CPUs. And then no
> more printks after that. The last one will end up printing the entire
> buffer out the slow console. The thing is, this is a bounded time, and
> no printk will print more than one full buffer worth.

> If this is a worry, then set the timeouts for the lockup detection to
> be longer than the time it takes to print one full buffer with the
> slowest console.

Thanks for your information and suggestion. We will think of backport 
the code as per the workload, or recently, maybe we will think of disable 
ttyS0 console just for the printk. 

Thanks & Regards
Qixuan