linux-kernel - Re: [PATCH] printk: stop spining waiter when console resume to flush prb

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Message-ID: <YJkhsb7h5Ptn+oFO@google.com>
Date:   Mon, 10 May 2021 21:06:09 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Petr Mladek <pmladek@...e.com>
Cc:     luojiaxing <luojiaxing@...wei.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        john.ogness@...utronix.de, linux-kernel@...r.kernel.org,
        linuxarm@...wei.com, bobo.shaobowang@...wei.com
Subject: Re: [PATCH] printk: stop spining waiter when console resume to flush
 prb

On (21/05/10 11:50), Petr Mladek wrote:
[..]
> The only problem is that it becomes the console_owner too late.
> It spends long time by flushing the accumulated messages. But
> they are its own messages after all.
> 
> The only real solution is to pass the console work to a separate
> kthread and do not block any printk() caller.

Yeah, but even that thing is getting complex fairly quickly.
wake_up_process() queues kthread on the same CPU, so if the
printk() (ab)-user is in atomic context then printing kthread
won't get scheduled.