linux-kernel - Re: [RFC][PATCH v9 1/2] printk: Make printk() completely async

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Message-ID: <20160401163917.GC1212@swordfish>
Date:	Sat, 2 Apr 2016 01:39:17 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Petr Mladek <pmladek@...e.com>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kara <jack@...e.com>, Tejun Heo <tj@...nel.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	linux-kernel@...r.kernel.org,
	Byungchul Park <byungchul.park@....com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Jan Kara <jack@...e.cz>
Subject: Re: [RFC][PATCH v9 1/2] printk: Make printk() completely async

On (04/01/16 17:00), Petr Mladek wrote:
> You need to move this assigment right above the console_lock()/console_unlock()
> calls. Otherwise, there is a race:
> 
> CPU0:				CPU1
> 
> printk_kthread_func()
> 
>   console_unlock()
> 
> 				printk()
> 
> 				printk_kthread_need_flush_console = true;
> 				wake_up_process(printk_kthread);
> 
>   printk_kthread_need_flush_console = false;
> 
>   set_current_state(TASK_INTERRUPTIBLE);
>   if (!printk_kthread_need_flush_console)
>     schedule();

thanks. yeah, this can add latency to some messages.

	-ss