linux-kernel - Re: [PATCH v12 3/3] printk: make printk.synchronous param rw

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Date:	Sat, 23 Apr 2016 08:56:33 +0200
From:	Jan Kara <jack@...e.cz>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kara <jack@...e.com>, Petr Mladek <pmladek@...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>
Subject: Re: [PATCH v12 3/3] printk: make printk.synchronous param rw

On Fri 22-04-16 22:53:00, Sergey Senozhatsky wrote:
> Change `synchronous' printk param to be RW, so user space
> can change printk mode back and forth to/from sync mode
> (which is considered to be more reliable).
> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

The patch looks good to me. One suggestion below:

> @@ -1785,7 +1782,7 @@ asmlinkage int vprintk_emit(int facility, int level,
>  		 * operate in sync mode once panic() occurred.
>  		 */
>  		if (console_loglevel != CONSOLE_LOGLEVEL_MOTORMOUTH &&
> -				printk_kthread) {
> +				!printk_sync && printk_kthread) {
>  			/* Offload printing to a schedulable context. */
>  			printk_kthread_need_flush_console = true;
>  			wake_up_process(printk_kthread);

It would seem more future-proof to hide '!printk_sync && printk_kthread'
into a wrapper function as it is somewhat subtle detail that printk_kthread
needn't exist while !printk_sync and I can imagine someone forgetting to
check that in the future. Something like 'can_print_async()'? But I don't
feel too strongly about that so feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

regardless whether you change this or not.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR