linux-kernel - Re: [PATCH] printk: git rid of [sched_delayed] message for printk

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Message-ID: <20140924113553.075e5bb1@gandalf.local.home>
Date:	Wed, 24 Sep 2014 11:35:53 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Jan Kara <jack@...e.cz>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] printk: git rid of [sched_delayed] message for
 printk_deferred

Andrew,

You want to pull this patch?

Thanks,

-- Steve


On Wed, 24 Sep 2014 17:20:19 +0200
Markus Trippelsdorf <markus@...ppelsdorf.de> wrote:

> commit 458df9fd hardcodes printk_deferred() to KERN_WARNING and inserts
> the string "[sched_delayed] " before the actual message.
> However it doesn't take into account the KERN_* prefix of the message,
> that now ends up in the middle of the output:
> 
>  [sched_delayed] ^a4CE: hpet increased min_delta_ns to 20115 nsec
> 
> Fix this by just getting rid of the "[sched_delayed] " scnprintf(). The
> prefix is useless since commit 458df9fd4815 (printk: remove separate
> printk_sched buffers and use printk buf instead) anyway since from that
> moment printk_deferred() inserts the message into the kernel printk buffer
> immediately. So if the message eventually gets printed to console, it is
> printed in the correct order with other messages and there's no need for
> any special prefix. And if the kernel crashes before the message makes it
> to console, then prefix in the printk buffer doesn't make the situation any
> better.
> 
> Link: http://lkml.org/lkml/2014/9/14/4
> 
> Acked-by: Jan Kara <jack@...e.cz>
> Acked-by: Steven Rostedt <rostedt@...dmis.org> 
> Signed-off-by: Markus Trippelsdorf <markus@...ppelsdorf.de>
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 1ce770687ea8..f85994b58934 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1680,12 +1680,7 @@ asmlinkage int vprintk_emit(int facility, int level,
>  	 * The printf needs to come first; we need the syslog
>  	 * prefix which might be passed-in as a parameter.
>  	 */
> -	if (in_sched)
> -		text_len = scnprintf(text, sizeof(textbuf),
> -				     KERN_WARNING "[sched_delayed] ");
> -
> -	text_len += vscnprintf(text + text_len,
> -			       sizeof(textbuf) - text_len, fmt, args);
> +	text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
>  
>  	/* mark and strip a trailing newline */
>  	if (text_len && text[text_len-1] == '\n') {

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