linux-kernel - Re: [uml-devel] BUG: soft lockup for a user mode linux image

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Date:	Fri, 11 Oct 2013 16:12:55 +0200
From:	Toralf Förster <toralf.foerster@....de>
To:	Fengguang Wu <fengguang.wu@...el.com>
CC:	Richard Weinberger <richard@....at>, Jan Kara <jack@...e.cz>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	UML devel <user-mode-linux-devel@...ts.sourceforge.net>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	hannes@...xchg.org, darrick.wong@...cle.com,
	Michal Hocko <mhocko@...e.cz>
Subject: Re: [uml-devel] BUG: soft lockup for a user mode linux image

On 10/11/2013 10:57 AM, Fengguang Wu wrote:
> On Fri, Oct 11, 2013 at 10:42:19AM +0200, Toralf Förster wrote:
>> yeah, now the picture becomes more clear
>> ...
>> net.core.warnings = 0                                                                         [ ok ]
>> ick: pause : -717
>>                  ick : min_pause : -177
>>                                    ick : max_pause : -717
>>                                                      ick: pages_dirtied : 14
>>                                                                             ick: task_ratelimit: 0
> 
> Great and thanks! So it's the max pause calculation went wrong.
> Would help you try the below patch?
> 
Definitely.
I'm running now the test case since 6 hours w/o any issues.
before that usually after 15 - 30 min the bug occurred.

>>>From 5420b9bbe42dd0a366d7615e9f3d3724cee725c4 Mon Sep 17 00:00:00 2001
> From: Fengguang Wu <fengguang.wu@...el.com>
> Date: Fri, 11 Oct 2013 16:53:26 +0800
> Subject: [PATCH] fix bdi max pause calculation
> 
> Signed-off-by: Fengguang Wu <fengguang.wu@...el.com>
> ---
>  mm/page-writeback.c |   10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 3f0c895..241a746 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1104,11 +1104,11 @@ static unsigned long dirty_poll_interval(unsigned long dirty,
>  	return 1;
>  }
>  
> -static long bdi_max_pause(struct backing_dev_info *bdi,
> -			  unsigned long bdi_dirty)
> +static unsigned long bdi_max_pause(struct backing_dev_info *bdi,
> +				   unsigned long bdi_dirty)
>  {
> -	long bw = bdi->avg_write_bandwidth;
> -	long t;
> +	unsigned long bw = bdi->avg_write_bandwidth;
> +	unsigned long t;
>  
>  	/*
>  	 * Limit pause time for small memory systems. If sleeping for too long
> @@ -1120,7 +1120,7 @@ static long bdi_max_pause(struct backing_dev_info *bdi,
>  	t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8));
>  	t++;
>  
> -	return min_t(long, t, MAX_PAUSE);
> +	return min_t(unsigned long, t, MAX_PAUSE);
>  }
>  
>  static long bdi_min_pause(struct backing_dev_info *bdi,
> 


-- 
MfG/Sincerely
Toralf Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3
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