linux-kernel - Re: [PATCH] watchdog: using u64 in get_sample

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Date:	Wed, 21 Nov 2012 08:57:49 -0500
From:	Don Zickus <dzickus@...hat.com>
To:	Chuansheng Liu <chuansheng.liu@...el.com>
Cc:	akpm@...ux-foundation.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog: using u64 in get_sample_period()

On Wed, Nov 21, 2012 at 06:56:07PM +0800, Chuansheng Liu wrote:
> 
> In get_sample_period(), unsigned long is not enough:
> watchdog_thresh * 2 * (NSEC_PER_SEC / 5)
> 
> case1: watchdog_thresh is 10 by default,
> the sample value will be: 0xEE6B 2800
> 
> case2: set watchdog_thresh is 20,
> the sample value will be: 0x1 DCD6 5000
> 
> >From case2, we need use u64 to express the sample period.
> Otherwise, Changing the threshold thru proc often can
> not be successful.

I guess I should have tested 32-bit more. :-) Good catch.

Acked-by: Don Zickus <dzickus@...hat.com>

> 
> Signed-off-by: liu chuansheng <chuansheng.liu@...el.com>
> ---
>  kernel/watchdog.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 9d4c8d5..dd4b80a 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -116,7 +116,7 @@ static unsigned long get_timestamp(int this_cpu)
>  	return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
>  }
>  
> -static unsigned long get_sample_period(void)
> +static u64 get_sample_period(void)
>  {
>  	/*
>  	 * convert watchdog_thresh from seconds to ns
> @@ -125,7 +125,7 @@ static unsigned long get_sample_period(void)
>  	 * and hard thresholds) to increment before the
>  	 * hardlockup detector generates a warning
>  	 */
> -	return get_softlockup_thresh() * (NSEC_PER_SEC / 5);
> +	return get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
>  }
>  
>  /* Commands for resetting the watchdog */
> -- 
> 1.7.0.4
> 
> 
> 
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