linux-kernel - Re: [PATCH] Avoid time

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Date:	Sat, 24 Mar 2007 06:20:45 +0100 (CET)
From:	Roman Zippel <zippel@...ux-m68k.org>
To:	john stultz <johnstul@...ibm.com>
cc:	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Avoid time_offset overflows

Hi,

On Fri, 23 Mar 2007, john stultz wrote:

> @@ -314,8 +314,8 @@ #endif
>  		    freq_adj += time_freq;
>  		    freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
>  		    time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
> -		    time_offset = (time_offset / NTP_INTERVAL_FREQ)
> -		    			<< SHIFT_UPDATE;
> +		    do_div(time_offset, NTP_INTERVAL_FREQ);
> +		    time_offset <<= SHIFT_UPDATE;
>  		} /* STA_PLL */
>  	    } /* txc->modes & ADJ_OFFSET */
>  	    if (txc->modes & ADJ_TICK)

This is wrong, time_offset is signed and do_div is unsigned.
In general I planned to do the same change, but the do_div API could use a 
little cleanup to provide some clear function for signed/unsigned divide 
(hopefully with a better name than div_long_long_rem_signed or 
do_div_llr).

bye, Roman
-
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