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Date: Mon, 23 Mar 2009 15:39:07 +1100
From: Paul Mackerras <paulus@samba.org>
To: davidastro <davidastro@hotmail.com>
Subject: Re: Fix for __div64_32 locks when using some 64 bit numbers
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davidastro <davidastro@hotmail.com> writes:

> Basically, the numbers shown above was causing the 64 by 32 bit algorithm to
> divide by zero making the unit spin and also giving incorrect results.
> Here is the code as it was before.
[snip]
>         cntlzw  r0,r5           # we are shifting the dividend right
>         li      r10,-1          # to make it < 2^32, and shifting
>         srw     r10,r10,r0      # the divisor right the same amount,
>         add     r9,r4,r10       # rounding up (so the estimate cannot
>         andc    r11,r6,r10      # ever be too large, only too small)
>         andc    r9,r9,r10      #THIS CODE COULD STORE A ZERO IN r9
>         or      r11,r5,r11
>         rotlw   r9,r9,r0
>         rotlw   r11,r11,r0

That bug was fixed in October 2005 in commit 344480b99730bfd2, and the
fix is in v2.6.15-rc1 and all later kernels.  I fixed it a bit
differently to your suggestion though - see

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=344480b99730bfd205e306d3fd168cdcebe83425

You must be working from an old kernel tree - which kernel version are
you using?

Paul.