[PATCH 0/10] use safer test on the result of find_first_zero_bit

Geert Uytterhoeven geert at linux-m68k.org
Wed Jun 4 04:07:34 PDT 2014

Hi Julia,

On Wed, Jun 4, 2014 at 1:00 PM, Julia Lawall <julia.lawall at lip6.fr> wrote:
> OK, thanks.  I was only looking at the C code.
> But the C code contains a loop that is followed by:
>         if (!size)
>                 return result;
>         tmp = *p;
> found_first:
>         tmp |= ~0UL << size;
>         if (tmp == ~0UL)        /* Are any bits zero? */
>                 return result + size;   /* Nope. */
> In the first return, it would seem that result == size.  Could the second
> one be changed to just return size?  It should not hurt performance.

"size" may have been changed between function entry and this line.
So you have to store it in a temporary.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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