[PATCH 0/10] use safer test on the result of find_first_zero_bit
julia.lawall at lip6.fr
Wed Jun 4 04:00:07 PDT 2014
On Wed, 4 Jun 2014, Geert Uytterhoeven wrote:
> Hi Julia,
> On Wed, Jun 4, 2014 at 11:52 AM, Julia Lawall <julia.lawall at lip6.fr> wrote:
> >> Maybe the documented return code should be changed to allow for the
> >> existing behaviour.
> > Sorry, I'm not sure to understand what you suggest here.
> | /**
> | * find_first_zero_bit - find the first cleared bit in a memory region
> | * @addr: The address to start the search at
> | * @size: The maximum number of bits to search
> | *
> | * Returns the bit number of the first cleared bit.
> | * If no bits are zero, returns @size.
> "If no bits are zero, returns @size or a number larger than @size."
OK, thanks. I was only looking at the C code.
But the C code contains a loop that is followed by:
tmp = *p;
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.
> | */
> | extern unsigned long find_first_zero_bit(const unsigned long *addr,
> | unsigned long size);
> 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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