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SubjectRe: [PATCH] include/log2.h: Fix rounddown_pow_of_two(1)
On Mon, 14 Nov 2011, Andrei Warkentin wrote:

> ----- Original Message -----
> > From: "Jesper Juhl" <jj@chaosbits.net>
> > To: "Andrei Warkentin" <andreiw@vmware.com>
> > Cc: linux-kernel@vger.kernel.org
> > Sent: Tuesday, November 8, 2011 2:57:27 PM
> > Subject: Re: [PATCH] include/log2.h: Fix rounddown_pow_of_two(1)
> >
> > On Tue, 8 Nov 2011, Andrei Warkentin wrote:
> >
> > > 1 is a power of two, therefore rounddown_pow_of_two(1) should
> > > return 1. It does
> > > in case the argument is a variable but in case it's a constant it
> > > behaves
> > > wrong and returns 0. Probably nobody ever did it so this was never
> > > noticed,
> > > however net/drivers/vmxnet3 with latest GCC does and breaks on
> > > unicpu systems.
> > >
> > > Signed-off-by: Andrei Warkentin <andreiw@vmware.com>
> > > ---
> > > include/linux/log2.h | 2 +-
> > > 1 files changed, 1 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/include/linux/log2.h b/include/linux/log2.h
> > > index 25b8086..ccda848 100644
> > > --- a/include/linux/log2.h
> > > +++ b/include/linux/log2.h
> > > @@ -185,7 +185,7 @@ unsigned long __rounddown_pow_of_two(unsigned
> > > long n)
> > > #define rounddown_pow_of_two(n) \
> > > ( \
> > > __builtin_constant_p(n) ? ( \
> > > - (n == 1) ? 0 : \
> > > + (n == 1) ? 1 : \
> > > (1UL << ilog2(n))) : \
> > > __rounddown_pow_of_two(n) \
> > > )
> > >
> >
> > For what it's worth; looks good to me.
>
> Is that an Acked-by or a Reviewed-by?
>
I don't really know (to be honest). I guess it is whichever is weakest,
since I did review the patch and convinced myself that the change was
sane, but didn't spent a whole lot of time checking that *all* users were
OK with it...


--
Jesper Juhl <jj@chaosbits.net> http://www.chaosbits.net/
Don't top-post http://www.catb.org/jargon/html/T/top-post.html
Plain text mails only, please.



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