Messages in this thread | | | Date | Tue, 15 Nov 2011 00:27:00 +0100 (CET) | From | Jesper Juhl <> | Subject | Re: [PATCH] include/log2.h: Fix rounddown_pow_of_two(1) |
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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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