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Date: Tue, 8 Nov 2011 20:57:27 +0100 (CET) From: Jesper Juhl <jj@...osbits.net> To: Andrei Warkentin <andreiw@...are.com> cc: linux-kernel@...r.kernel.org 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@...are.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. -- Jesper Juhl <jj@...osbits.net> http://www.chaosbits.net/ Don't top-post http://www.catb.org/jargon/html/T/top-post.html Plain text mails only, please. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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