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SubjectRe: [PATCH 2/2] sched: fix cpupri priocount
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On Wed, 2008-06-04 at 15:04 -0400, Gregory Haskins wrote:
> A rounding error was pointed out by Peter Zijlstra which would result
> in the structure holding priorities to be off by one.
>
> Signed-off-by: Gregory Haskins <ghaskins@novell.com>
> CC: Peter Zijlstra <peterz@infradead.org>
> ---
>
> kernel/sched_cpupri.h | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/sched_cpupri.h b/kernel/sched_cpupri.h
> index 16d29b9..817c55c 100644
> --- a/kernel/sched_cpupri.h
> +++ b/kernel/sched_cpupri.h
> @@ -4,7 +4,7 @@
> #include <linux/sched.h>
>
> #define CPUPRI_NR_PRIORITIES 2+MAX_RT_PRIO
> -#define CPUPRI_NR_PRI_WORDS CPUPRI_NR_PRIORITIES/BITS_PER_LONG
> +#define CPUPRI_NR_PRI_WORDS (CPUPRI_NR_PRIORITIES + BITS_PER_LONG/2)/BITS_PER_LONG

(33 + 16) / 32 = 49 / 32 = 1

So its still wrong ;-)

Please use DECLARE_BITMAP and or BITS_TO_LONGS to avoid these issues.



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