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SubjectRe: [PATCH 1/2] Make x86_64 udelay() round up instead of down.
Hi!

> From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
>
> Port two patches from i386 to x86_64 delay.c to make sure all rounding is done
> upward instead of downward.
>
> There is no sign in commit messages that the mismatch was done on purpose, and
> "delay() guarantees sleeping at least for the specified time" is still a valid
> rule IMHO.

> diff --git a/arch/x86_64/lib/delay.c b/arch/x86_64/lib/delay.c
> index 50be909..7514df0 100644
> --- a/arch/x86_64/lib/delay.c
> +++ b/arch/x86_64/lib/delay.c
> @@ -40,13 +40,13 @@ EXPORT_SYMBOL(__delay);
>
> inline void __const_udelay(unsigned long xloops)
> {
> - __delay((xloops * HZ * cpu_data[raw_smp_processor_id()].loops_per_jiffy) >> 32);
> + __delay((xloops * HZ * cpu_data[raw_smp_processor_id()].loops_per_jiffy) >> 32 + 1);

Well, if this should be *rounding* up, you should do

(xloops * HZ * cpu_data[raw_smp_processor_id()].loops_per_jiffy + 0xffffffff) >> 32

, no? Not sure if it matters...

Pavel
--
(english) http://www.livejournal.com/~pavelmachek
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