Re: [PATCH][2.5] fix for_each_cpu compilation on UP

From: Zwane Mwaikambo (
Date: Fri Jan 17 2003 - 11:44:34 EST

On Fri, 17 Jan 2003, James Bottomley wrote:

> said:
> > This adds a definition for for_each_cpu when !CONFIG_SMP
> > Please apply
> Could you elaborate on the purpose of this a bit? for_each_cpu() is only used
> by the voyager subarch on x86 to traverse sparse CPU bitmaps efficiently in
> critical path code. It has no other use in x86 SMP because all other
> subarch's tend to compact the CPU bitmap much more.
> If there are other uses for the construct, it should probably be put in bitops
> and become for_each_bit(i, mask)

It's still useful in the general case for avoiding access of per cpu
memory when a cpu is offline as well as avoiding triggering events on
cpus which aren't online anymore. I'm going to hold back on this for a bit
till i actually release the code which depends on this infrastructure.



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