Re: [PATCH 06/13] cpuset: cleanup cpuset[_can]_attach()

From: Rusty Russell
Date: Wed Jan 02 2013 - 20:17:15 EST

Tejun Heo <tj@xxxxxxxxxx> writes:
> Hello, Rusty.
> On Wed, Jan 02, 2013 at 03:12:15PM +1030, Rusty Russell wrote:
>> > Hmmm? cpumask_t can't be used for stack but other than that I don't
>> > see how it would be deprecated completely. Rusty, can you please
>> > chime in?
>> The long-never-quite-complete-plan was for struct cpumask to be
>> undefined when CONFIG_CPUMASK_OFFSTACK=y. That means noone can declare
>> them, or pass them on the stack, since they'll get a compiler error.
>> Now, there are some cases where it really is a reason to use a static
>> bitmap, and 1/2 a K of wasted space be damned. There's a
>> deliberately-ugly way of doing that: declare a bitmap and use
>> to_cpumask(). Of course, if we ever really want to remove NR_CPUS and
>> make it completely generic, we have to kill all these too, but noone is
>> serious about that.
> So, I guess this currently is caught in a place which isn't here or
> there. I'm pretty skeptical whether it makes sense to bother about
> static usages tho. Can I keep them for static ones?

I didn't realize that cpuset_attach was a fastpath. If it is, put a
static there and I'll fix turn it into a bitmap when I need to.
Otherwise, please don't change the code in the first place.

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