Re: [PATCH 2/3] Dynamic sched domains (v0.6)

[Dinakar Guniguntala <dino@in.ibm.com>]

On Tue, May 17, 2005 at 04:25:37PM +1000, Nick Piggin wrote:
> >+
> >+	lock_cpu_hotplug();
> >+	partition_sched_domains(&pspan, &cspan);
> >+	unlock_cpu_hotplug();
> >+}
> >+
> 
> I don't think the cpu hotplug lock isn't supposed to provide
> synchronisation between readers (for example, it may be turned
> into an rwsem), but only between the thread and the cpu hotplug
> callbacks.

That should be ok

> 
> In that case, can you move this locking into kernel/sched.c, and
> add the comment in partition_sched_domains that the callers must
> take care of synchronisation (which without reading the code, I
> assume you're doing with the cpuset sem?).

I didnt want to do this as my next patch, which introduces
hotplug support for dynamic sched domains, also calls 
partition_sched_domains. That code is called with the hotplug lock
already held. (I am still testing that code, it should be out by 
this weekend)

However I will add a comment about the synchronization and yes
currently it is taken care of by the cpuset sem

	-Dinakar