Paul Jackson wrote:
> From: Paul Jackson <pj@sgi.com>
> 
> Remove the cpuset hooks that defined sched domains depending on the
> setting of the 'cpu_exclusive' flag.

Before we chuck the baby out...

> The cpu_exclusive flag can only be set on a child if it is set on
> the parent.
> 
> This made that flag painfully unsuitable for use as a flag defining
> a partitioning of a system.

Sigh, it isn't. That's simply how cpusets tried to use it.

> It was entirely unobvious to a cpuset user what partitioning of sched
> domains they would be causing when they set that one cpu_exclusive bit
> on one cpuset, because it depended on what CPUs were in the remainder
> of that cpusets siblings and child cpusets, after subtracting out
> other cpu_exclusive cpusets.

As far as a user is concerned, the cpusets is the interface. domain
partitioning is an implementation detail that just happens to make
it work better in some cases.

> Furthermore, there was no way on production systems to query the
> result.

You shouldn't need to, assuming cpusets doesn't mess it up.

Here is an untested patch. Apparently takes care of CPU hotplug too.

-- 
SUSE Labs, Novell Inc.