Re: [PATCH v4] cpuset: Enable cpuset controller in default hierarchy

[Mike Galbraith]

On Mon, 2018-03-19 at 08:34 -0700, Tejun Heo wrote:
> Hello, Mike.
> 
> On Thu, Mar 15, 2018 at 03:49:01AM +0100, Mike Galbraith wrote:
> > Under the hood v2 details are entirely up to you.  My input ends at
> > please don't leave dynamic partitioning standing at the dock when v2
> > sails.
> 
> So, this isn't about implementation details but about what the
> interface achieves - ie, what's the actual function?  The only thing I
> can see is blocking the entity which is configuring the hierarchy from
> making certain configs.  While that might be useful in some specific
> use cases, it seems to miss the bar for becoming its own kernel
> feature.  After all, nothing prevents the same entity from clearing
> the exlusive bit and making the said changes.

Yes, privileged contexts can maliciously or stupidly step all over one
other no matter what you do (finite resource), but oxymoron creation
(CPUs simultaneously balanced and isolated) should be handled.  If one
context can allocate a set overlapping a set another context intends to
or already has detached from scheduler domains, both are screwed.

	-Mike