Re: [RFC PATCH v3 10/16] sched: Core-wide rq->lock

[Vineeth Pillai]

>
> I'm confused, how doesn't this break the invariant above?
>
> That is, all CPUs must at all times agree on the value of rq_lockp(),
> and I'm not seeing how that is true with the above changes.
>
While fixing the crash in cpu online/offline, I was focusing on
maintaining the invariance
of all online cpus to agree on the value of rq_lockp(). Would it be
safe to assume that
rq and rq_lock would be used only after a cpu is onlined(sched:active)?.

To maintain the strict invariance, the sibling should also disable
core scheduling, but
we need to empty the rbtree before disabling it. I am trying to see
how to empty the
rbtree safely in the offline context.

Thanks,
Vineeth