Re: [PATCH 05/32] nohz: Move rcu dynticks idle mode handling to idle enter/exit APIs

Frederic Weisbecker
2011-08-29T17:12:06Z

On Mon, Aug 29, 2011 at 04:25:22PM +0200, Peter Zijlstra wrote:
> On Mon, 2011-08-15 at 17:52 +0200, Frederic Weisbecker wrote:
> > To prepare for nohz / idle logic split, pull out the rcu dynticks
> > idle mode switching to strict idle entry/exit areas.
> >
> > So we make the dyntick mode possible without always involving rcu
> > extended quiescent state.
>
> Why is this a good thing? I would be thinking that if we're a userspace
> bound task and we disable the tick rcu would be finished on this cpu and
> thus the extended quiescent state is just what we want?

But we can stop the tick from the kernel, not just userspace.