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SubjectRe: Thoughts on this RCU idle entry/exit patch?
On Tue, Oct 08, 2013 at 02:12:18PM -0700, Paul E. McKenney wrote:
> On Tue, Oct 08, 2013 at 10:34:28PM +0200, Frederic Weisbecker wrote:
> > So I wonder, do we want to continue to allow this nesting? I remember that DYNTICK_TASK_NEST_*
> > stuff is there to protects against non finishing interrupts on some archs (I also remember that
> > this, or at least a practical scenario for this, was hard to really define though :o)
> > But then wouldn't it involve other kind of scenario like this?
> >
> > rcu_irq_enter()
> > rcu_eqs_enter()
> > rcu_eqs_exit()
> > ...
> >
> > Anyway, that's just random thougths on further simplifications, in any case, this
> > patch looks good.
>
> Yep, if no task-level nesting is ever required, things could be a bit
> simpler. I would be a bit slow about making such a change, though.
> After all, the need to deal with Hotel California interrupts means that
> handling nesting isn't that big of a deal comparatively. ;-)

Right, well ideally it would be even best to fix the corner case(s) if there aren't
that many of them. I mean calling rcu_irq_exit() from the end of those half interrupts
I guess. It would make it much simpler than this complicated nesting handled on the core code.
But I agree there is a bit of unknown out there, so yeah lets be prudent :)

> May I add your Reviewed-by?

Sure, thanks!


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