Re: suspend blockers & Android integration

[Ingo Molnar]

* Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Fri, 4 Jun 2010, Ingo Molnar wrote:
> > 
> >    This allows a task to 'exclude' other tasks that dont have low-latency 
> >    requirements. Crappy apps would have a large latency value, so they'd
> >    be idled out when a privileged task sets the exclusion level low enough.
> 
> Quite frankly, this sounds fundamentally broken.
>
> Think deadlock. The high-latency task got a lock, and now you're excluding 
> it because it scheduled away.

Mail was a bit too long already so i trimmed it at the wrong place :-/

What you say is absolutely true, hence this would be driven via sched_tick() + 
TIF notifiers - i.e. only ever treat user-mode tasks as 'idle-able'. This can 
be done with no overhead to the regular fastpaths.

The TIF notifier would be the one scheduling to idle - and would thus do it 
only to user-mode tasks.

Thanks,

	Ingo
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