Re: [PATCH] Avoid moving tasks when a schedule can be made.

[Ingo Molnar <mingo@elte.hu>]

* Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> >>So it is not a nice thing to tinker with unless there is good reason.
> >
> >unbound latencies with hardirqs off are obviously a good reason - but i 
> >agree that the solution is not good enough, yet.
> 
> Ah, so this is an RT tree thing where the scheduler lock turns off 
> "hard irqs"? [...]

no, this is about the mainline kernel turning off hardirqs for a long 
time. (i used the hardirqs-off terminology instead of irqs-off to 
differentiate it from softirqs-off a'ka local_bh_disable(). It's a 
side-effect of working on the lock validator i guess ;).

> [...] As opposed to something like the rwsem lock that only turns off 
> your "soft irqs" (sorry, I'm not with the terminlogy)?

rwsems/rwlocks are not an issue in -rt because they have different 
semantics there - and thus readers cannot amass. I do think rwsems and 
rwlocks have pretty nasty characteristics [non-latency ones] for the 
mainline kernel's use too, but that's not being argued here ;)

	Ingo