Re: RT patch acceptance

Ingo Molnar
2005-06-01T19:40:44Z

* Andrea Arcangeli <andrea@suse.de> wrote:

> > So if PREEMPT-RT would use a soft cli/sti emulation, no problem should
> > arise.
>
> So I wonder why it doesn't do that and it leaves local_irq_disable
> uncovered [...]
>
> Perhaps that's planned and not yet implemented?

yes. As i said in an earlier mail:

> > (there are still some ways to introduce latencies into PREEMPT_RT,
> > but they are not common and we are working on ways to cover them
> > all.)

local_irq_disable() is one way, preempt_disable() is another way. Adding
asm("cli") to your driver is a third way. In practice these items are
not a big issue, so i'm not yet covering them. It's a small detail.
Check the amount of local-irq-disable instances in the driver space vs.
spinlock use.

Ingo