Re: [PATCH] local_irq_disable removal

[Sven-Thorsten Dietrich <sdietrich@mvista.com>]

On Mon, 2005-06-13 at 09:44 +0200, Esben Nielsen wrote:
> On Mon, 13 Jun 2005, Sven-Thorsten Dietrich wrote:
> 
> > On Sat, 2005-06-11 at 22:03 +0200, Ingo Molnar wrote:
> > > * Esben Nielsen <simlo@phys.au.dk> wrote:
> > > 
> > > > > the jury is still out on the accuracy of those numbers. The test had 
> > > > > RT_DEADLOCK_DETECT (and other -RT debugging features) turned on, which 
> > > > > mostly work with interrupts disabled. The other question is how were 
> > > > > interrupt response times measured.
> > > > > 
> > > > You would accept a patch where I made this stuff optional?
> > > 
> > > I'm not sure why. The soft-flag based local_irq_disable() should in fact 
> > > be a tiny bit faster than the cli based approach, on a fair number of 
> > > CPUs. But it should definitely not be slower in any measurable way.
> > > 
> > 
> > Is there any such SMP concept as a local_preempt_disable()  ?
> > 
> You must think of preempt_disable() ? Except for the interface is a little
> bit different using flags in local_irq_save(), preempt_disable() works
> exactly the same way, blocking for everything but interrupts - on the
> _local_ CPU. (Under PREEMPT_RT it ofcourse also blocks for threaded IRQ
> handlers.)

Doesn't preempt_disable() also block rescheduling on other CPUs?

We only need to prevent rescheduling on THIS CPU.



-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/