Re: [PATCH] local_irq_disable removal

Sven-Thorsten Dietrich
2005-06-13T07:56:14Z

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.