On Tue, 13 Nov 2007 11:22:45 -0800 David Brownell <[email protected]> wrote:
> On Tuesday 13 November 2007, Ingo Molnar wrote:
> >
> > * David Brownell <[email protected]> wrote:
> >
> > > > > I speculate that either the design has changed (without fanfare),
> > > > > or else that stuff is in RT kernels and has not yet gone upstream.
> > > >
> > > > Well whatever. We shouldn't have to resort to caller-side party
> > > > tricks like this to get acceptable performance.
> > >
> > > I'd be happy if, as originally presented, it were possible to just
> > > pass a raw_spinlock_t to spin_lock_irqsave() and friends.
> >
> > that's a spinlock type abstraction of PREEMPT_RT, not of mainline.
>
> Any reason that stuff shouldn't move into mainline?
>
>
> > Why do you want to use raw_spinlock_t?
>
> Already answered elsewhere in this thread ...
Can't say I really understood the answer. I don't think we actually know
where all of this extra time is being spent?
> I'll highlight the
> point that such bitops shouldn't be preemption points.
Disagree. *everything* should be a preemption point. For
internal-implementation details we do need to disable preemtion sometimes
(to prevent deadlocks and to protect per-cpu resources). But those
preemption-off periods should be minimised.
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