Arches that don't support PREEMPT

[David Laight]

From: Linus Torvalds
> Sent: 19 September 2023 18:25
> 
> On Tue, 19 Sept 2023 at 06:48, John Paul Adrian Glaubitz
> <glaubitz at physik.fu-berlin.de> wrote:
> >
> > As Geert poined out, I'm not seeing anything particular problematic with the
> > architectures lacking CONFIG_PREEMPT at the moment. This seems to be more
> > something about organizing KConfig files.
> 
> It can definitely be problematic.
> 
> Not the Kconfig file part, and not the preempt count part itself.
> 
> But the fact that it has never been used and tested means that there
> might be tons of "this architecture code knows it's not preemptible,
> because this architecture doesn't support preemption".

Do distos even build x86 kernels with PREEMPT_FULL?
I know I've had issues with massive latencies caused graphics driver
forcing write-backs of all the framebuffer memory.
(I think it is a failed attempt to fix a temporary display corruption.)

OTOH SMP support and CONFIG_RT will test most of the code.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)