Subject: Re: Arches that don't support PREEMPT

On Tue, 2023-09-19 at 16:16 +0200, Peter Zijlstra wrote:
> > I find it a bit unfair that maintainers of architectures that have huge companies
> > behind them use their manpower to urge less popular architectures for removal just
> > because they don't have 150 people working on the port so they can keep up with
> > design changes quickly.
>
> PREEMPT isn't something new. Also, I don't think the arch part for
> actually supporting it is particularly hard, mostly it is sticking the
> preempt_schedule_irq() call in return from interrupt code path.
>
> If you convert the arch to generic-entry (a much larger undertaking)
> then you get this for free.

If the conversion isn't hard, why is the first reflex the urge to remove an architecture
instead of offering advise how to get the conversion done?

Adrian

--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer
`. `' Physicist
`- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913


2023-09-19 19:35:45

by Matthew Wilcox

[permalink] [raw]
Subject: Re: Arches that don't support PREEMPT

On Tue, Sep 19, 2023 at 04:24:48PM +0200, John Paul Adrian Glaubitz wrote:
> If the conversion isn't hard, why is the first reflex the urge to remove an architecture
> instead of offering advise how to get the conversion done?

Because PREEMPT has been around since before 2005 (cc19ca86a023 created
Kconfig.preempt and I don't need to go back further than that to make my
point), and you haven't done the work yet. Clearly it takes the threat
of removal to get some kind of motion.