Re: [RFC PATCH 1/2] arm64: run softirqs on the per-CPU IRQ stack

[Qi Zheng]

On 2022/7/7 21:53, Arnd Bergmann wrote:
> On Thu, Jul 7, 2022 at 3:43 PM Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> wrote:
> > On 2022/7/7 20:58, Arnd Bergmann wrote:
> > > On Thu, Jul 7, 2022 at 1:05 PM Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> wrote:
> > > Are there any architectures left that use IRQ stacks but don't
> > > set HAVE_SOFTIRQ_ON_OWN_STACK? If not, we could
> > > also consider removing the Kconfig symbol and just requiring
> > > it to be done this way (for non-PREEMPT_RT).
> >
> > I haven't taken a close look at other architectures than x86 and arm,
> > but I think it's a good idea.
>
> I had another look in the meantime, and I think it's only mips and loongarch
> now that don't use HAVE_SOFTIRQ_ON_OWN_STACK. Not sure about
> arch/um/, which is a bit different from the rest.

I just glanced at arch/um/, and it's really different from the rest:

 * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
 * and switch over to the IRQ stack after some preparation.

>         Arnd

--
Thanks,
Qi