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

[Qi Zheng]

On 2022/7/7 20:58, Arnd Bergmann wrote:
> On Thu, Jul 7, 2022 at 1:05 PM Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> wrote:
> > Currently arm64 supports per-CPU IRQ stack, but softirqs
> > are still handled in the task context.
> >
> > Since any call to local_bh_enable() at any level in the task's
> > call stack may trigger a softirq processing run, which could
> > potentially cause a task stack overflow if the combined stack
> > footprints exceed the stack's size, let's run these softirqs
> > on the IRQ stack as well.
> >
> > Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
>
> I think this is the correct approach, but your patch conflicts with another
> patch I have queued up in the asm-generic tree, see
> https://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git/commit/?h=asm-generic&id=f2c5092190f21
>
> Please adapt accordingly.

OK, will do in the next version.

> 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.

Thanks,
Qi

>          Arnd

--
Thanks,
Qi