Re: [PATCH v3] arm64: run softirqs on the per-CPU IRQ stack

[Qi Zheng]

On 2022/8/26 12:16, Qi Zheng wrote:
> On 2022/8/15 20:47, Qi Zheng 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>
> > Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>
> > Acked-by: Will Deacon <will@xxxxxxxxxx>
> > ---
> > v2: 
> > https://lore.kernel.org/lkml/20220802065325.39740-1-zhengqi.arch@xxxxxxxxxxxxx/
> > v1: 
> > https://lore.kernel.org/lkml/20220708094950.41944-1-zhengqi.arch@xxxxxxxxxxxxx/
> > RFC: 
> > https://lore.kernel.org/lkml/20220707110511.52129-1-zhengqi.arch@xxxxxxxxxxxxx/
> >
> > Changelog in v2 -> v3:
> >   - rebase onto the v6.0-rc1

Hi Will,

Are we good to merge this patch? Or if there is anything else I need to
do, please let me know. :)

Looking forward to your reply.

Thanks,
Qi

> Gentle ping.
>
> Thanks,
> Qi
>
> > Changelog in v1 -> v2:
> >   - temporarily discard [PATCH v1 2/2] to allow this patch to be 
> > merged first
> >   - rebase onto the v5.19
> >   - collect Reviewed-by and Acked-by
> >
> > Changelog in RFC -> v1:
> >   - fix conflicts with commit f2c5092190f2 ("arch/*: Disable softirq 
> > stacks on PREEMPT_RT.")
> >
> >   arch/arm64/Kconfig      |  1 +
> >   arch/arm64/kernel/irq.c | 13 +++++++++++++
> >   2 files changed, 14 insertions(+)
> >
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index 571cc234d0b3..ee92f5887cf6 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -230,6 +230,7 @@ config ARM64
> >       select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD
> >       select TRACE_IRQFLAGS_SUPPORT
> >       select TRACE_IRQFLAGS_NMI_SUPPORT
> > +    select HAVE_SOFTIRQ_ON_OWN_STACK
> >       help
> >         ARM 64-bit (AArch64) Linux support.
> > diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
> > index bda49430c9ea..c36ad20a52f3 100644
> > --- a/arch/arm64/kernel/irq.c
> > +++ b/arch/arm64/kernel/irq.c
> > @@ -22,6 +22,7 @@
> >   #include <linux/vmalloc.h>
> >   #include <asm/daifflags.h>
> >   #include <asm/vmap_stack.h>
> > +#include <asm/exception.h>
> >   /* Only access this in an NMI enter/exit */
> >   DEFINE_PER_CPU(struct nmi_ctx, nmi_contexts);
> > @@ -71,6 +72,18 @@ static void init_irq_stacks(void)
> >   }
> >   #endif
> > +#ifndef CONFIG_PREEMPT_RT
> > +static void ____do_softirq(struct pt_regs *regs)
> > +{
> > +    __do_softirq();
> > +}
> > +
> > +void do_softirq_own_stack(void)
> > +{
> > +    call_on_irq_stack(NULL, ____do_softirq);
> > +}
> > +#endif
> > +
> >   static void default_handle_irq(struct pt_regs *regs)
> >   {
> >       panic("IRQ taken without a root IRQ handler\n");

--
Thanks,
Qi