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SubjectRe: [PATCH v2] arm64: run softirqs on the per-CPU IRQ stack
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On 2022/8/2 14:53, 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@bytedance.com>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Acked-by: Will Deacon <will@kernel.org>

Hi Will,

Are we good to merge it into 6.0-rc1?

Thanks,
Qi

> ---
> v1: https://lore.kernel.org/lkml/20220708094950.41944-1-zhengqi.arch@bytedance.com/
> RFC: https://lore.kernel.org/lkml/20220707110511.52129-1-zhengqi.arch@bytedance.com/
>
> 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 1652a9800ebe..90f1ab403724 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -226,6 +226,7 @@ config ARM64
> select THREAD_INFO_IN_TASK
> select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD
> select TRACE_IRQFLAGS_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

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