On Wed, Oct 14, 2020 at 04:42:11PM +0530, Sumit Garg wrote:
> Enable NMI backtrace support on arm64 using IPI turned as an NMI
> leveraging pseudo NMIs support. It is now possible for users to get a
> backtrace of a CPU stuck in hard-lockup using magic SYSRQ.
>
> Signed-off-by: Sumit Garg <sumit.g...@linaro.org>
> ---
> arch/arm64/include/asm/irq.h | 6 ++++++
> arch/arm64/kernel/ipi_nmi.c | 12 +++++++++++-
> 2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
> index b2b0c64..e840bf1 100644
> --- a/arch/arm64/include/asm/irq.h
> +++ b/arch/arm64/include/asm/irq.h
> @@ -6,6 +6,12 @@
>
> #include <asm-generic/irq.h>
>
> +#ifdef CONFIG_SMP
> +extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
> + bool exclude_self);
> +#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
> +#endif
> +
> struct pt_regs;
>
> static inline int nr_legacy_irqs(void)
> diff --git a/arch/arm64/kernel/ipi_nmi.c b/arch/arm64/kernel/ipi_nmi.c
> index e0a9e03..e1dc19d 100644
> --- a/arch/arm64/kernel/ipi_nmi.c
> +++ b/arch/arm64/kernel/ipi_nmi.c
> @@ -9,6 +9,7 @@
> #include <linux/interrupt.h>
> #include <linux/irq.h>
> #include <linux/kgdb.h>
> +#include <linux/nmi.h>
> #include <linux/smp.h>
>
> #include <asm/nmi.h>
> @@ -25,12 +26,21 @@ void arch_send_call_nmi_func_ipi_mask(cpumask_t *mask)
> __ipi_send_mask(ipi_desc, mask);
> }
>
> +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
> +{
> + nmi_trigger_cpumask_backtrace(mask, exclude_self,
> + arch_send_call_nmi_func_ipi_mask);
> +}
> +
> static irqreturn_t ipi_nmi_handler(int irq, void *data)
> {
> unsigned int cpu = smp_processor_id();
>
> - ipi_kgdb_nmicallback(cpu, get_irq_regs());
> + if (nmi_cpu_backtrace(get_irq_regs()))
> + goto out;
>
> + ipi_kgdb_nmicallback(cpu, get_irq_regs());
> +out:
> return IRQ_HANDLED;
> }
>
> --
It works well. Please feel free to add:
Tested-by: Masayoshi Mizuma <m.miz...@jp.fujitsu.com>
Thanks!
Masa
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