Re: [PATCH v7 4/7] nmi: backtrace: Allow runtime arch specific override

[Sumit Garg]

Hello arch maintainers,

On Mon, 2 Nov 2020 at 17:16, Sumit Garg <sumit.garg@xxxxxxxxxx> wrote:
>
> Add a boolean return to arch_trigger_cpumask_backtrace() to support a
> use-case where a particular architecture detects at runtime if it supports
> NMI backtrace or it would like to fallback to default implementation using
> SMP cross-calls.
>
> Currently such an architecture example is arm64 supporting pseudo NMIs
> feature which is only available on platforms which have support for GICv3
> or later version.
>
> Signed-off-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
> ---
>  arch/arm/include/asm/irq.h       |  2 +-
>  arch/arm/kernel/smp.c            |  3 ++-
>  arch/mips/include/asm/irq.h      |  2 +-
>  arch/mips/kernel/process.c       |  3 ++-
>  arch/powerpc/include/asm/nmi.h   |  2 +-
>  arch/powerpc/kernel/stacktrace.c |  3 ++-
>  arch/sparc/include/asm/irq_64.h  |  2 +-
>  arch/sparc/kernel/process_64.c   |  4 +++-
>  arch/x86/include/asm/irq.h       |  2 +-
>  arch/x86/kernel/apic/hw_nmi.c    |  3 ++-
>  include/linux/nmi.h              | 12 ++++--------
>  11 files changed, 20 insertions(+), 18 deletions(-)

Do you have any comments here? It would be nice to have your ack here.

-Sumit

>
> diff --git a/arch/arm/include/asm/irq.h b/arch/arm/include/asm/irq.h
> index 46d4114..54b0180 100644
> --- a/arch/arm/include/asm/irq.h
> +++ b/arch/arm/include/asm/irq.h
> @@ -31,7 +31,7 @@ void handle_IRQ(unsigned int, struct pt_regs *);
>  void init_IRQ(void);
>
>  #ifdef CONFIG_SMP
> -extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
> +extern bool arch_trigger_cpumask_backtrace(const cpumask_t *mask,
>                                            bool exclude_self);
>  #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
>  #endif
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 48099c6e..bb20a43 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -856,7 +856,8 @@ static void raise_nmi(cpumask_t *mask)
>         __ipi_send_mask(ipi_desc[IPI_CPU_BACKTRACE], mask);
>  }
>
> -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
> +bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
>  {
>         nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_nmi);
> +       return true;
>  }
> diff --git a/arch/mips/include/asm/irq.h b/arch/mips/include/asm/irq.h
> index c5d3517..34f3b42 100644
> --- a/arch/mips/include/asm/irq.h
> +++ b/arch/mips/include/asm/irq.h
> @@ -78,7 +78,7 @@ extern int cp0_fdc_irq;
>
>  extern int get_c0_fdc_int(void);
>
> -void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
> +bool arch_trigger_cpumask_backtrace(const struct cpumask *mask,
>                                     bool exclude_self);
>  #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
>
> diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
> index 75ebd8d..d19e672 100644
> --- a/arch/mips/kernel/process.c
> +++ b/arch/mips/kernel/process.c
> @@ -735,9 +735,10 @@ static void raise_backtrace(cpumask_t *mask)
>         }
>  }
>
> -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
> +bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
>  {
>         nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace);
> +       return true;
>  }
>
>  int mips_get_process_fp_mode(struct task_struct *task)
> diff --git a/arch/powerpc/include/asm/nmi.h b/arch/powerpc/include/asm/nmi.h
> index 84b4cfe..a5eb3e2 100644
> --- a/arch/powerpc/include/asm/nmi.h
> +++ b/arch/powerpc/include/asm/nmi.h
> @@ -9,7 +9,7 @@ static inline void arch_touch_nmi_watchdog(void) {}
>  #endif
>
>  #if defined(CONFIG_NMI_IPI) && defined(CONFIG_STACKTRACE)
> -extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
> +extern bool arch_trigger_cpumask_backtrace(const cpumask_t *mask,
>                                            bool exclude_self);
>  #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
>  #endif
> diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c
> index b644065..22b112a 100644
> --- a/arch/powerpc/kernel/stacktrace.c
> +++ b/arch/powerpc/kernel/stacktrace.c
> @@ -264,8 +264,9 @@ static void raise_backtrace_ipi(cpumask_t *mask)
>         }
>  }
>
> -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
> +bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
>  {
>         nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
> +       return true;
>  }
>  #endif /* defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) */
> diff --git a/arch/sparc/include/asm/irq_64.h b/arch/sparc/include/asm/irq_64.h
> index 4d748e9..35c01ff 100644
> --- a/arch/sparc/include/asm/irq_64.h
> +++ b/arch/sparc/include/asm/irq_64.h
> @@ -87,7 +87,7 @@ static inline unsigned long get_softint(void)
>         return retval;
>  }
>
> -void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
> +bool arch_trigger_cpumask_backtrace(const struct cpumask *mask,
>                                     bool exclude_self);
>  #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
>
> diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
> index a75093b..9182001 100644
> --- a/arch/sparc/kernel/process_64.c
> +++ b/arch/sparc/kernel/process_64.c
> @@ -248,7 +248,7 @@ static void __global_reg_poll(struct global_reg_snapshot *gp)
>         }
>  }
>
> -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
> +bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
>  {
>         struct thread_info *tp = current_thread_info();
>         struct pt_regs *regs = get_irq_regs();
> @@ -303,6 +303,8 @@ void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
>         memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));
>
>         spin_unlock_irqrestore(&global_cpu_snapshot_lock, flags);
> +
> +       return true;
>  }
>
>  #ifdef CONFIG_MAGIC_SYSRQ
> diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
> index 528c8a7..b7668e0 100644
> --- a/arch/x86/include/asm/irq.h
> +++ b/arch/x86/include/asm/irq.h
> @@ -47,7 +47,7 @@ extern void init_ISA_irqs(void);
>  extern void __init init_IRQ(void);
>
>  #ifdef CONFIG_X86_LOCAL_APIC
> -void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
> +bool arch_trigger_cpumask_backtrace(const struct cpumask *mask,
>                                     bool exclude_self);
>
>  #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
> diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
> index 34a992e..e7dcd28 100644
> --- a/arch/x86/kernel/apic/hw_nmi.c
> +++ b/arch/x86/kernel/apic/hw_nmi.c
> @@ -34,10 +34,11 @@ static void nmi_raise_cpu_backtrace(cpumask_t *mask)
>         apic->send_IPI_mask(mask, NMI_VECTOR);
>  }
>
> -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
> +bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
>  {
>         nmi_trigger_cpumask_backtrace(mask, exclude_self,
>                                       nmi_raise_cpu_backtrace);
> +       return true;
>  }
>
>  static int nmi_cpu_backtrace_handler(unsigned int cmd, struct pt_regs *regs)
> diff --git a/include/linux/nmi.h b/include/linux/nmi.h
> index 750c7f3..cedbfc1 100644
> --- a/include/linux/nmi.h
> +++ b/include/linux/nmi.h
> @@ -143,26 +143,22 @@ static inline void touch_nmi_watchdog(void)
>  #ifdef arch_trigger_cpumask_backtrace
>  static inline bool trigger_all_cpu_backtrace(void)
>  {
> -       arch_trigger_cpumask_backtrace(cpu_online_mask, false);
> -       return true;
> +       return arch_trigger_cpumask_backtrace(cpu_online_mask, false);
>  }
>
>  static inline bool trigger_allbutself_cpu_backtrace(void)
>  {
> -       arch_trigger_cpumask_backtrace(cpu_online_mask, true);
> -       return true;
> +       return arch_trigger_cpumask_backtrace(cpu_online_mask, true);
>  }
>
>  static inline bool trigger_cpumask_backtrace(struct cpumask *mask)
>  {
> -       arch_trigger_cpumask_backtrace(mask, false);
> -       return true;
> +       return arch_trigger_cpumask_backtrace(mask, false);
>  }
>
>  static inline bool trigger_single_cpu_backtrace(int cpu)
>  {
> -       arch_trigger_cpumask_backtrace(cpumask_of(cpu), false);
> -       return true;
> +       return arch_trigger_cpumask_backtrace(cpumask_of(cpu), false);
>  }
>
>  /* generic implementation */
> --
> 2.7.4
>