On Thu, Jun 01, 2023 at 02:31:49PM -0700, Douglas Anderson wrote:
> From: Sumit Garg <sumit.g...@linaro.org>
>
> Enable arch_trigger_cpumask_backtrace() support on arm64 using the new
> debug IPI. With this arm64 can now get backtraces in cases where
> callers of the trigger_xyz_backtrace() class of functions don't check
> the return code and implement a fallback. One example is
> `kernel.softlockup_all_cpu_backtrace`. This also allows us to
> backtrace hard locked up CPUs in cases where the debug IPI is backed
> by an NMI (or pseudo NMI).
>
> Signed-off-by: Sumit Garg <sumit.g...@linaro.org>
> Signed-off-by: Douglas Anderson <diand...@chromium.org>
> ---
>
> Changes in v9:
> - Added comments that we might not be using NMI always.
> - Renamed "NMI IPI" to "debug IPI" since it might not be backed by NMI.
> - arch_trigger_cpumask_backtrace() no longer returns bool
>
> Changes in v8:
> - Removed "#ifdef CONFIG_SMP" since arm64 is always SMP
>
> arch/arm64/include/asm/irq.h | 3 +++
> arch/arm64/kernel/ipi_debug.c | 25 +++++++++++++++++++++++--
> 2 files changed, 26 insertions(+), 2 deletions(-)
As with prior patches, I'd prefer if this lived in smp.c with the other IPI
logic.
>
> diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
> index fac08e18bcd5..be2d103f316e 100644
> --- a/arch/arm64/include/asm/irq.h
> +++ b/arch/arm64/include/asm/irq.h
> @@ -6,6 +6,9 @@
>
> #include <asm-generic/irq.h>
>
> +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool
> exclude_self);
> +#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
> +
> struct pt_regs;
>
> int set_handle_irq(void (*handle_irq)(struct pt_regs *));
> diff --git a/arch/arm64/kernel/ipi_debug.c b/arch/arm64/kernel/ipi_debug.c
> index b57833e31eaf..6984ed507e1f 100644
> --- a/arch/arm64/kernel/ipi_debug.c
> +++ b/arch/arm64/kernel/ipi_debug.c
> @@ -8,6 +8,7 @@
>
> #include <linux/interrupt.h>
> #include <linux/irq.h>
> +#include <linux/nmi.h>
> #include <linux/smp.h>
>
> #include "ipi_debug.h"
> @@ -24,11 +25,31 @@ void arm64_debug_ipi(cpumask_t *mask)
> __ipi_send_mask(ipi_debug_desc, mask);
> }
>
> +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
> +{
> + /*
> + * NOTE: though nmi_trigger_cpumask_backtrace has "nmi_" in the name,
> + * nothing about it truly needs to be backed by an NMI, it's just that
> + * it's _allowed_ to be called from an NMI. If set_smp_debug_ipi()
> + * failed to get an NMI (or pseudo-NMI) this will just be backed by a
> + * regular IPI.
> + */
> + nmi_trigger_cpumask_backtrace(mask, exclude_self, arm64_debug_ipi);
> +}
> +
> static irqreturn_t ipi_debug_handler(int irq, void *data)
> {
> - /* nop, NMI handlers for special features can be added here. */
> + irqreturn_t ret = IRQ_NONE;
> +
> + /*
> + * NOTE: Just like in arch_trigger_cpumask_backtrace(), we're calling
> + * a function with "nmi_" in the name but it works fine even if we
> + * are using a regulaor IPI.
> + */
> + if (nmi_cpu_backtrace(get_irq_regs()))
> + ret = IRQ_HANDLED;
>
Does this need the printk_deferred_{enter,exit}() that 32-bit arm has?
Thanks,
Mark.
> - return IRQ_NONE;
> + return ret;
> }
>
> void debug_ipi_setup(void)
> --
> 2.41.0.rc2.161.g9c6817b8e7-goog
>
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