Messages in this thread | | | Date | Mon, 7 Aug 2023 11:23:44 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH v9 5/7] arm64: ipi_debug: Add support for backtrace using the debug IPI |
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On Thu, Jun 01, 2023 at 02:31:49PM -0700, Douglas Anderson wrote: > From: Sumit Garg <sumit.garg@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.garg@linaro.org> > Signed-off-by: Douglas Anderson <dianders@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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