On 2020-10-14 12:12, 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;
}
Can't you have *both* a request for a backtrace and a KGDB call?
It really shouldn't be either/or. It also outlines how well shared
interrupts work with edge triggered signalling...
M.
--
Jazz is not dead. It just smells funny...
