[PATCH 6/6 V2] x86, nmi: Add better NMI stats to /proc/interrupts and show handlers

Don Zickus
2014-05-15T19:28:06Z

The main reason for this patch is because I have a hard time knowing
what NMI handlers are registered on the system when debugging NMI issues.

This info is provided in /proc/interrupts for interrupt handlers, so I
added support for NMI stuff too. As a bonus it provides stat breakdowns
much like the interrupts.

[root@dhcp71-248 ~]# cat /proc/interrupts
CPU0 CPU1 CPU2 CPU3
0: 32 0 0 0 IR-IO-APIC-edge timer
<snip>
NMI: 13 15 7 6 Non-maskable interrupts
NLC: 12 13 8 7 NMI: Local (PMI, arch_bt)
NXT: 0 0 0 0 NMI: External (plat)
NUN: 0 0 0 0 NMI: Unknown
NSW: 0 0 0 0 NMI: Swallowed
LOC: 23768 18248 14187 15891 Local timer interrupts
SPU: 0 0 0 0 Spurious interrupts
PMI: 11 12 7 6 Performance monitoring interrupts
IWI: 2131 1196 862 1113 IRQ work interrupts

The extra 'local' NMI count represents the number of NMIs 'handled'
whereas the general NMI count represents how many actual NMIs were
processed. IOW, two NMIs came in at once during one call.

I am open to better suggestions.

Signed-off-by: Don Zickus <dzickus@redhat.com>
---
V2: modified output based on feedback (Ingo Molnar, Rob Elliott)
---
arch/x86/include/asm/nmi.h | 1 +
arch/x86/kernel/irq.c | 3 ++
arch/x86/kernel/nmi.c | 57 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 61 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/nmi.h b/arch/x86/include/asm/nmi.h
index c8ffab3..cbb49a2 100644
--- a/arch/x86/include/asm/nmi.h
+++ b/arch/x86/include/asm/nmi.h
@@ -63,6 +63,7 @@ void unregister_nmi_handler(unsigned int, const char *);
void stop_nmi(void);
void restart_nmi(void);
void local_touch_nmi(void);
+void nmi_show_interrupts(struct seq_file *, int);

int register_nmi_default_external_handler(void);
void unregister_nmi_default_external_handler(void);
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 42805fa..a969f87 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -17,6 +17,7 @@
#include <asm/idle.h>
#include <asm/mce.h>
#include <asm/hw_irq.h>
+#include <asm/nmi.h>

#define CREATE_TRACE_POINTS
#include <asm/trace/irq_vectors.h>
@@ -59,6 +60,8 @@ int arch_show_interrupts(struct seq_file *p, int prec)
for_each_online_cpu(j)
seq_printf(p, "%10u ", irq_stats(j)->__nmi_count);
seq_printf(p, " Non-maskable interrupts\n");
+ nmi_show_interrupts(p, prec);
+
#ifdef CONFIG_X86_LOCAL_APIC
seq_printf(p, "%*s: ", prec, "LOC");
for_each_online_cpu(j)
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 458be2a..f54fea3 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -506,6 +506,63 @@ static __kprobes void default_do_nmi(struct pt_regs *regs)
unknown_nmi_error(regs);
}

+static void print_nmi_action_name(struct seq_file *p, int type)
+{
+ struct nmi_desc *desc;
+ struct nmiaction *a;
+
+ rcu_read_lock();
+
+ desc = nmi_to_desc(type);
+
+ if (!(list_empty(&desc->head))) {
+
+ a = list_entry_rcu(desc->head.next, struct nmiaction, list);
+ seq_printf(p, " (%s", a->name);
+
+ list_for_each_entry_continue_rcu(a, &desc->head, list)
+ seq_printf(p, ", %s", a->name);
+
+ seq_printf(p, ")");
+ }
+ seq_puts(p, "\n");
+
+ rcu_read_unlock();
+}
+
+void nmi_show_interrupts(struct seq_file *p, int prec)
+{
+ int j;
+
+#define get_nmi_stats(j) (&per_cpu(nmi_stats, j))
+
+ seq_printf(p, "%*s: ", prec, "NLC");
+ for_each_online_cpu(j)
+ seq_printf(p, "%10u ", get_nmi_stats(j)->normal);
+ seq_printf(p, " %-8s", " NMI: Local");
+
+ print_nmi_action_name(p, NMI_LOCAL);
+
+ seq_printf(p, "%*s: ", prec, "NXT");
+ for_each_online_cpu(j)
+ seq_printf(p, "%10u ", get_nmi_stats(j)->external);
+ seq_printf(p, " %-8s", " NMI: External");
+
+ print_nmi_action_name(p, NMI_EXT);
+
+ seq_printf(p, "%*s: ", prec, "NUN");
+ for_each_online_cpu(j)
+ seq_printf(p, "%10u ", get_nmi_stats(j)->unknown);
+ seq_printf(p, " %-8s", " NMI: Unknown");
+
+ print_nmi_action_name(p, NMI_UNKNOWN);
+
+ seq_printf(p, "%*s: ", prec, "NSW");
+ for_each_online_cpu(j)
+ seq_printf(p, "%10u ", get_nmi_stats(j)->swallow);
+ seq_printf(p, " %-8s", " NMI: Swallowed\n");
+}
+
/*
* Prevent NMI reason port (0x61) being accessed simultaneously, can
* only be used in NMI handler.
--
1.7.1