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SubjectRe: [PATCH] NMI trigger switch support for debugging
Hi Andrew,

Andrew Morton wrote:

>AKIYAMA Nobuyuki <akiyama.nobuyuk@jp.fujitsu.com> wrote:
>
>
>>Therefore this feature cannot be used at the same time with oprofile
>> and NMI watchdog. This feature hands NMI interrupt over to oprofile
>> and NMI watchdog. So, when they have been activated, this feature
>> doesn't work even if it is activated.
>>
>>
>
>An API was recently added to solve this. See reserve_lapic_nmi() and
>release_lapic_nmi().
>
>
>

Thank you for your comment.
I remade my patch referring to your suggestion.

Regards,
Nobuyuki Akiyama


diff -Nur linux-2.6.6.org/arch/i386/kernel/nmi.c
linux-2.6.6/arch/i386/kernel/nmi.c
--- linux-2.6.6.org/arch/i386/kernel/nmi.c 2004-05-25
20:02:45.000000000 +0900
+++ linux-2.6.6/arch/i386/kernel/nmi.c 2004-05-26 09:48:23.000000000
+0900
@@ -25,16 +25,20 @@
#include <linux/module.h>
#include <linux/nmi.h>
#include <linux/sysdev.h>
+#include <linux/sysctl.h>

#include <asm/smp.h>
#include <asm/mtrr.h>
#include <asm/mpspec.h>
#include <asm/nmi.h>

+#include "mach_traps.h"
+
unsigned int nmi_watchdog = NMI_NONE;
static unsigned int nmi_hz = HZ;
unsigned int nmi_perfctr_msr; /* the MSR to reset in NMI handler */
extern void show_registers(struct pt_regs *regs);
+int unknown_nmi_panic = 0;

/*
* lapic_nmi_owner tracks the ownership of the lapic NMI hardware:
@@ -419,8 +423,6 @@
nmi_active = 1;
}

-static spinlock_t nmi_print_lock = SPIN_LOCK_UNLOCKED;
-
/*
* the best way to detect whether a CPU has a 'hard lockup' problem
* is to check it's local APIC timer IRQ counts. If they are not
@@ -452,6 +454,8 @@
alert_counter[i] = 0;
}

+extern void die_nmi(struct pt_regs *, const char *msg);
+
void nmi_watchdog_tick (struct pt_regs * regs)
{

@@ -470,21 +474,8 @@
* wait a few IRQs (5 seconds) before doing the oops ...
*/
alert_counter[cpu]++;
- if (alert_counter[cpu] == 5*nmi_hz) {
- spin_lock(&nmi_print_lock);
- /*
- * We are in trouble anyway, lets at least try
- * to get a message out.
- */
- bust_spinlocks(1);
- printk("NMI Watchdog detected LOCKUP on CPU%d, eip %08lx,
registers:\n", cpu, regs->eip);
- show_registers(regs);
- printk("console shuts up ...\n");
- console_silent();
- spin_unlock(&nmi_print_lock);
- bust_spinlocks(0);
- do_exit(SIGSEGV);
- }
+ if (alert_counter[cpu] == 5*nmi_hz)
+ die_nmi(regs, "NMI Watchdog detected LOCKUP");
} else {
last_irq_sums[cpu] = sum;
alert_counter[cpu] = 0;
@@ -511,6 +502,45 @@
}
}

+static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
+{
+ unsigned char reason = get_nmi_reason();
+ char buf[64];
+
+ if (!(reason & 0xc0)) {
+ sprintf(buf, "NMI received for unknown reason %02x\n", reason);
+ die_nmi(regs, buf);
+ }
+ return 0;
+}
+
+/*
+ * proc handler for /proc/sys/kernel/unknown_nmi_panic
+ */
+int proc_unknown_nmi_panic(ctl_table *table, int write,
+ struct file *file, void __user *buffer, size_t *length)
+{
+ int old_state;
+
+ old_state = unknown_nmi_panic;
+ proc_dointvec(table, write, file, buffer, length);
+ if (!old_state == !unknown_nmi_panic)
+ return 0;
+
+ if (unknown_nmi_panic) {
+ if (reserve_lapic_nmi() < 0) {
+ unknown_nmi_panic = 0;
+ return -EBUSY;
+ } else {
+ set_nmi_callback(unknown_nmi_panic_callback);
+ }
+ } else {
+ release_lapic_nmi();
+ unset_nmi_callback();
+ }
+ return 0;
+}
+
EXPORT_SYMBOL(nmi_active);
EXPORT_SYMBOL(nmi_watchdog);
EXPORT_SYMBOL(reserve_lapic_nmi);
diff -Nur linux-2.6.6.org/arch/i386/kernel/traps.c
linux-2.6.6/arch/i386/kernel/traps.c
--- linux-2.6.6.org/arch/i386/kernel/traps.c 2004-05-25
20:02:45.000000000 +0900
+++ linux-2.6.6/arch/i386/kernel/traps.c 2004-05-25
22:54:03.000000000 +0900
@@ -454,6 +454,27 @@
printk("Do you have a strange power saving mode enabled?\n");
}

+static spinlock_t nmi_print_lock = SPIN_LOCK_UNLOCKED;
+
+void die_nmi (struct pt_regs *regs, const char *msg)
+{
+ spin_lock(&nmi_print_lock);
+ /*
+ * We are in trouble anyway, lets at least try
+ * to get a message out.
+ */
+ bust_spinlocks(1);
+ printk(msg);
+ printk(" on CPU%d, eip %08lx, registers:\n",
+ smp_processor_id(), regs->eip);
+ show_registers(regs);
+ printk("console shuts up ...\n");
+ console_silent();
+ spin_unlock(&nmi_print_lock);
+ bust_spinlocks(0);
+ do_exit(SIGSEGV);
+}
+
static void default_do_nmi(struct pt_regs * regs)
{
unsigned char reason = get_nmi_reason();
diff -Nur linux-2.6.6.org/include/linux/sysctl.h
linux-2.6.6/include/linux/sysctl.h
--- linux-2.6.6.org/include/linux/sysctl.h 2004-05-25
20:03:13.000000000 +0900
+++ linux-2.6.6/include/linux/sysctl.h 2004-05-25 22:54:03.000000000
+0900
@@ -133,6 +133,7 @@
KERN_NGROUPS_MAX=63, /* int: NGROUPS_MAX */
KERN_SPARC_SCONS_PWROFF=64, /* int: serial console power-off halt */
KERN_HZ_TIMER=65, /* int: hz timer on or off */
+ KERN_UNKNOWN_NMI_PANIC=66, /* int: unknown nmi panic flag */
};


diff -Nur linux-2.6.6.org/kernel/sysctl.c linux-2.6.6/kernel/sysctl.c
--- linux-2.6.6.org/kernel/sysctl.c 2004-05-25 20:03:31.000000000 +0900
+++ linux-2.6.6/kernel/sysctl.c 2004-05-25 22:54:03.000000000 +0900
@@ -65,6 +65,12 @@
extern int printk_ratelimit_jiffies;
extern int printk_ratelimit_burst;

+#if defined(__i386__)
+extern int unknown_nmi_panic;
+extern int proc_unknown_nmi_panic(ctl_table *, int, struct file *,
+ void __user *, size_t *);
+#endif
+
/* this is needed for the proc_dointvec_minmax for [fs_]overflow UID
and GID */
static int maxolduid = 65535;
static int minolduid;
@@ -636,6 +642,16 @@
.mode = 0444,
.proc_handler = &proc_dointvec,
},
+#if defined(__i386__)
+ {
+ .ctl_name = KERN_UNKNOWN_NMI_PANIC,
+ .procname = "unknown_nmi_panic",
+ .data = &unknown_nmi_panic,
+ .maxlen = sizeof (int),
+ .mode = 0644,
+ .proc_handler = &proc_unknown_nmi_panic,
+ },
+#endif
{ .ctl_name = 0 }
};



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