Re: [PATCH] NMI trigger switch support for debugging

From: AKIYAMA Nobuyuki
Date: Tue May 25 2004 - 20:37:55 EST

Hi Andrew,

Andrew Morton wrote:

AKIYAMA Nobuyuki <akiyama.nobuyuk@xxxxxxxxxxxxxx> 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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