Re: [PATCH] NMI trigger switch support for debugging

[AKIYAMA Nobuyuki <akiyama.nobuyuk@jp.fujitsu.com>]

Hi Andrew,

Andrew Morton wrote:

> Great, thanks. Updates to Documentation/kernel-parameters.txt and
> Documentation/filesystems/proc.txt would be nice.
>

I wrote a document(proc.txt), and remade a patch that merged Mikael and
Andi's feedback.
The patch has been tested well.

Regards,
Nobuyuki Akiyama


--- proc.txt.orig	2004-05-27 14:28:38.000000000 +0900
+++ proc.txt	2004-05-27 14:28:07.000000000 +0900
@@ -1105,6 +1105,20 @@
 The location  where  the  modprobe  binary  is  located.  The kernel uses this
 program to load modules on demand.
 
+unknown_nmi_panic
+-----------------
+
+The value in this file affects behavior of handling NMI. When the value is
+non-zero, unknown NMI is trapped and then panic occurs. At that time, kernel
+debugging information is displayed on console.
+
+NMI switch that most IA32 servers have fires unknown NMI up, for example.
+If a system hangs up, try pressing the NMI switch.
+
+[NOTE]
+   This function and oprofile share a NMI callback. Therefore this function
+   cannot be enabled when oprofile is activated.
+
 2.4 /proc/sys/vm - The virtual memory subsystem
 -----------------------------------------------
 
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;
 
 /*
  * 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 }
 };