[PATCH 2.5] report unknown NMI reasons only once

[Pascal Schmidt]

Hi people!

On my machine (Athlon XP on an old ALi Magik1 motherboard), I get tons of
messages like:

Uhhuh. NMI received for unknown reason 2d on CPU 0.
Dazed and confused, but trying to continue
Do you have a strange power saving mode enabled?

There's nothing I can do about them (ACPI or APIC support in the kernel or
not does not make a difference, nor do any of the BIOS power management
settings). The machine runs fine, no problems in memtest86, and I've not
noticed a problem with a system in the three or four months that I'm
running this configuration.

Those NMIs happen only rarely when the machine is lightly loaded, but
under load, I get several of them per second. This quickly makes
/var/log/messages grow.

I don't think reporting any of those NMIs more than once provides
valuable information, so I've cooked up a patch which only reports each
unknown NMI reason once.

I don't know who the maintainer of arch/i386/kernel/traps.c is supposed
to be, so I'm sending this to the list and CC to Alan since he is not
unlikely to take small patches like this. ;)

Patch against 2.5.67-bk10. Compiles, boots and does what it's supposed to
do on my machine.

Comments, anyone?

--- linux-2.5.67-bk10/arch/i386/kernel/traps.c	Sat Apr 19 20:00:42 2003
+++ work/arch/i386/kernel/traps.c	Sat Apr 19 20:17:40 2003
@@ -5,6 +5,8 @@
  *
  *  Pentium III FXSR, SSE support
  *	Gareth Hughes <[e-mail]>, May 2000
+ *  Limit unknown NMI reporting
+ *     Pascal Schmidt <[e-mail]>, April 2003
  */
 
 /*
@@ -48,6 +50,8 @@
 #include <asm/pgalloc.h>
 #include <asm/arch_hooks.h>
 
+#include <asm/bitops.h>
+
 #include <linux/irq.h>
 #include <linux/module.h>
 
@@ -417,6 +421,9 @@ static void io_check_error(unsigned char
 	outb(reason, 0x61);
 }
 
+/* bit field for already reported unknown NMI reasons */
+static int unknown_nmi_reported[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
+
 static void unknown_nmi_error(unsigned char reason, struct pt_regs * regs)
 {
 #ifdef CONFIG_MCA
@@ -427,10 +434,13 @@ static void unknown_nmi_error(unsigned c
 		return;
 	}
 #endif
-	printk("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",
-		reason, smp_processor_id());
-	printk("Dazed and confused, but trying to continue\n");
-	printk("Do you have a strange power saving mode enabled?\n");
+	if ( !test_bit(reason, (void *)&unknown_nmi_reported) ) {
+		printk("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",
+			reason, smp_processor_id());
+		printk("Dazed and confused, but trying to continue\n");
+		printk("Do you have a strange power saving mode enabled?\n");
+		__set_bit(reason, (void *)&unknown_nmi_reported);
+	}
 }
 
 static void default_do_nmi(struct pt_regs * regs)

-- 
Ciao,
Pascal