re: P6 bug?!

Trevor Johnson (trevor@jpj.net)
Thu, 10 Apr 1997 02:30:28 -0700 (PDT)


Chris Dee wrote:

> Could somebody please tell me what this means:
>
> Ignoring P6 Local APIC Spurious Interrupt Bug...
>
> Is there a problem with the P6? Or with the board? If it's a problem with
> the P6, do all P6's have this problem? Does this bug affect the system in
> any way?

See the bottom of this message for an explanation.

> Is it a problem to comment out the line in the kernel that shows this
> message? It's messing up the display.

Since the bug is ignored, giving debugging priority to the message seems
justified. Here's a trivial patch (against 2.1.32) to do that.

--- linux/arch/i386/kernel/traps.c.orig Sat Apr 5 14:46:43 1997
+++ linux/arch/i386/kernel/traps.c Thu Apr 10 02:15:24 1997
@@ -316,7 +316,7 @@
asmlinkage void do_spurious_interrupt_bug(struct pt_regs * regs,
long error_code)
{
- printk("Ignoring P6 Local APIC Spurious Interrupt Bug...\n");
+ printk(KERN_DEBUG "Ignoring P6 Local APIC Spurious Interrupt Bug...\n");
}

/*

___
Trevor Johnson <trevor@jpj.net>

>From lnz@dandelion.com Thu Apr 10 02:11:07 1997
Date: Sun, 17 Nov 1996 09:25:54 -0800
From: "Leonard N. Zubkoff" <lnz@dandelion.com>
To: Rob.Hagopian@vuser.vu.union.edu
Cc: linux-kernel@vger.rutgers.edu
Subject: Re: Strange P6 2.0.25 syslog message

From: Rob Hagopian <Rob.Hagopian@vuser.vu.union.edu>
Date: Sun, 17 Nov 1996 04:49:59 -0500 (EST)

> > This message showed up in my syslog today. I am running 2.0.25 SMP/ Dual
> > Pro 200. Any idea what it means?
> >
> > Nov 16 19:29:44 newton kernel: Ignoring P6 Local APIC Spurious Interrupt Bug...
>
> It means the kernel worked around a subtle and erratic bug in the Intel P6
> chip.

Is this bug found in all known steppings?
-Rob

I believe so. Last I checked, my stepping 7 P6-200's were still the latest.

Leonard

>From lnz@dandelion.com Thu Apr 10 02:11:14 1997
Date: Sun, 17 Nov 1996 09:38:09 -0800
From: "Leonard N. Zubkoff" <lnz@dandelion.com>
To: boozer@vanadium.rollins.edu
Cc: linux-kernel@vger.rutgers.edu
Subject: Re: Strange P6 2.0.25 syslog message

Date: Sun, 17 Nov 1996 01:01:06 -0500 (EST)
From: Chris Griffin <boozer@vanadium.rollins.edu>

This message showed up in my syslog today. I am running 2.0.25 SMP/ Dual
Pro 200. Any idea what it means?

Nov 16 19:29:44 newton kernel: Ignoring P6 Local APIC Spurious Interrupt Bug...

I wrote the patch... The P6 CPU has a bug whereby a spurious interrupt may be
delivered as an exception 15 trap rather than an interrupt 15. Spurious
interrupts are a normal part of system operation and occur from time to time.
The above message means that one of these exception 15 traps occurred. Had the
new handler not been in place, you'd either have received a "reserved" trap
message if you were running in the kernel, or the running user process would
have received a SEGV without further comment. This latter case was
particularly insidious, since it makes your system look flakey or like it has
bad memory.

Leonard