linux-kernel - Re: Math-emu kills the kernel on Athlon64 X2

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Message-ID: <Pine.LNX.4.64.0609181909090.4388@g5.osdl.org>
Date:	Mon, 18 Sep 2006 19:18:19 -0700 (PDT)
From:	Linus Torvalds <torvalds@...l.org>
To:	Jesper Juhl <jesper.juhl@...il.com>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	billm@...bpc.org.au
Subject: Re: Math-emu kills the kernel on Athlon64 X2

On Tue, 19 Sep 2006, Jesper Juhl wrote:
> 
> Booting with: vga=normal no387 nofxsr
> gets me no forther.   These are all the messages I get:
> 
> boot: 2.6.18rc7git2 vga=normal no387 nofxsr
> Loading 2.6.18rc7git2...................................
> BIOS data check successful
> Uncompressing Linux... Ok, booting the kernel.
> 
> And then the system hangs and requires a power cycle.
> 
> So unfortunately that does't help much :-(

Ok. The next phase is to try to figure out where it hangs, and since it 
happens very early, that's most often most easily done the hard way: add 
some code that reboots the machine, and if the machine hangs, you didn't 
reach it.

These days there's a slightly easier approach: if you enable PM_TRACE 
support (you need to enable PM and PM_DEBUG and EXPERIMENTAL to get it), 
you can do

	#include <resume-trace.h>

at the top of a file, and add a sprinkling of "TRACE_RESUME(x)" calls 
(where "x" is some integer in the range 0-15 that you can use to save off 
the iteration count in a loop, for example - leave at 0 if you're not 
interested).

And then, when it hangs, once you reboot into the same kernel (without the 
"no387", so that it works ;), it should tell you where the last 
trace-point was fairly early in the bootup dmesg's.

(It _will_ screw up your time-of-day clock in the process, though, which 
is why tracing is so hard to enable on purpose ;)

		Linus
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