2.4 kernel hangs on 486 machine at boot

2.4 kernel hangs on 486 machine at boot

[Vik Heyndrickx]

Hello,

Problem: Linux kernel 2.4 consistently hangs at boot on 486 machine

Shortly after lilo starts the kernel it hangs at the following message:
Checking if this processor honours the WP bit even in supervisor mode...
<blinking cursor>

I experience this problem on a VLB AMD 486 DX/2-66 system. This machine ran
all kernels up to 2.2.18 without any problem (it still does).

This 2.4 kernel runs fine on a Pentium, Pentium II and even on a _386DX_
(!!!), but not on my 486 machine (which I am using as a router, and I
thought: let's try the netfilter/iptables feature :) on it).

I tried both the precompiled 2.4 kernels from the Redhat linux releases and
betas, and a couple of self-compiled stock kernels (2.4.0 and 2.4.2) from
ftp://ftp.kernel.org/

Anyway I find it obvious that the kernel hangs only on 486's (and probably
not all of them), so it must be a bug (can I call this an oops? ;-))
I'm not familiar enough with the kernel and protected mode x86 asm to
correct this problem myself, but if anyone would know what may be causing
this (probably in arch/i386/mm/init.c) I can rebuild, install and test any
supplied patches (don't send entire precompiled kernels to me, please).

BTW Keep in mind that I'm not on any kernel related mailing list, but I like
to be informed.

Thanks & kind regards,

--
Vik

Re: 2.4 kernel hangs on 486 machine at boot

[Alan Cox]

> Problem: Linux kernel 2.4 consistently hangs at boot on 486 machine
> 
> Shortly after lilo starts the kernel it hangs at the following message:
> Checking if this processor honours the WP bit even in supervisor mode...
> <blinking cursor>

Does this happen on 2.4.3-ac kernel trees ? I thought i had it zapped

> 

Re: 2.4 kernel hangs on 486 machine at boot

[Vik Heyndrickx]

----- Original Message -----
From: "Alan Cox" <alan@lxorguk.ukuu.org.uk>
To: "Vik Heyndrickx" <vik.heyndrickx@pandora.be>
Cc: <rhw@memalpha.cx>; <linux-kernel@vger.kernel.org>;
<rgooch@atnf.csiro.au>
Sent: Wednesday, April 04, 2001 7:54 PM
Subject: Re: 2.4 kernel hangs on 486 machine at boot


> > Problem: Linux kernel 2.4 consistently hangs at boot on 486 machine
> >
> > Shortly after lilo starts the kernel it hangs at the following message:
> > Checking if this processor honours the WP bit even in supervisor mode...
> > <blinking cursor>
>
> Does this happen on 2.4.3-ac kernel trees ? I thought i had it zapped

It doesn't even happen with with 2.4.3. Now I feel silly.

--
Vik

Re: 2.4 kernel hangs on 486 machine at boot

[Brian Gerst]

Alan Cox wrote:
> 
> > Problem: Linux kernel 2.4 consistently hangs at boot on 486 machine
> >
> > Shortly after lilo starts the kernel it hangs at the following message:
> > Checking if this processor honours the WP bit even in supervisor mode...
> > <blinking cursor>
> 
> Does this happen on 2.4.3-ac kernel trees ? I thought i had it zapped
> 

Yes, that fix in -ac should take care of it.  As to why only the 486
showed the problem, most 386's will not fault on the write protected
page (the whole reason for this test) and pentiums and later don't run
the test at all (assumed good).

--

				Brian Gerst

Re: 2.4 kernel hangs on 486 machine at boot

[Pavel Machek]

Hi!

> > > Problem: Linux kernel 2.4 consistently hangs at boot on 486 machine
> > >
> > > Shortly after lilo starts the kernel it hangs at the following message:
> > > Checking if this processor honours the WP bit even in supervisor mode...
> > > <blinking cursor>
> > 
> > Does this happen on 2.4.3-ac kernel trees ? I thought i had it zapped
> 
> Yes, that fix in -ac should take care of it.  As to why only the 486
> showed the problem, most 386's will not fault on the write protected
> page (the whole reason for this test) and pentiums and later don't run
> the test at all (assumed good).

We should not "assume good" -- to catch bugs like this one.
-- 
Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt,
details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.

Re: 2.4 kernel hangs on 486 machine at boot

[Brian Gerst]

Pavel Machek wrote:
> 
> Hi!
> 
> > > > Problem: Linux kernel 2.4 consistently hangs at boot on 486 machine
> > > >
> > > > Shortly after lilo starts the kernel it hangs at the following message:
> > > > Checking if this processor honours the WP bit even in supervisor mode...
> > > > <blinking cursor>
> > >
> > > Does this happen on 2.4.3-ac kernel trees ? I thought i had it zapped
> >
> > Yes, that fix in -ac should take care of it.  As to why only the 486
> > showed the problem, most 386's will not fault on the write protected
> > page (the whole reason for this test) and pentiums and later don't run
> > the test at all (assumed good).
> 
> We should not "assume good" -- to catch bugs like this one.

Well, in this case we cannot do the test if we enabled PSE (we would
mark the whole 4MB page read-only).  The test would have to use a
different page.

--
						Brian Gerst