Re: PROBLEM: APIC on a Pentium Classic SMP, 2.4.21-pre2 and 2.4.21-pre3 ksymoops

[Maciej W. Rozycki]

On Wed, 10 Sep 2003, Mikael Pettersson wrote:

> First I found one very strange thing in Mathieu's boot log:
> 
> --- mpbug-2.4.20	Wed Sep 10 17:19:05 2003
> +++ mpbug-2.4.23-pre3	Wed Sep 10 17:18:44 2003
> ...
> +DMI not present.
>  Intel MultiProcessor Specification v1.1
>  Virtual Wire compatibility mode.
>  Default MP configuration #6
> 
> This means construct_default_ISA_mptable() still gets called.
> Ok so far.

 Yep -- I've been aware of this.

> At this point I was thinking "memory corruption",
> and the following struck me:
> 
> What used to be arrays (mp_irqs[] etc) are now pointers to
> memory which is sized and allocated by smp_read_mpc().
> In the case when construct_default_ISA_mptable() is called,
> smp_read_mpc() is _not_ called, the pointers never get initialised,
> and reads and writes of these arrays end up in la-la land.

 Exactly.

> The fix would be to add allocation and initialisation of
> these pointers at the start of construct_default_ISA_mptable().

 Possibly -- I haven't thought on how to fix it yet.

> I'll prepare a patch doing this sometime tomorrow.

 Thanks a lot for taking care.

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@xxxxxxxxxxxxx, PGP key available        +

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