Re: 2.6.7-rc1-bk: SMT scheduler bug / crashes on kernel boot

[Nick Piggin <nickpiggin@yahoo.com.au>]

Anton Altaparmakov wrote:
> On Wed, 2004-05-26 at 12:13, Nick Piggin wrote:
> 
>>Anton Altaparmakov wrote:
>>
>>>Hi,
>>>
>>>Kernel 2.6.7-rc1-bk crashes on boot with a NULL pointer dereference. 
>>>The kernel is running under VMware if that matters but I don't think it
>>>should.  It was working fine with 2.6.6-rc3-bk kernels.
>>>
>>>I am afraid the only way I could capture the crash was to capture the
>>>vmware screen into a PNG image which is attached.  Maybe I need to setup
>>>some OCR software for in the future...  (-;
>>>
>>>The system running VMware is a P4 2.6Hz with Hyper threading enabled and
>>>/proc/cpuinfo shows two cpus:
>>
>>OK, thanks for that. It would be quite helpful if you edit
>>kernel/sched.c and turn the line #undef SCHED_DOMAIN_DEBUG into
>>#define SCHED_DOMAIN_DEBUG, then compile a kernel with debugging
>>info enabled.
> 
> 
> Looking at kernel/sched.c it already says #define, not #undef!
> 

Oops, yes.

[snip]

> So the dereferencing of one of the two fails.  Considering the offset is
> 0x18 in the NULL dereference it must be the (p)->prio that causes the
> oops and hence p must be NULL.  I will leave you to figure out what that
> means...
> 

Nice detective work.

It tried to dereference a NULL idle thread I'd say.
ie. the CPU hasn't been set up. Please try Ingo's patch.