Description of problem:

*pde = 00000000                      
Oops: 0000                      

CPU:    1                      
EIP:    0060:[<c011d601>]    Not tainted                      
EFLAGS: 00000046                      

EIP is at try_to_wake_up [kernel] 0x21 (2.4.20-8smp)                      
eax: 00000000   ebx: c183dfa8   ecx: c183df9c   edx: c183df98                   
esi: 00000000   edi: 00000001   ebp: c183df7c   esp: c183df60                   
ds: 0068   es: 0068   ss: 0068                                             
Process swapper (pid: 5, stackpage=c183d000)                      
Stack: c183df8c 00000000 00000000 00000246 c183dfa8 c03ba280 00000001 c183df90  
c011d81e 00000000 00000007 00000000 c183dfc8 c011f870 00000282 c03bac1c   
c03bac1c c183c000 00000000 00000001 c183dfb0 c183dfb0 00000246 c183c000   
Call Trace:   [<c011d81e>] wake_up_process [kernel] 0x1e (0xc183df80))          
[<c011f870>] set_cpus_allowed [kernel] 0xd0 (0xc183df94))                      
[<c0129181>] ksoftirqd [kernel] 0x51 (0xc183dfcc))                           
[<c0129130>] ksoftirqd [kernel] 0x0 (0xc183dfe0))                      
[<c010759d>] kernel_thread_helper [kernel] 0x5 (0xc183dff0))

Looking at kernel code, migration_init does:

migration_call(smp_processor_id());  <<<<< 1
for (cpu = 0; cpu < smp_num_cpus; cpu++)
   if (cpu != smp_processor_id())    <<<<< 2
      migration_call(cpu);

Is there any code which ensures that we run on same CPUs in steps 1 and 2? I 
did not found anything ensuring that, and it could explain why migration_thread 
of some runqueue was NULL when we were starting ksoftirqd threads - 
migration_init started two migration threads on one of CPUs, while no thread on 
another...

Unfortunately problem is not easily reproducible, but as I see nothing changed 
in this area in 2.4.20-20.1.2007, I'm reporting it anyway although there are 
newer kernels available. I believe that 2.5.x is safe due to its use of cpu 
notifiers.


Version-Release number of selected component (if applicable):
kernel-smp-2.4.20-8, but I believe that 2.4.20-20.1.2007.nptl is affected too.

How reproducible:
Occassionaly.

Steps to Reproduce:
1.Get SMP machine
2.Install kernel-smp-2.4.20-8
3.Reboot it again and again
    
Actual results:
Sometime it crashes during bootup with oopses above.

Expected results:
No crash.