Re: [discuss] [OOPS] powernow on smp dual core amd64

Zachary Amsden
2005-06-13T23:20:41Z

Tom Duffy wrote:

>On Mon, 2005-06-13 at 16:47 -0500, Langsdorf, Mark wrote:
>
>
>>Okay, I think I have figured this out. During initialization,
>>the cpufreq infrastruture only initializes the first core of
>>each processor. When a request comes into the second core,
>>it's data structre is unitialized and we get the null point
>>dereference.
>>
>>The solution is to assign the pointer to the data structure for
>>the first core to all the other cores.
>>
>>Tom, could you try this patch and see if it helps?
>>
>>
>
>Yes! It fixed the panic. I get much further.
>
>Thanks!
>
>Unfortunately, after starting cpuspeed daemon, I get this:
>
>Starting cpuspeed: [ OK ]
>Starting pcmcia: Starting PCMCIA services:
>CPU 6: Machine Check Exception: 4 Bank 4: b200000000070f0f
>TSC 4129a3d70d
>Kernel panic - not syncing: Machine check
> <1>Unable to handle kernel NULL pointer dereference at 00000000000000ff RIP:
>[<00000000000000ff>]
>
>

asmlinkage void smp_call_function_interrupt(void)
{
void (*func) (void *info) = call_data->func;
void *info = call_data->info;
int wait = call_data->wait;

ack_APIC_irq();
/*
* Notify initiating CPU that I've grabbed the data and am
* about to execute the function
*/
mb();
atomic_inc(&call_data->started);
/*
* At this point the info structure may be out of scope unless
wait==1
*/
irq_enter();
(*func)(info); <--- passed bogus data

Looks like you jumped through a bogus function pointer. I'm guessing it
has something to do with an unitialized IRQ vector for the CPU speed on
one of the cores (simply because it seems somewhat plausible):

extern u8 irq_vector[NR_IRQ_VECTORS];
#define IO_APIC_VECTOR(irq) (irq_vector[irq])
#define AUTO_ASSIGN -1

So irq_vector[AUTO_ASSIGN] = 0xff which could have somehow made it into
your function pointer.

Just a theory.