Re: PANIC: early exception 08 rip 246:10 error ffffffff810251b5 cr20

[Justin P. Mattock]

Valdis.Kletnieks@xxxxxx wrote:
> On Mon, 26 Oct 2009 11:34:20 PDT, Justin Mattock said:
>
>    
> > I can't seem to locate a right mailing list
> > for ieee1394 for Linux. Anyways here is a
> > url to flickr which has the image of the PANIC:
> > http://www.flickr.com/photos/44066293@N08/4046711653/
> > (hopefully you don't need to sign up to view)
> >
> > As for the problem, interesting thing here is if I add
> > a printk to:
> >
> > if ((class == 0xffffffff))
> > printk(KERN_BUG "init_ohci1394_dma: finished initializing OHCI DMA\n");
> > continue; /* No device at this func */
> >
> > the system will boot-up, and the PANIC will not occur.
> >      
>
> Note that just sticking a printk in there without a { } pair enclosing
> the printk and continue will change the semantics drastically - if the
> conditional is true, it will do the printk instead of continuing. And
> possibly more important, the continue just became unconditional.
>
> What *exactly* does your code look like now?
>    
as of now in init_ohci1394_dma.c
I did:



void __init init_ohci1394_dma_on_all_controllers(void)
{
    int num, slot, func;

    if (!early_pci_allowed())
        return;

    /* Poor man's PCI discovery, the only thing we can do at early boot */
    for (num = 0; num < 32; num++) {
        for (slot = 0; slot < 32; slot++) {
            for (func = 0; func < 8; func++) {
                u32 class = read_pci_config(num,slot,func,
                            PCI_CLASS_REVISION);
                if ((class == 0xffffffff))
+                    printk(KERN_DEBUG "putting a printk here keeps the 
machine from a panic\n");
                    continue; /* No device at this func */

                if (class>>8 != PCI_CLASS_SERIAL_FIREWIRE_OHCI)
                    continue; /* Not an OHCI-1394 device */

                init_ohci1394_controller(num, slot, func);
                break; /* Assume one controller per device */
            }
        }
    }
    printk(KERN_INFO "init_ohci1394_dma: finished initializing OHCI 
DMA\n");
}


interesting thing here, is I just was wanting to see were this thing was
crashing. when adding this in(above) Ill see a long string during boot
for a few seconds and then the machine boots up.
 Now if I add a printk(example below) to here:



void __init init_ohci1394_dma_on_all_controllers(void)
{
    int num, slot, func;

    if (!early_pci_allowed())
        return;

    /* Poor man's PCI discovery, the only thing we can do at early boot */
    for (num = 0; num < 32; num++) {
        for (slot = 0; slot < 32; slot++) {
            for (func = 0; func < 8; func++) {
                u32 class = read_pci_config(num,slot,func,
                            PCI_CLASS_REVISION);
                if ((class == 0xffffffff))
                    continue; /* No device at this func */

                if (class>>8 != PCI_CLASS_SERIAL_FIREWIRE_OHCI)
+                    printk(KERN_DEBUG "putting a printk here keeps the 
machine from a panic\n");
                    continue; /* Not an OHCI-1394 device */

                init_ohci1394_controller(num, slot, func);
                break; /* Assume one controller per device */
            }
        }
    }
    printk(KERN_INFO "init_ohci1394_dma: finished initializing OHCI 
DMA\n");
}



In dmesg I will see maybe 5 to 10 debug messages and then
onto init_ohci1394_initialize.
keep in mind I'm not familiar with any of this, but just looking
at the code I see 0xffffffff and searching(google) tells me
that that's something with 32bit, should maybe there be something
with 0xffffffffffffffffff 64bit?

Justin P. Mattock


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