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Date:	Mon, 26 Oct 2009 14:16:34 -0700
From:	"Justin P. Mattock" <justinmattock@...il.com>
To:	Valdis.Kletnieks@...edu
CC:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Bernhard Kaindl <bk@...e.de>
Subject: Re: PANIC: early exception 08 rip 246:10 error ffffffff810251b5 cr2
 0

Valdis.Kletnieks@...edu 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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