On Thu, Jun 17, 2010 at 01:56:35PM -0700, Greg KH wrote:
> On Thu, Jun 17, 2010 at 04:43:13PM -0400, Don Zickus wrote:
> > I have been trying to track down sources of unknown NMIs and spurious
> > interrupts recently using old fashion detective work of inspecting all
> > devices on the PCI bus to see what ERR/INT bits are set.
> >
> > Using a for-loop like this inside an NMI or interrupt context:
> >
> > err_bits = <some interesting value>
> > while ((dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev)) != NULL) {
> > pci_read_config_word(dev,0x6,&data);
> > if (data & err_bits)
> > printk(...<found what i was looking for>...);
> > }
> >
> > Of course every time this code gets executed the I get bit by the
> > WARN_ON(in_interrupt) inside of pci_get_dev_by_id().
>
> Yup, because that call can sleep.
>
> > I was trying to figure out why it was there. I don't see any locks inside
> > the call path or anything else that might be a no-no inside an interrupt
> > context. Perhaps I missed something? Or is there a better way to do what
> > I want to do calling lower level functions?
>
> The bus_find_device() call can sleep with the klist iterations that will
> happen.
Oh right. Somehow missed it. Thanks.
>
> This very issue came up a few months ago, check the archives :)
Ah. I see it.
>
> > I understand my code is hack'ish and there could be other sources of NMIs
> > or interrupts but for debugging purposes it sure is helping debug a bunch
> > of problems (related to firmware).
>
> Can't you get a better idea of which pci device caused the NMI without
> having to walk over every device in the system? Remember, PCI devices
Don't know. Do bridge devices store the device id of the generated
error/irq?
> can be removed at any point in time :)
that was why I walking the tree in the NMI/interrupt context instead of
using a boot-time generated list. But yes, I understand. This is just
for debugging because we seem to be spending weeks guessing which devices
are causing the problems.
Firmware is the new BIOS. :-/
Cheers,
Don
>
> thanks,
>
> greg k-h
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