Re: Dom0 crashing when built with c/s 881 (Was: [Xen-devel] blktap2: need more than 3 values to unpack)

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

If memory corruption is the issue, c/s 881 could be innocently triggering a
latent bug.

 -- Keir

On 04/06/2009 05:49, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> I'm quitting for the night now, but I see that
> the string "nous" is followed by a "b" in the
> immediately following word.  Put this together
> and you have "nousb"  (read as turn off USB).
> 
> Given that the "Driver 'xxx' needs updating"
> are for 'usbfs', 'hub', and 'usb', and given
> that usb is very related to hotplug, the string
> "nousb" where a pair of function pointers should
> be is suspicious (though it may also be a complete
> coincidence).
> 
> I'll try turning off CONFIG_HOTPLUG_PCI tomorrow.
> 
> Dan
> 
>> -----Original Message-----
>> From: Dan Magenheimer
>> Sent: Wednesday, June 03, 2009 7:09 PM
>> To: Keir Fraser; Isaku Yamahata
>> Cc: Xen-Devel (E-mail)
>> Subject: RE: Dom0 crashing when built with c/s 881 (Was: [Xen-devel]
>> blktap2: need more than 3 values to unpack)
>> 
>> 
>>> If that doesn't help, I can go add some printk's where that
>>> output is happening and see exactly what forces the failure.
>> 
>> Here's what I am seeing.  Looks like the drv->bus structure
>> is getting overwritten with ASCII.
>> 
>> Driver 'usbfs' needs updating - please use bus_type methods
>> drv->bus->probe = 73756f6e  (THAT's "nous" I think)
>> drv->probe = d1069ab0
>> drv->bus->remove = 00000062
>> drv->remove = d1069960
>> drv->bus->shutdown = 00000000
>> drv->shutdown = 00000000
>> usbcore: registered new driver usbfs
>> Driver 'hub' needs updating - please use bus_type methods
>> drv->bus->probe = 73756f6e
>> drv->probe = d1069ab0
>> drv->bus->remove = 00000062
>> drv->remove = d1069960
>> drv->bus->shutdown = 00000000
>> drv->shutdown = 00000000
>> usbcore: registered new driver hub
>> Driver 'usb' needs updating - please use bus_type methods
>> drv->bus->probe = 73756f6e
>> drv->probe = d1069570
>> 
>>> -----Original Message-----
>>> From: Dan Magenheimer
>>> Sent: Wednesday, June 03, 2009 4:12 PM
>>> To: Keir Fraser; Isaku Yamahata
>>> Cc: Xen-Devel (E-mail)
>>> Subject: RE: Dom0 crashing when built with c/s 881 (Was: [Xen-devel]
>>> blktap2: need more than 3 values to unpack)
>>> 
>>> 
>>>> Actually I missed that the dependent code is only built if
>>>> CONFIG_PCI_IOMULTI && CONFIG_HOTPLUG_PCI. You've probably got
>>>> one or both
>>>> disabled and hence 882 doesn't break without 881 in your case.
>>> 
>>> In case it helps, with 889 and 881 reverted, I am using the
>>> default config which results in CONFIG_PCI_IOMULTI=y and
>>> CONFIG_HOTPLUG_PCI=m.
>>> 
>>>> I can't explain that from reading the code. It looks like a
>>>> no-op to me
>>>> unless the new function bus_register_notifier() is called.
>>> 
>>> Looking at my boot output on failure, there are those lines:
>>> 
>>> "Driver 'xxx' needs updating - please use bus_type methods"
>>> 
>>> which is printed in linux/drivers/base/driver.c:driver_register()
>>> if a complex set of circumstances are true.  So clearly
>>> something is different.
>>> 
>>> If that doesn't help, I can go add some printk's where that
>>> output is happening and see exactly what forces the failure.
>>> 
>>> Dan
>>> 
>>> 
>>>> -----Original Message-----
>>>> From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
>>>> Sent: Wednesday, June 03, 2009 3:28 PM
>>>> To: Dan Magenheimer; Isaku Yamahata
>>>> Cc: Xen-Devel (E-mail)
>>>> Subject: Re: Dom0 crashing when built with c/s 881 (Was:
>> [Xen-devel]
>>>> blktap2: need more than 3 values to unpack)
>>>> 
>>>> 
>>>> On 03/06/2009 22:17, "Dan Magenheimer"
>>>> <dan.magenheimer@xxxxxxxxxx> wrote:
>>>> 
>>>>>>  1. It only adds extra functionality which by default would
>>>>>> not do anything.
>>>>>> Just reading the patch I can see it's harmless by itself
>>>> as it merely
>>>>>> introduces a new notifier chain which noone registers on.
>>>>> 
>>>>> I won't pretend to understand the code, but I did
>>>>> reproduce the problem with 881 by itself and with
>>>>> 889 with 881 reverted.
>>>> 
>>>> I can't explain that from reading the code. It looks like a
>>>> no-op to me
>>>> unless the new function bus_register_notifier() is called.
>>>> 
>>>>>>  2. Changeset 882 depends on 881. If you revert just 881 then
>>>>>> the tree will not build.
>>>>> 
>>>>> This doesn't appear to be the case for me, though
>>>>> I'm certainly willing to believe there's something
>>>>> wrong with my process:
>>>> 
>>>> Actually I missed that the dependent code is only built if
>>>> CONFIG_PCI_IOMULTI && CONFIG_HOTPLUG_PCI. You've probably got
>>>> one or both
>>>> disabled and hence 882 doesn't break without 881 in your case.
>>>> 
>>>>  -- Keir
>>>> 
>>>> 
>>>> 



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