Fwd: Fwd: How to determine which device crashes udev in boot?

Fwd: Fwd: How to determine which device crashes udev in boot?

[iwillallways forget1]

Greg K-H replied to me:
>> Some device has a working driver for Porteus's 64-bit kernel but a
>> crashing driver for Porteus's 32-bit kernel, and the crash is so hard
>> that it doesn't even start flashing two keyboard lights.  Also this
>> being text mode (when I type udevadm not startx), the crash is so hard
>> that it doesn't print an oops.
>
> Use a serial console, that way you can see the oops happen there.

Perhaps I should mention that I had
tail -f /var/log/messages >/mnt/sdb1/what 2>&1 &
running in the background before running udevd and udevadm trigger.
The log included udev stuff until the crash, but did not include the oops.

I think I own two USB-to-serial adapters and a serial reverse cable.
I'll have to hunt for them and bring them to my employer.
Do you think the oops will get out over a USB-to-serial adapter
before the kernel crashes hard?

(Several years ago I saved virtual serial output to a real file under
VMware and diagnosed an oops, but the NEC VF-6 is a real notebook with
some device that a VMware virtual PC doesn't have.)

Re: Fwd: Fwd: How to determine which device crashes udev in boot?

[Greg KH]

On Thu, Mar 17, 2016 at 05:54:10PM +0900, iwillallways forget1 wrote:
> Greg K-H replied to me:
> >> Some device has a working driver for Porteus's 64-bit kernel but a
> >> crashing driver for Porteus's 32-bit kernel, and the crash is so hard
> >> that it doesn't even start flashing two keyboard lights.  Also this
> >> being text mode (when I type udevadm not startx), the crash is so hard
> >> that it doesn't print an oops.
> >
> > Use a serial console, that way you can see the oops happen there.
> 
> Perhaps I should mention that I had
> tail -f /var/log/messages >/mnt/sdb1/what 2>&1 &
> running in the background before running udevd and udevadm trigger.
> The log included udev stuff until the crash, but did not include the oops.

Yes, that will not be saved as the kernel crashed.

> I think I own two USB-to-serial adapters and a serial reverse cable.
> I'll have to hunt for them and bring them to my employer.
> Do you think the oops will get out over a USB-to-serial adapter
> before the kernel crashes hard?

No, usb serial usually does not work for capturing oops messages because
the kernel crashes and USB needs interrupts to be running properly to
deliver data.

Try a "real" serial connection if the device has one.

As you know what kernel drivers are needed for this hardware (it works
in 64bit mode), just load them by hand, one by one, in 32bit mode and
see what one dies.

good luck,

greg k-h