Hello everyone,

Summary:
Kernel Oops caused by multiple access requests to a single scanner
through libusb.

Detailed description:
The following script leads to an kernel oops on my System:
#!/bin/bash
scanimage > test &
scanimage -h

This is because scanimage -h tries to append a list of availlable
scanners to the help output and thus interferes with the first
scanimage process which is initializing the scanner at the same
moment. I am using the kernel 2.6.5 and the usb host controller
ohci-hcd. The kernel is tainted because I am using the loop-aes module
and the mppe patch from pptpclient.sf.net/mppe/ which should not
interfere with the scanning process.

Relevant kernel logs and the output of ksymoops applied to those logs
are attached seperately. Please let me know if you need any further
information.
Btw: After the occurrence of the kernel oops I tried a
# modprobe -r ohci-hcd

After showing some messages which indicated modprobe's effort to
process the command, modprobe hang it even
kill -9 pid
or
killall -9 modprobe
could not stop the process. When rebooting the system stopped during
shut down when it tried to stop alsa (most likely, because it uses
modprobe to unload the alsa related modules at this point).

Best regards,

Elias