[cpia] USB/SMP lockups

[George Talusan]

I've been getting major lockups (sysrq doesn't work) when
using my EZonics EZcam with an SMP-enabled kernel.  Switching
down to UP seems to not cause any lockups.

I have used the stock usb-uhci and JE's uhci modules and the
lock ups still happen.  The problem manifests itself when
open/close the camera repeated times.

The programs I've been using are gqcam and libbgrab.

My system is a dual Abit Bp6, 224mb, linux-2.4.0-test5.

Also, I've been looking at cpia.c and in cpia_register_camera
there is a comment nothing that the big kernel lock is acquired.
But lock_kernel() appears nowhere, yet unlock_kernel() appears
in the error paths (but not success!).  Adding in or removing
the appropriate lock/unlock pairs didn't seem to help any.

-- - gst
George Talusan, gstalusan@uwaterloo.ca