Can you try a 'strace -fp PID' when it's in the state of spinning with system CPU time? I'm wondering whether it's stuck in a single syscall or just spinning around one or a set of syscalls.
I have very vague recollections of a discussion on the list a few months ago about triggering a kernel bug that involved being stuck in system cpu spin... but I may be mis-remembering. -- / Peter Schuller
