The SMP case seems to have something wrong with it. My MARCH=p4 and -O optimized kernel often crashes when shutting down on beastieng.frontfree.net. Apparantly this is lock related (we can see the panic strings there not to be outputing atomically, and they just mixed with each other).

I’m still looking for the cause of the problem. Fortunatelly the core dumps correctly and it will be helpful. If I have no luck, then I will post the backtrace on -CURRENT.