sunrpc uses sleep_on to wait until the rpciod thread has died. This
could race if rpciod_down is called without lock_kernel. Right now all
calls in the main tree are under lock_kernel, but rpciod is an exported
function and sleep_on should die.
Additionally, I've replaced spin_lock_irqsave() with spin_lock_irq():
rpciod_down sleeps, interrupts are guaranteed to be enabled.

--
        Manfred