One also wonders about whether all the RCU stuff is needed on UP. I'mPreempt can happen anytime, I believe.
not sure if I grok all the finepoints here, but it looks like the
answer is no and that we can make struct_rcu head empty and have
call_rcu fall directly through to the callback. This would save
something like 16-32 bytes (32/64bit), not to mention a bunch of
dinking around with lists and whatnot.
So what am I missing?