SMP, "classic" biglock


as soon as one CPU enters kernel, no other can
syscalls, interrupts

other CPUs will block until first is done and releases biglock

need finer grained locking
or lock-free data structures where possible
without trainwreck release(s) as seen elsewhere

ongoing work for ages, but dependencies...
always some dependency in the way of unlocking subsystems/syscalls
improvements coming fast right now