From: Rusty Russell <rusty@rustcorp.com.au>

The IA64 hotplug CPU merge seems to have included some core changes: in
particular the recalc_bh_state() needs to sum for all (including offline)
cpus, since we don't empty the counters on CPU down.  The totals printed by
/proc/stat (the first loop) should include offline cpus, too (apparently
printing out the per-cpu lines for offline cpus confuses top).