The new lost-tick detection code is pretty cool, but it can be
relatively uninformative when something using the
common_interrupt->do_IRQ path keeps interrupts disabled for a long time.
This patch will record the last interrupt on the current CPU, and spit
it out along with the stack trace.

There are no guarantees here.  If preemption is enabled, all bets are
off, and this data could be incorrect.  It would be relatively silly to
disable preemption, just to get some debugging data to be more accurate.

Warning! Detected 4094446 micro-second gap between interrupts.
  Compensating for 4093 lost ticks.
Call Trace:
 [<c010ab60>] handle_IRQ_event+0x28/0x50
 [<c010ad44>] do_IRQ+0xa0/0x10c
 [<c01097b3>] common_interrupt+0x43/0x58
  Last run common irq: 24: eth2


-- 
Dave Hansen
haveblue@us.ibm.com