SMP_LNGSPINWAIT

   SMP_LNGSPINWAIT establishes, in 10-microsecond intervals, the
   amount of time a CPU in an SMP system normally waits for access
   to a shared resource. This process is called spinwaiting.

   Generally spinlocks at IPL <= 8 have long holding times,
   therefore have their timeout intervals set to SMP_LNGSPINWAIT
   to prevent SPINWAIT timeouts in cases of nested acquisition.

   A timeout causes a CPUSPINWAIT bugcheck.

   The default value is 3000000 (30,00, 000 10-microsecond intervals
   or 30 second).