cond_synchronize_sched — Conditionally wait for an RCU-sched grace period
| void cond_synchronize_sched ( | unsigned long oldstate ); | 
   If a full RCU-sched grace period has elapsed since the earlier call to
   get_state_synchronize_sched, just return.  Otherwise, invoke
   synchronize_sched to wait for a full grace period.
   
Yes, this function does not take counter wrap into account. But counter wrap is harmless. If the counter wraps, we have waited for more than 2 billion grace periods (and way more on a 64-bit system!), so waiting for one additional grace period should be just fine.