The RCU callback free_head just calls kfree(), so we can use kfree_rcu()
instead of call_rcu().
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>