sched/fair: Replace rcu_assign_pointer() with RCU_INIT_POINTER()

Author: Andreea-Cristina Bernat <bernat.ada@gmail.com>

The use of "rcu_assign_pointer()" is NULLing out the pointer.
According to RCU_INIT_POINTER()'s block comment:

  "1.   This use of RCU_INIT_POINTER() is NULLing out the pointer"

it is better to use it instead of rcu_assign_pointer() because it has a
smaller overhead.

The following Coccinelle semantic patch was used:
 @@
 @@

 - rcu_assign_pointer
 + RCU_INIT_POINTER
   (..., NULL)

Signed-off-by: Andreea-Cristina Bernat 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: paulmck@linux.vnet.ibm.com
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/20140822145043.GA580@ada
Signed-off-by: Ingo Molnar 

---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d3427a8..02fc949 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1780,7 +1780,7 @@ void task_numa_free(struct task_struct *p)
 		list_del(&p->numa_entry);
 		grp->nr_tasks--;
 		spin_unlock_irqrestore(&grp->lock, flags);
-		rcu_assign_pointer(p->numa_group, NULL);
+		RCU_INIT_POINTER(p->numa_group, NULL);
 		put_numa_group(grp);
 	}