sched/core: Annotate curr pointer in rq with __rcu

This patch fixes the following sparse warnings in sched/core.c
and sched/membarrier.c:

  kernel/sched/core.c:2372:27: error: incompatible types in comparison expression
  kernel/sched/core.c:4061:17: error: incompatible types in comparison expression
  kernel/sched/core.c:6067:9: error: incompatible types in comparison expression
  kernel/sched/membarrier.c:108:21: error: incompatible types in comparison expression
  kernel/sched/membarrier.c:177:21: error: incompatible types in comparison expression
  kernel/sched/membarrier.c:243:21: error: incompatible types in comparison expression

Signed-off-by: Madhuparna Bhowmik <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: Madhuparna Bhowmik

kernel/sched/sched.h

@@ -896,7 +896,7 @@ struct rq {
 	 */
 	unsigned long		nr_uninterruptible;
 
-	struct task_struct	*curr;
+	struct task_struct __rcu	*curr;
 	struct task_struct	*idle;
 	struct task_struct	*stop;
 	unsigned long		next_balance;