futex,plist: Remove debug lock assignment from plist_node

The original code uses &plist_node->plist as the fake head of
the priority list for plist_del(), these debug locks in
the fake head are needed for CONFIG_DEBUG_PI_LIST.

But now we always pass the real head to plist_del(), the debug locks
in plist_node will not be used, so we remove these assignments.

Acked-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by:  Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4D10797E.7040803@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/futex.c

@@ -1089,9 +1089,6 @@ void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1,
 		plist_del(&q->list, &hb1->chain);
 		plist_add(&q->list, &hb2->chain);
 		q->lock_ptr = &hb2->lock;
-#ifdef CONFIG_DEBUG_PI_LIST
-		q->list.plist.spinlock = &hb2->lock;
-#endif
 	}
 	get_futex_key_refs(key2);
 	q->key = *key2;
@@ -1124,9 +1121,6 @@ void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key,
 	q->rt_waiter = NULL;
 
 	q->lock_ptr = &hb->lock;
-#ifdef CONFIG_DEBUG_PI_LIST
-	q->list.plist.spinlock = &hb->lock;
-#endif
 
 	wake_up_state(q->task, TASK_NORMAL);
 }
@@ -1474,9 +1468,6 @@ static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
 	prio = min(current->normal_prio, MAX_RT_PRIO);
 
 	plist_node_init(&q->list, prio);
-#ifdef CONFIG_DEBUG_PI_LIST
-	q->list.plist.spinlock = &hb->lock;
-#endif
 	plist_add(&q->list, &hb->chain);
 	q->task = current;
 	spin_unlock(&hb->lock);