sched: Convert pi_lock to raw_spinlock

Convert locks which cannot be sleeping locks in preempt-rt to
raw_spinlocks.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/fork.c b/kernel/fork.c
index 1415dc4..9bd9144 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -939,9 +939,9 @@
 
 static void rt_mutex_init_task(struct task_struct *p)
 {
-	spin_lock_init(&p->pi_lock);
+	raw_spin_lock_init(&p->pi_lock);
 #ifdef CONFIG_RT_MUTEXES
-	plist_head_init(&p->pi_waiters, &p->pi_lock);
+	plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
 	p->pi_blocked_on = NULL;
 #endif
 }