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/exit.c b/kernel/exit.c
index 6f50ef5..5962d7c 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -933,7 +933,7 @@
 	 * an exiting task cleaning up the robust pi futexes.
 	 */
 	smp_mb();
-	spin_unlock_wait(&tsk->pi_lock);
+	raw_spin_unlock_wait(&tsk->pi_lock);
 
 	if (unlikely(in_atomic()))
 		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",