[S390] qdio: add missing tiq_list locking

Add a mutex to protect the tiq_list. Although reading the list is done
using RCU adding and removing elements from the list must still
happen locked since multiple qdio devices may change the list in parallel
otherwise.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/qdio_main.c

@@ -1112,6 +1112,7 @@ int qdio_shutdown(struct ccw_device *cdev, int how)
 	if (!irq_ptr)
 		return -ENODEV;
 
+	BUG_ON(irqs_disabled());
 	DBF_EVENT("qshutdown:%4x", cdev->private->schid.sch_no);
 
 	mutex_lock(&irq_ptr->setup_mutex);

drivers/s390/cio/qdio_thinint.c

@@ -31,6 +31,7 @@
 
 /* list of thin interrupt input queues */
 static LIST_HEAD(tiq_list);
+DEFINE_MUTEX(tiq_list_lock);
 
 /* adapter local summary indicator */
 static unsigned char *tiqdio_alsi;
@@ -95,10 +96,10 @@ void tiqdio_add_input_queues(struct qdio_irq *irq_ptr)
 	if (!css_qdio_omit_svs && irq_ptr->siga_flag.sync)
 		css_qdio_omit_svs = 1;
 
-	for_each_input_queue(irq_ptr, q, i) {
+	mutex_lock(&tiq_list_lock);
+	for_each_input_queue(irq_ptr, q, i)
 		list_add_rcu(&q->entry, &tiq_list);
-		synchronize_rcu();
-	}
+	mutex_unlock(&tiq_list_lock);
 	xchg(irq_ptr->dsci, 1);
 	tasklet_schedule(&tiqdio_tasklet);
 }
@@ -118,7 +119,10 @@ void tiqdio_remove_input_queues(struct qdio_irq *irq_ptr)
 		/* if establish triggered an error */
 		if (!q || !q->entry.prev || !q->entry.next)
 			continue;
+
+		mutex_lock(&tiq_list_lock);
 		list_del_rcu(&q->entry);
+		mutex_unlock(&tiq_list_lock);
 		synchronize_rcu();
 	}
 }