s390/3215: fix hanging console issue

commit 26d766c6 upstream.

The ccw_device_start in raw3215_start_io can fail. raw3215_try_io
does not check if the request could be started and removes any
pending timer. This can leave the system in a hanging state.
Check for pending request after raw3215_start_io and start a
timer if necessary.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/s390/char/con3215.c

@@ -288,12 +288,16 @@ static void raw3215_timeout(unsigned long __data)
 	unsigned long flags;
 
 	spin_lock_irqsave(get_ccwdev_lock(raw->cdev), flags);
-	if (raw->flags & RAW3215_TIMER_RUNS) {
-		del_timer(&raw->timer);
 	raw->flags &= ~RAW3215_TIMER_RUNS;
 	if (!(raw->port.flags & ASYNC_SUSPENDED)) {
 		raw3215_mk_write_req(raw);
 		raw3215_start_io(raw);
+		if ((raw->queued_read || raw->queued_write) &&
+		    !(raw->flags & RAW3215_WORKING) &&
+		    !(raw->flags & RAW3215_TIMER_RUNS)) {
+			raw->timer.expires = RAW3215_TIMEOUT + jiffies;
+			add_timer(&raw->timer);
+			raw->flags |= RAW3215_TIMER_RUNS;
 		}
 	}
 	spin_unlock_irqrestore(get_ccwdev_lock(raw->cdev), flags);
@@ -317,17 +321,15 @@ static inline void raw3215_try_io(struct raw3215_info *raw)
 		    (raw->flags & RAW3215_FLUSHING)) {
 			/* execute write requests bigger than minimum size */
 			raw3215_start_io(raw);
-			if (raw->flags & RAW3215_TIMER_RUNS) {
-				del_timer(&raw->timer);
-				raw->flags &= ~RAW3215_TIMER_RUNS;
 		}
-		} else if (!(raw->flags & RAW3215_TIMER_RUNS)) {
-			/* delay small writes */
+	}
+	if ((raw->queued_read || raw->queued_write) &&
+	    !(raw->flags & RAW3215_WORKING) &&
+	    !(raw->flags & RAW3215_TIMER_RUNS)) {
 		raw->timer.expires = RAW3215_TIMEOUT + jiffies;
 		add_timer(&raw->timer);
 		raw->flags |= RAW3215_TIMER_RUNS;
 	}
-	}
 }
 
 /*