[AX25] ax25_ds_timer: use mod_timer instead of add_timer

This patch changes current use of: init_timer(), add_timer()
and del_timer() to setup_timer() with mod_timer(), which
should be safer anyway.
Reported-by: Jann Traschewski <jann@gmx.de>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ax25.h

@@ -324,6 +324,7 @@ extern void ax25_dama_on(ax25_cb *);
 extern void ax25_dama_off(ax25_cb *);
 
 /* ax25_ds_timer.c */
+extern void ax25_ds_setup_timer(ax25_dev *);
 extern void ax25_ds_set_timer(ax25_dev *);
 extern void ax25_ds_del_timer(ax25_dev *);
 extern void ax25_ds_timer(ax25_cb *);

net/ax25/ax25_dev.c

@@ -82,7 +82,7 @@ void ax25_dev_device_up(struct net_device *dev)
 	ax25_dev->values[AX25_VALUES_DS_TIMEOUT]= AX25_DEF_DS_TIMEOUT;
 
 #if defined(CONFIG_AX25_DAMA_SLAVE) || defined(CONFIG_AX25_DAMA_MASTER)
-	init_timer(&ax25_dev->dama.slave_timer);
+	ax25_ds_setup_timer(ax25_dev);
 #endif
 
 	spin_lock_bh(&ax25_dev_lock);

net/ax25/ax25_ds_timer.c

@@ -40,13 +40,10 @@ static void ax25_ds_timeout(unsigned long);
  *	1/10th of a second.
  */
 
-static void ax25_ds_add_timer(ax25_dev *ax25_dev)
+void ax25_ds_setup_timer(ax25_dev *ax25_dev)
 {
-	struct timer_list *t = &ax25_dev->dama.slave_timer;
-	t->data		= (unsigned long) ax25_dev;
-	t->function	= &ax25_ds_timeout;
-	t->expires	= jiffies + HZ;
-	add_timer(t);
+	setup_timer(&ax25_dev->dama.slave_timer, ax25_ds_timeout,
+		    (unsigned long)ax25_dev);
 }
 
 void ax25_ds_del_timer(ax25_dev *ax25_dev)
@@ -60,10 +57,9 @@ void ax25_ds_set_timer(ax25_dev *ax25_dev)
 	if (ax25_dev == NULL)		/* paranoia */
 		return;
 
-	del_timer(&ax25_dev->dama.slave_timer);
 	ax25_dev->dama.slave_timeout =
 		msecs_to_jiffies(ax25_dev->values[AX25_VALUES_DS_TIMEOUT]) / 10;
-	ax25_ds_add_timer(ax25_dev);
+	mod_timer(&ax25_dev->dama.slave_timer, jiffies + HZ);
 }
 
 /*