dev_close() must be called holding the RTNL.  Compile-tested only.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
 #include <linux/x25.h>
 #include <linux/lapb.h>
 #include <linux/init.h>
+#include <linux/rtnetlink.h>
 #include "x25_asy.h"
 
 #include <net/x25device.h>
        if (!sl || sl->magic != X25_ASY_MAGIC)
                return;
 
+       rtnl_lock();
        if (sl->dev->flags & IFF_UP)
                dev_close(sl->dev);
+       rtnl_unlock();
 
        tty->disc_data = NULL;
        sl->tty = NULL;