On Tue, 12 May 2009 11:28:00 +0200 Wolfgang Grandegger <wg@xxxxxxxxxxxxxx> wrote:
+int can_restart_now(struct net_device *dev)
+{
+ struct can_priv *priv = netdev_priv(dev);
+ struct net_device_stats *stats = &dev->stats;
+ struct sk_buff *skb;
+ struct can_frame *cf;
+ int err;
+
+ /* Synchronize with dev->hard_start_xmit() */
+ netif_tx_lock(dev);
+
+ /* Ensure that no more messages can go out */
+ if (netif_carrier_ok(dev))
+ netif_carrier_off(dev);
+
+ /* Ensure that no more messages can come in */
+ err = priv->do_set_mode(dev, CAN_MODE_STOP);
+ if (err)
+ return err;
+
+ /* Now it's save to clean up */
+ del_timer_sync(&priv->restart_timer);
This is deadlockable.
It calls del_timer_sync() while holding netif_tx_lock(). But the timer
handler (can_restart_now()) also takes netif_tx_lock(). So if the
timer handler is presently running, it's sitting there spinning in
netif_tx_lock(). And del_timer_sync() is sitting there waiting for the
timer handler to complete.