Commit 0db3dc73 authored Jun 27, 2007 by Stephen Hemminger Committed by David S. Miller Jun 27, 2007

[NETPOLL]: tx lock deadlock fix



If sky2 device poll routine is called from netpoll_send_skb, it would
deadlock. The netpoll_send_skb held the netif_tx_lock, and the poll
routine could acquire it to clean up skb's. Other drivers might use
same locking model.

The driver is correct, netpoll should not introduce more locking
problems than it causes already. So change the code to drop lock
before calling poll handler.

Signed-off-by: Stephen Hemminger <shemminger@linux.foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 48d8d7ee

net/core/netpoll.c

+10 −9

Original line number	Diff line number	Diff line
		@@ -250,23 +250,24 @@ static void netpoll_send_skb(struct netpoll np, struct sk_buff skb)
		unsigned long flags;

		local_irq_save(flags);
		if (netif_tx_trylock(dev)) {
		/* try until next clock tick */
		for (tries = jiffies_to_usecs(1)/USEC_PER_POLL;
		tries > 0; --tries) {
		if (netif_tx_trylock(dev)) {
		if (!netif_queue_stopped(dev))
		status = dev->hard_start_xmit(skb, dev);
		netif_tx_unlock(dev);

		if (status == NETDEV_TX_OK)
		break;

		}

		/* tickle device maybe there is some cleanup */
		netpoll_poll(np);

		udelay(USEC_PER_POLL);
		}
		netif_tx_unlock(dev);
		}
		local_irq_restore(flags);
		}

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