Commit d667f785 authored Nov 07, 2016 by Benjamin Poirier Committed by David S. Miller Nov 09, 2016

bna: Add synchronization for tx ring.



We received two reports of BUG_ON in bnad_txcmpl_process() where
hw_consumer_index appeared to be ahead of producer_index. Out of order
write/read of these variables could explain these reports.

bnad_start_xmit(), as a producer of tx descriptors, has a few memory
barriers sprinkled around writes to producer_index and the device's
doorbell but they're not paired with anything in bnad_txcmpl_process(), a
consumer.

Since we are synchronizing with a device, we must use mandatory barriers,
not smp_*. Also, I didn't see the purpose of the last smp_mb() in
bnad_start_xmit().

Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f91d7181

drivers/net/ethernet/brocade/bna/bnad.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -177,6 +177,7 @@ bnad_txcmpl_process(struct bnad bnad, struct bna_tcb tcb)
		return 0;

		hw_cons = *(tcb->hw_consumer_index);
		rmb();
		cons = tcb->consumer_index;
		q_depth = tcb->q_depth;

		@@ -3094,7 +3095,7 @@ bnad_start_xmit(struct sk_buff skb, struct net_device netdev)
		BNA_QE_INDX_INC(prod, q_depth);
		tcb->producer_index = prod;

		smp_mb();
		wmb();

		if (unlikely(!test_bit(BNAD_TXQ_TX_STARTED, &tcb->flags)))
		return NETDEV_TX_OK;
		@@ -3102,7 +3103,6 @@ bnad_start_xmit(struct sk_buff skb, struct net_device netdev)
		skb_tx_timestamp(skb);

		bna_txq_prod_indx_doorbell(tcb);
		smp_mb();

		return NETDEV_TX_OK;
		}