cxgb4: Fix race between loopback and normal Tx path

Even after Tx queues are marked stopped, there exists a
small window where the current packet in the normal Tx
path is still being sent out and loopback selftest ends
up corrupting the same Tx ring. So, ensure selftest takes
the Tx lock to synchronize access the Tx ring.

Fixes: 7235ffae3d2c ("cxgb4: add loopback ethtool self-test")
Signed-off-by: Ganji Aravind <ganji.aravind@chelsio.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/chelsio/cxgb4/sge.c b/drivers/net/ethernet/chelsio/cxgb4/sge.c
index 7c9fe4bc235bb7ced167043b7c363aa32c70b802..869431a1eedd482776bdd3a298883dc24aabfc67 100644 (file)
--- a/drivers/net/ethernet/chelsio/cxgb4/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/sge.c
@@ -2561,11 +2561,14 @@ int cxgb4_selftest_lb_pkt(struct net_device *netdev)
        lb->loopback = 1;
 
        q = &adap->sge.ethtxq[pi->first_qset];
+       __netif_tx_lock(q->txq, smp_processor_id());
 
        reclaim_completed_tx(adap, &q->q, -1, true);
        credits = txq_avail(&q->q) - ndesc;
-       if (unlikely(credits < 0))
+       if (unlikely(credits < 0)) {
+               __netif_tx_unlock(q->txq);
                return -ENOMEM;
+       }
 
        wr = (void *)&q->q.desc[q->q.pidx];
        memset(wr, 0, sizeof(struct tx_desc));
@@ -2598,6 +2601,7 @@ int cxgb4_selftest_lb_pkt(struct net_device *netdev)
        init_completion(&lb->completion);
        txq_advance(&q->q, ndesc);
        cxgb4_ring_tx_db(adap, &q->q, ndesc);
+       __netif_tx_unlock(q->txq);
 
        /* wait for the pkt to return */
        ret = wait_for_completion_timeout(&lb->completion, 10 * HZ);