Re: [PATCH net 1/4] bnxt: don't lock the tx queue from napi poll

On Wed, 11 Aug 2021 13:42:40 -0700 Michael Chan wrote:

quoted

-       if (unlikely(netif_tx_queue_stopped(txq)) &&
-           (bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh)) {
-               __netif_tx_lock(txq, smp_processor_id());
-               if (netif_tx_queue_stopped(txq) &&
-                   bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh &&
-                   txr->dev_state != BNXT_DEV_STATE_CLOSING)
-                       netif_tx_wake_queue(txq);
-               __netif_tx_unlock(txq);
-       }
+       if (netif_tx_queue_stopped(txq) &&
+           bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh &&
+           READ_ONCE(txr->dev_state) != BNXT_DEV_STATE_CLOSING)  

This can race with bnxt_start_xmit().  bnxt_start_xmit() can also wake
up the queue when it sees that descriptors are available.  I think
this is the reason we added tx locking here.  The race may be ok
because in the worst case, we will wake up the TX queue when it's not
supposed to wakeup.  If that happens, bnxt_start_xmit() will return
NETDEV_TX_BUSY and stop the queue again when there are not enough TX
descriptors.

Good point, let me remove the warning from patch 3, then.