net: txq_trans_update() helper

We would like to get rid of netdev->trans_start = jiffies; that about all net
drivers have to use in their start_xmit() function, and use txq->trans_start
instead.

This can be done generically in core network, as suggested by David.

Some devices, (particularly loopback) dont need trans_start update, because
they dont have transmit watchdog. We could add a new device flag, or rely
on fact that txq->tran_start can be updated is txq->xmit_lock_owner is
different than -1. Use a helper function to hide our choice.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ae3c2099a04b..586b71f0358c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1674,6 +1674,12 @@ static inline void __netif_tx_unlock_bh(struct netdev_queue *txq)
         spin_unlock_bh(&txq->_xmit_lock);
 }
 
+static inline void txq_trans_update(struct netdev_queue *txq)
+{
+        if (txq->xmit_lock_owner != -1)
+                txq->trans_start = jiffies;
+}
+
 /**
  *      netif_tx_lock - grab network device transmit lock
  *      @dev: network device