Re: [PATCH v3] ucc_geth: Lockless xmit

Joakim Tjernlund [off-list ref] :

Currently ucc_geth_start_xmit wraps IRQ off for the
whole body just to be safe. By rearranging the code a bit
one can avoid the lock completely.

Afaics you went a bit too lockless with the queueing disable / enable
logic. The hard_start_xmit handler is run in a locally softirq disabled
section but it will happily race with the napi handler on a different
CPU. Grep netif_tx_lock in tg3.c for it.

The Tx skb free logic probably requires some smp memory barriers as
well since the current skb is used by the ucc_geth driver to sync the
Tx xmit with the napi completion handler.

-- 
Ueimor