RE: [PATCH] NET: Multiqueue network device support.

I thought the correct use is to get this lock on clean_tx 
side which can get called on a different cpu on rx (which 
also cleans up slots for skbs that have finished xmit). Both 
TX and clean_tx uses the same tx_ring's head/tail ptrs and 
should be exclusive. But I don't find clean tx using this 
lock in the code, so I am confused :-)

From e1000_main.c, e1000_clean():

        /* e1000_clean is called per-cpu.  This lock protects
         * tx_ring[0] from being cleaned by multiple cpus
         * simultaneously.  A failure obtaining the lock means
         * tx_ring[0] is currently being cleaned anyway. */
        if (spin_trylock(&adapter->tx_queue_lock)) {
                tx_cleaned = e1000_clean_tx_irq(adapter,
                                                &adapter->tx_ring[0]);
                spin_unlock(&adapter->tx_queue_lock);
        }

In a multi-ring implementation of the driver, this is wrapped with for
(i = 0; i < adapter->num_tx_queues; i++) and &adapter->tx_ring[i].  This
lock also prevents the clean routine from stomping on xmit_frame() when
transmitting.  Also in the multi-ring implementation, the tx_lock is
pushed down into the individual tx_ring struct, not at the adapter
level.

Cheers,

-PJ Waskiewicz
peter.p.waskiewicz.jr@intel.com