On Tue, 2006-08-08 at 12:51 +1000, Herbert Xu wrote: > > 2. Eliminate the private tx_lock altogether and rely solely on > > netif_tx_lock. This eliminates one spinlock in tg3_start_xmit() > > when the ring is full. > > Why not get rid of the lock altogether? By making sure memory > barriers are present on the stop/wake paths the locks are not > needed anymore.
Without the lock, I think you can still wake the queue with an empty ring in some cases. Although we handle it properly by returning NETDEV_TX_BUSY, it is considered a BUG condition in tg3. > > > 4. Make tx_cons and tx_prod volatile to guarantee that > > tg3_start_xmit() and tg3_tx() will see the latest ring indices. > > Such uses of volatile are bad inside the kernel because they > don't actually provide hardware memory barriers and their effect > on the compiler are given by constructs such as mb() anyway. > Just trying to prevent the compiler from optimizing the code. In cases where we need hardware barriers we use mb. > So we should simply add memory barriers where needed. > I can do that. It will be more mb() scattered in the driver. Actually, I can probably hide it in the TX_BUFFS_AVAIL() macro. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
