On Mon, 21 Jul 2003, Daniel Ritz wrote: > On Mon July 21 2003 13:00, Javier Achirica wrote: > > > > Daniel, > > > > Thank you for your patch. Some comments about it: > > > > - I'd rather fix whatever is broken in the current code than going back to > > spinlocks, as they increase latency and reduce concurrency. In any case, > > please check your code. I've seen a spinlock in the interrupt handler that > > may lock the system. > > but we need to protect from interrupts while accessing the card and waiting for > completion. semaphores don't protect you from that. spin_lock_irqsave does. the > spin_lock in the interrupt handler is there to protect from interrupts from > other processors in a SMP system (see Documentation/spinlocks.txt) and is btw. > a no-op on UP. and semaphores are quite heavy.... Not really. You can still read the received packets from the card (as you're not issuing any command and are using the other BAP) while a command is in progress. There are some specific cases in which you need to have protection, and that cases are avoided with the down_trylock. AFAIK, interrupt serialization is assured by the interrupt handler, so you don't need to do that. > > - The fix for the transmit code you mention, is about fixing the returned > > value in case of error? If not, please explain it to me as I don't see any > > other changes. > > fixes: > - return values > - when to free the skb, when not > - disabling the queues > - netif_wake_queue called from the interrupt handler only (and on the right > net_device) > - i think the priv->xmit stuff and then the schedule_work is evil: > if you return 0 from the dev->hard_start_xmit then the network layer assumes > that the packet was kfree_skb()'ed (which does only frees the packet when the > refcount drops to zero.) this is the cause for the keventd killing, for sure! > > if you return 0 you already kfree_skb()'ed the packet. and that's it. This is where I have the biggest problems. As I've read in Documentation/networking/driver.txt, looks like the packet needs to be freed "soon", but doesn't require to be before returning 0 in hard_start_xmit. Did I get it wrong? Thanks for your help, Javier Achirica - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
