Messages in this thread | | | Date | Thu, 8 Apr 2004 09:06:33 -0500 | From | Matt Mackall <> | Subject | Re: [PATCH 2.6] netpoll: prevent transmission stall |
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On Thu, Apr 08, 2004 at 12:39:25PM +0200, Stelian Pop wrote: > While working on kgdb over netpoll I found out another bug in > netpoll. > > This one is in netpoll_send_skb(), and it is triggered by > sending repeatedly more packets than the transmit buffers the > ethernet card has, while being in the netpoll_trap. (this is > rapidly triggered by kgdb when using a card with limited > transmit buffers, like my pcmcia NE2000). > > One should poll() the ethernet card interrupt function in order > to get the transmit acks from the card and free the transmit > buffers in order to be able to transmit more packets. > > This is why in the original code, netpoll_send_skb() calls > netpoll_poll() if dev->hard_start_xmit() fails. However, this > does not work because netpoll_poll() is called only if > netif_queue_stopped(). But the net queue functions are overridden > if netpoll_trap() is on, causing netif_queue_stopped() to never > return true. > > The attached patch 'fixes' this, by forcing a netpoll_poll() > every time dev->hard_start_xmit() fails. Maybe there is a cleaner > way to do this by making the queue functions work even under > netpoll_trap, but it shouldn't really be necessary, I cannot > see how forcing the netpoll_poll() call could break anything.
Ok, makes sense. I'll queue this up.
-- Matt Mackall : http://www.selenic.com : Linux development and consulting - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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