Re: 3.3.0-rc5: OOps in dql_completed (Broadcom tg3 driver)

From: Tom Herbert
Date: Fri Mar 02 2012 - 12:23:21 EST


Hi Christoph, Eric,

Looks like we're hitting BUG_ON(count > dql->num_queued -
dql->num_completed). This is indicative of mis-accounting occurring
between netdev_sent_queue and netdev_completed_queue. I don't
immediately see how this could happen here in the tg3_tso_bug path,
this is still using the same calls to transmit and complete as other
paths. I suppose it's possible that skb_gso_segment is somehow
munging skb->len in segments.

I'll try to reproduce this.

> In case we hit BQL limit in one of the tg3_start_xmit() calls, we should
> 'abort' the following ones, dont you think ?

I'm not sure what you mean Eric. It should be okay to exceed the BQL
limit up to the point that num_queued rolls over (probably should be a
BUG_ON for that). This is a much greater number than could ever be
queued to tg3.

Thanks,
Tom

>
> Or maybe thats irrelevant, and only dql_queued() comment is wrong.
>
> Thanks
>
>
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