Hello.
Amit S. Kale wrote:
>>>This driver's 4-packet deep TX queue is too sensible to the "careless"
>>>callers ignoring its state (like netpoll in trapped mode), so add "queue
>>>full" check at the start of the hard_start_xmit() method (only under
>>>#ifndef RTL8139_NDEBUG, otherwise the queue will get stuck once dirty
>>>pointer gets out of sync); switch to using appropriate mnemonics for the
>>>return values while at it.
>>Could you please describe this netpoll scenario in more detail?
>>More importantly, why wouldn't we fix netpoll instead?
> We're trying to figure out a way of fixing netpoll. Don't know what the
> solution is yet.
> Here is what happens: in KGDB we set netpoll trapped flag. This prevents
> stopping and starting of a netdev queue. Interfaces that have a small ring
> (8139) run into a problem because of this. When the ring goes full, it can't
> stop the queue. This doesn't make sense since in absence of ring descriptors,
> the device can't transmit any more packets. Sergie had posted one more patch
> last week that lets us start and stop queues in trapped state.
>
> This patch fixes the 8139 side behavior in this context.
Not really -- the patch doesn't seem necessary in this context. It's just
an attempt to make the driver more robust against out-of-sync dirty pointer
and posting packets to already stopped queue -- that check constituting the
second part is still necessary in certain out-of-sync pointer situation where
the queue may erroneously be woken up, i.e. with the difference between the
dirty_tx and cur_tx is multiple of 4 by the end of loop (well, I guess that
has happened only with netpoll in trapped mode so far). Remember that all
these checks are done only when the driver debugging is enabled (it *is*
enabled by default though).
> -Amit
MBR, Sergei
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