netdev - Re: [net-next 04/14] net: Fix issue with netdev_tx_reset_queue not resetting queue from XOFF state

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Date:	Sat, 21 Apr 2012 09:27:31 -0700
From:	John Fastabend <john.r.fastabend@...el.com>
To:	Tom Herbert <therbert@...gle.com>
CC:	Alexander Duyck <alexander.duyck@...il.com>,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	davem@...emloft.net, netdev@...r.kernel.org, gospo@...hat.com,
	sassmann@...hat.com
Subject: Re: [net-next 04/14] net: Fix issue with netdev_tx_reset_queue not
 resetting queue from XOFF state

On 4/20/2012 11:01 PM, Tom Herbert wrote:
>> I don't recall the exact reason now, as John said I think it had to do
>> with the ethtool tests not using the same cleanup routine and leaving
>> us in a bad state.  I am pretty sure there was some path in which
>> where the call was didn't work but I do not recall the exact details
>> now.  Most of the reason for moving it is due to the fact that the
>> reset is now also clearing the bit, and from the driver perspective we
>> didn't need it in two places.  After looking it all over again, I
>> suppose this causes a cosmetic issue for the bql "inflight" statistic
>> in sysfs since the value will be retained until the interface is
>> brought back up with this change.  Is that an issue or something that
>> can be lived with since the interface isn't active anyway in this
>> case?
>>
> On the surface, it seems cleaner and probably a simpler convention to
> clear the state when the buffers are being freed.  If there's a good
> reason not to do this for igb, it makes me wonder if this should be
> done the same way in other drivers...
> 
> Tom

Just dug up the old thread. This was to fix a bug that byte queue limits
was causing with some of the loopback tests evoked from ethtool. The
loopback test uses a separate path to free the buffers which wasn't
calling netdev_tx_reset_queue().

We should likely just explicitly clear the state in each routine rather
than try to be clever IMO.

.John


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