iflib tx watchdog doesn't appear that it can work anymore

[Ryan Stone]

We hit the bug of the watchdog firing on idle NICs and were working on
merging r356310 into our tree when we noticed the problem through code
inspection.  I don't think that it's really a bug with r356310, just a
latent one that has become exposed.

On Mon, Nov 9, 2020 at 2:48 PM Eric Joyner <erj at freebsd.org> wrote:
>
> I'll add Piotr, the author of your linked patch, to this thread.
>
> Are you seeing a problem connected to the watchdog? Piotr tells me that IFLIB_QUEUE_WORKING isn't used now, but it wasn't even used before his patch.
>
> - Eric
>
> On Wed, Nov 4, 2020 at 8:47 AM Ryan Stone <rysto32 at gmail.com> wrote:
>>
>> https://svnweb.freebsd.org/base?view=revision&revision=356310
>>
>> As of r356310, there does not appear to be a way that ift_qstatus can
>> be set to anything but IFLIB_QUEUE_IDLE.  As a result, I don't see
>> that there is any way for the watchdog to ever fire.
>>
>> I think that iflib has missed setting ift_qstatus to
>> IFLIB_QUEUE_WORKING when packets are enqueued on the rx ring.
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