Panic with wifi + usb in latest FreeBSD-current

[Kevin Oberman]

Small correction... My rtwn is running at 1 MB, not Mb. I have two tools
watching the network, one does bits and the other bytes. Still,
performance is really bad. Can't say whether it's the driver or something
else, but I'll be gathering data as I can between reboots of my current
system.

Sorry for the bogus information.
--
Kevin Oberman, Part time kid herder and retired Network Engineer
E-mail: rkoberman at gmail.com
PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683


On Mon, Sep 14, 2020 at 9:52 AM Kevin Oberman <rkoberman at gmail.com> wrote:

> On Sun, Sep 13, 2020 at 11:31 PM Adrian Chadd <adrian.chadd at gmail.com>
> wrote:
>
>> On Sun, 13 Sep 2020 at 22:34, Warner Losh <imp at bsdimp.com> wrote:
>>
>> >
>> >
>> > On Sun, Sep 13, 2020, 11:29 PM Adrian Chadd <adrian.chadd at gmail.com>
>> > wrote:
>> >
>> >> Yeah, this was also reported in #freebsd-wireless today.
>> >>
>> >> Is there a lock being held in the rtwn path that shouldn't be?
>> >>
>> >
>> > I'll check in the morning... this was like the 20th thing to go wrong
>> this
>> > weekend,  so I copied the panic down, send the email and grabbed a beer
>> and
>> > turned it off...
>> >
>>
>> Ok. I checked the driver and the usb stack; nothing in the change lists
>> obviously stands out to me at 11pm on a Sunday.
>>
>> Can you see if any locks are held? or an epoch? Something smells fishy.
>> (defining EPOCH_TRACE will dump the list of epochs, if I'm reading the
>> subr_sleepqueue.c code correctly.)
>>
>> Ok, so, since I dug a bit more on a hunch, I bet the NET epoch is being
>> held - it's grabbed in rtwn_bulk_rx_callback, and rtwn_rx_common is
>> reading
>> some registers as part of processing the receive queue. I bet that act of
>> reading registers over blocking USB is causing things to explode.
>>
>> If it is net epoch then we're going to have to think of a better design
>> pattern here to migrate all of these here wifi drivers to, because I
>> guarantee you they're all behaving poorly in this newer world order.
>>
>>
>>
>> Thanks,
>>
>>
>> -adrian
>>
> While I have not seen panics, performance of my rtwn has simply cratered.
> Trying to move files to my new laptop, which has an rtwn, it crawls at
> about 1.5 Mbps. Before I built an updated kernel, I was seeing 60M. Of
> course, this is complicated by the continual kernel lockups I keep getting,
> so I really didn't think much about it until I saw Warner's note.
> --
> Kevin Oberman, Part time kid herder and retired Network Engineer
> E-mail: rkoberman at gmail.com
> PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683
>
>