Hard lockup during vif restart tests.

Ben Greear greearb at candelatech.com
Thu Sep 18 09:06:41 PDT 2014

On 09/18/2014 12:31 AM, Kalle Valo wrote:
> Michal Kazior <michal.kazior at tieto.com> writes:
>>> Why do we reset the firmware/NIC when we admin down/up the
>>> vif (when a single vif is active)?  Couldn't we just keep
>>> the firmware active in this state and not risk lockup due
>>> to reset?
>> If you put down last interface mac80211 calls drv_stop(). There isn't
>> any real need to keep the device up and running after that other than
>> trying to workaround the reset issue. But then you need to deal with
>> firmware quirks. I recall it could report Rx indications after all
>> vdevs had been removed (and this is now also observable with 10.2
>> during probing/bootup). It's just simpler to reboot firmware on
>> drv_stop/start().
> And there's the reliability issue. Being able to reset the firmware with
> interface down/up sequency is pretty useful and AFAIK almost all
> upstream drivers do that. And let's not forget power consumption either.

The fact that restarting firmware can hang the machine or require
reboot to recover is so serious that I think a work-around is
worth looking into.


Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

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