Re: Add a new work-queue for destructing stations?

[Ben Greear <greearb@candelatech.com>]

On 12/13/2012 10:41 AM, Johannes Berg wrote:
> On Thu, 2012-12-13 at 10:39 -0800, Ben Greear wrote:
>
>>>> So, near where we currently call cancel_work_sync(&sdata->work), I
>>>> think we'd also need to cancel things like the sta->ampdu_mlme.work,
>>>> and probably others as well.
>>>>
>>>> Then, when we're sure there are no more references to sdata on the
>>>> main-work-queue, it would be safe to flush the destructor-workqueue
>>>> (which would have the fre_sta_work() on it).
>>>>
>>>> Maybe?
>>>
>>> Huh, ok, but I don't think you'll find much that doesn't reference an
>>> sdata?
>>
>> I think you are right...so just need to find all of those work items
>> and call cancel_work_sync() on them, just like we are currently cancelling
>> the sdata->work....
>
> Well the concern there is that we expose the workqueue to the driver,
> and it might even put sdata-referencing work items on it and expect them
> to be flushed out before stop_interface() is called?
>
> You'd be welcome to change the API so that isn't true, or things are
> different, or whatever, but it'd be a lot of careful auditing (and
> probably fixing) of drivers.

So, maybe a new driver api call to 'cancel_all_work_items(sdata)',
and if the driver does not implement this, then we stick with the
full flush_workqueue() in mac80211_do_stop().  But, if the driver
does implement it, and we add code there to flush any mac80211 related
work-items, then we could skip the flush_workqueue() call....

I'll go looking in ath9k to see how much it uses the work-queue...that
driver is my only real concern at the moment.

Thanks,
Ben

>
> johannes
>


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