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

[Ben Greear <greearb@candelatech.com>]

On 12/13/2012 10:37 AM, Johannes Berg wrote:
> On Thu, 2012-12-13 at 10:30 -0800, Ben Greear wrote:
>> On 12/13/2012 10:24 AM, Johannes Berg wrote:
>>> On Thu, 2012-12-13 at 10:19 -0800, Ben Greear wrote:
>>>
>>>>> I don't think that's easy, but you're welcome to try. The
>>>>> free_sta_work() function references the sdata so it absolutely must run
>>>>> at this point.
>>>
>>>> So, cancel_work_sync(&sdata->work) would appear to remove
>>>> all pending sdata->work items from the work-queue.  As long as
>>>> there are no other different work items that reference
>>>> sdata (and maybe there are..I haven't looked at all of them),
>>>> then we should be safe to execute the free_sta_work()
>>>> on a different work-queue safely, I think....
>>>
>>> Sorry, I don't get it. free_sta_work() *itself* has to be executed
>>> before the sdata is destroyed. cancel_work_sync(&sdata->work) has
>>> nothing to do with free_sta_work.
>>
>> My concern is this:
>>
>> If I add a different work queue (called destructor-workqueue, perhaps)
>> for free_sta_work(), then it only helps
>> if I can not block on flushing the current 'big' work-queue.  But, if
>> there are items on the big work-queue that reference sdata, then
>> that could easily execute after free_sta_work(), and I'm guessing
>> that would be very bad.
>>
>> 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....

Thanks,
Ben


>
> johannes
>


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