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

[Ben Greear <greearb@candelatech.com>]

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?

Thanks,
Ben


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