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

[Johannes Berg <johannes@sipsolutions.net>]

On Thu, 2012-12-13 at 09:46 -0800, Ben Greear wrote:
> As previously posted, there can be cases where the RTNL is held for a
> very long time when trying to do the:  flush_workqueue(local->workqueue);
> in mac80211_do_stop because there are lots of 'slow' work-items queued up.
> 
> I'd like to work on making this faster...
> 
> My first idea is to add a second work-queue to the 'local' for high-priority
> items that can be executed independently from the current local->workqueue,
> and put the free_sta_rcu work() in that queue.
> 
> I'm guessing that to be safe, the do_stop() code would need to selectively
> purge any work items in the local->workqueue that relate to the sdata
> being destroyed, as well.  I'm not sure how possible that would be...

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.

The only/easiest thing that seems vaguely safe would be a per-vif
workqueue for this? But that's really annoying too, since it needs an
extra thread etc.

johannes