On Wed, Dec 20, 2017 at 4:57 PM, Paul Goyette <p...@whooppee.com> wrote: > On Wed, 20 Dec 2017, Ryota Ozaki wrote: > >> Hi, >> >> workqueue_destroy requires that its queue doesn't have >> any works (and no new work will be enqueued anymore) >> before being called. Currently users of workqueue have >> to ensure the contract by theirselves. It's possible >> but it may need to add extra synchronization mechanisms >> such as mutex and condvar only for that purpose. >> >> workqueue itself can provide an API to help the routine. >> It, say workqueue_drain, waits for all pending works to >> finish. With it the caller needs to only ensure that no >> new work will be enqueued. >> >> Here is a patch: >> http://www.netbsd.org/~ozaki-r/workqueue_drain.diff >> (I will update workqueue.4 once the proposal is accepted.) >> >> And this is a patch that applies workqueue_drain to bridge(4): >> http://www.netbsd.org/~ozaki-r/workqueue_drain-example.diff >> >> If we don't have workqueue_drain we had to add an extra >> condvar to wait the workqueue worker of bridge to finish. >> >> Any comments or suggestions? > > > You could add a new flag bit for WQ_DRAINING when you start to > drain. Then workqueue_enque() could enforce the "no new work" > with > > KASSERT_MSG((wq->wg_flags & WQ_DRAINING) != 0, > "adding work to a draining workqueue")
Good idea! I updated the patch: http://www.netbsd.org/~ozaki-r/workqueue_drain.v2.diff Thanks, ozaki-r
