Re: workqueue_drain

[Paul Goyette <paul%whooppee.com@localhost>]

On Wed, 20 Dec 2017, Michael van Elst wrote:

> ozaki-r%netbsd.org@localhost (Ryota Ozaki) writes:
>
> > On Wed, Dec 20, 2017 at 8:06 PM, Michael van Elst <mlelstv%serpens.de@localhost>
> >  wrote:
> > > What about a method that waits for a specific work to complete?
>
> > It might be useful but how it works in this case?
>
> You could remember the last work enqueued and wait for it to finish
> before destroying the queue. For this the wait function must handle
> the case where the work already has finished.

In the case of a WQ_PERCPU workqueue, this could be tricky.  The last
wor enqueued might be for an otherwise-idle CPU and could be finished
while somee other CPU(s) still have entries queued...

> I would consider such a function more versatile than just a drain
> function.

I'm not totally convinced here.  It might be useful to wait for a
particular work to be finished in order to allow it to be enqueued
again (no work can be enqueued if already in the queue).  But I don't
see how "remember the last work enqueued and wait for it to be done
before destroying" is more versatile than "waiting for all to be done
before destroying".  It certainly seems that the latter is a simpler
approach.


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