Re: [PATCH] firmware: wake all waiters

[Davidlohr Bueso]

Hi Luis!

On Wed, 28 Jun 2017, Luis R. Rodriguez wrote:

> On Wed, Jun 28, 2017 at 06:45:14AM -0700, Davidlohr Bueso wrote:
> > On Tue, 27 Jun 2017, Luis R. Rodriguez wrote:
> >
> > > diff --git a/include/linux/swait.h b/include/linux/swait.h
> > > index 4a4e180d0a35..14fcf23cece4 100644
> > > --- a/include/linux/swait.h
> > > +++ b/include/linux/swait.h
> > > @@ -29,7 +29,10 @@
> > >  *
> > >  * As a side effect of this; the data structures are slimmer.
> > >  *
> > > - * One would recommend using this wait queue where possible.
> >
> > So I think this was added due to the smaller footprint and fewer
> > cycles that swait has compared to the traditional (bulkier)
> > waitqueues. While probably not worth it, I guess we could offer
> > super-simple waitqueues (sswait? :-) which do not have the rt caveats
> > and uses a regular spinlock. The wakeup_all() call would not drop
> > the lock upon every wakeup as we are stripping the waitqueue not
> > for determinism, but for overhead. To mitigate this, we might
> > also want to use wake_q for reduced hold q->lock hold times.
> >
> > But I don't think its worth yet another wait interface.
> > Alternatively, it crossed my mind we could also have wakeup_all()
> > use in the regular waitqueues, but I'd have to audit all the
> > current users to make sure we could actually do this.
>
> But this open-welcoming invite for swait then, should it go?

I have nothing against removing it.

Thanks,
Davidlohr