Re: SRCU-based notifier chains

Paul E. McKenney
2006-07-11T18:21:37Z

On Tue, Jul 11, 2006 at 02:03:50PM -0400, Alan Stern wrote:
> On Tue, 11 Jul 2006, Paul E. McKenney wrote:
>
> > Looks sane to me. A couple of minor comments interspersed.
>
> Okay, I'll submit it with a proper writeup.
>
> > > +/*
> > > + * SRCU notifier chain routines. Registration and unregistration
> > > + * use a mutex, and call_chain is synchronized by SRCU (no locks).
> > > + */
> >
> > Hmmm... Probably my just failing to pay attention, but haven't noticed
> > the double-header-comment style before.
>
> As far as I know, I made it up. It seemed appropriate, since the first
> header applies to the entire group of three routines that follow whereas
> the second header is kerneldoc just for the next function.

Fair enough -- I missed the fact that the first header applies to
all three functions.

> > > /*
> > > - * Notifier chains are of three types:
> > > + * Notifier chains are of four types:
> >
> > Is it possible to subsume one of the other three types?
> >
> > Might not be, but have to ask...
>
> In principle we could replace blocking notifiers, but in practice we
> can't.
>
> We can't just substitute one for the other for two reasons: SRCU notifiers
> need special initialization which the blocking notifiers don't have, and
> SRCU notifiers have different time/space tradeoffs which might not be
> appropriate for all existing blocking notifiers.

Again, fair enough!

Thanx, Paul