Re: Async resume patch (was: Re: [GIT PULL] PM updates for 2.6.33)

Alan Stern
2009-12-08T20:43:55Z

On Tue, 8 Dec 2009, Rafael J. Wysocki wrote:

> > This is a little more awkward because it requires the parent to iterate
> > through its children.
>
> I can live with that.
>
> > But it does solve the off-tree dependency problem for suspends.
>
> That's a plus, but I still think we're trying to create a barrier-alike
> mechanism using lock.
>
> There's one more possibility to consider, though. What if we use a completion
> instead of the flag + wait queue? It surely is a standard synchronization
> mechanism and it seems it might work here.

You're right. I should have thought of that. Linus's original
approach couldn't use a completion because during suspend it needed to
make one task (the parent) wait for a bunch of others (the children).
But if you iterate through the children by hand, that objection no
longer applies.

Alan Stern