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

[Alan Stern]

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

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