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SubjectRe: Async suspend-resume patch w/ completions (was: Re: Async suspend-resume patch w/ rwsems)
On Tue, 15 Dec 2009, Linus Torvalds wrote:

> My whole point was that by doing the whole "wait for children" in generic
> code, you also made devices - such as PCI bridges - have to wait for
> children, even though they don't need to, and don't want to.
>
> So I suggested an admittedly ugly hack to take care of it - rather than
> some complex infrastructure.

It doesn't feel like an ugly hack to me. It seems like exactly the
Right Thing To Do: Make as many devices as possible use async
suspend/resume.

The only reason we don't make every device async is because we don't
know whether it's safe. In the case of PCI bridges we _do_ know --
because they don't have any work to do outside of
late_suspend/early_resume -- and so they _should_ be async.

The same goes for devices that don't have suspend or resume methods.

There remains a separate question: Should async devices also be forced
to wait for their children? I don't see why not. For PCI bridges it
won't make any significant difference. As long as the async code
doesn't have to do anything, who cares when it runs?

Alan Stern



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