Re: [GIT PULL] PM updates for 2.6.33

Alan Stern
2009-12-07T22:01:08Z

On Mon, 7 Dec 2009, Linus Torvalds wrote:

> On Mon, 7 Dec 2009, Alan Stern wrote:
> >
> > It only seems that way because you didn't take into account devices
> > that suspend synchronously but whose children suspend asynchronously.
>
> But why would I care? If somebody suspends synchronously, then that's what
> he wants.

It doesn't mean he wants to block unrelated devices from suspending
asynchronously, merely because they happen to come earlier in the list.

> > A synchronous suspend routine for a device with async child suspends
> > would have to look just like your usb_node_suspend():
>
> Sure. But that sounds like a "Doctor, it hurts when I do this" situation.
> Don't do that.
>
> Make the USB host controller do its suspend asynchronously. We don't
> suspend PCI bridges anyway, iirc (but I didn't actually check). And at
> worst, we can make the PCI _bridges_ know about async suspends, and solve
> it that way - without actually making any normal PCI drivers do it.

This sounds suspiciously like pushing the problem up a level and
hoping it will go away. (Sometimes that even works.)

In the end it isn't a very big issue. Using one vs. two passes in
dpm_suspend() is pretty unimportant.

Alan Stern

P.S.: In fact I planned all along to handle USB host controllers
asynchronously anyway, since their resume routines contain some long
delays. I was merely using them as an example.