Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway

Rafael J. Wysocki
2007-07-03T14:44:27Z

On Tuesday, 3 July 2007 16:21, Johannes Berg wrote:
> On Tue, 2007-07-03 at 14:56 +0200, Rafael J. Wysocki wrote:
>
> > Still, can you please read this post from Alan Stern:
> >
> > https://lists.linux-foundation.org/pipermail/linux-pm/2007-June/012847.html
> >
> > ? I don't think I'm able to repeat the arguments given in there in a
> > convincing way.
>
> As I read it, Alan basically has two objections:
> (1) drivers shouldn't need to worry about this
> (2) suspend should be transparent to userspace
>
> His proposed solution (freezing tasks when they cross the kernel
> boundary) helps for the s-t-r case, but in fact doesn't solve (1)
> because devices can be suspended at runtime

This is a different thing and a different infrastructure is needed for it (not
present at the moment).

> and then you certainly do not want to freeze tasks that try to access the
> device.
>
> (2) is related but not identical, what if you have a device suspended at
> runtime and some tasks tries to access it; should the task block until
> you wake up that device?

I think the device should be woken up in that case.

> I think the core of the discussion isn't appreciated by everybody here
> yet---we need to solve both run-time and suspend-to-ram-time device
> suspend, not just one of them.

For now, we're discussing the suspend-to-ram-time suspend only, for which
we have (some) infrastrcuture (and which should be supported by all drivers,
IMO).

Greetings,
Rafael

--
"Premature optimization is the root of all evil." - Donald Knuth