Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

Alan Stern
2010-05-28T00:59:39Z

On Fri, 28 May 2010, Rafael J. Wysocki wrote:

> > And the forced-suspend design relies on the fact that processes remain
> > frozen throughout. If we leave some processes unfrozen and one of them
> > somehow becomes runnable, that means we have to abort the forced
> > suspend before the process is allowed to run.
>
> We could avoid that if drivers could block tasks, but there are questions to
> answer. First off, how a driver is supposed to know when to block the task
> using it and when to do its power management transparently for the task?
> Second, how to intercept and block all possible interfaces that user space
> can use to talk to drivers (how to intercept a task using mmapped device, for
> example)?

We talked about this a few years ago and decided it was not feasible.
It would require substantial changes to every device driver.

Alan Stern