Re: Towards eliminating the freezer

Alan Stern
2007-07-24T22:14:20Z

On Tue, 24 Jul 2007, Rafael J. Wysocki wrote:

> > Then device_suspend() can be simplified:
> >
> > int device_suspend(pm_message_t state)
> > {
> > int error = 0;
> >
> > might_sleep();
> > list_for_each_entry_reverse(dev, &dpm_locked, power.entry) {
> > error = suspend_device(dev, state);
> >
> > if (error) {
> > printk(KERN_ERR "Could not suspend device %s: "
> > "error %d%s\n",
> > kobject_name(&dev->kobj), error,
> > error == -EAGAIN ? " (please convert to suspend_late)" : "");
> > break;
> > }
> > list_move(&dev->power.entry, &dpm_off);
>
> Is that safe with list_for_each_entry_reverse?

No. I guess it'll have to resemble the other code.

> Yes, that looks fine.
>
> So, who's writing the patch? ;-)

I can do it. You haven't made any changes to this part of the code,
have you? My work tends to be based on Linus's tree, not -mm.

Something to watch out for: With all the extra locking, we run the risk
of blocking the keventd workqueue. This may or may not matter, but to
be safe perhaps there should be a new general-purpose workqueue which
_expects_ to block (or freeze) during suspends. Any work routine that
involves adding or removing a device should go on the new workqueue.

> > Incidentally, what is dpm_mtx for? It doesn't seem to do anything
> > useful. Is it a relic of the former runtime PM support?
>
> I think so. IMO it can be removed.
>
> I also think it would be nicer to have all of the functions in
> drivers/base/power/{main|suspend|resume}.c moved to one file.

Yes, they are all similar enough that there isn't much point keeping
them separate.

Alan Stern