Re: [RFC] Implementation of SCSI dynamic power management

Oliver Neukum
2008-01-10T09:26:19Z

Am Mittwoch, 9. Januar 2008 21:36:20 schrieb Alan Stern:
> On Wed, 9 Jan 2008, Oliver Neukum wrote:
>
> > Am Mittwoch, 9. Januar 2008 18:22:51 schrieb Alan Stern:
> > > On Wed, 9 Jan 2008, Oliver Neukum wrote:
> > >
> > > > This has an interesting implication. As the storage driver can share
> > > > a device with in principle any other usb driver, we must audit all usb
> > > > drivers if we wish to adopt this patch.
> > > > All a device's interfaces must be resumed when the storage interface
> > > > is resumed. To resume a storage device no memory must be allocated
> > > > because that could deadlock.
> > >
> > > Maybe people shouldn't enable autosuspend for their swap device...
> >
> > Good advice, but not sufficient to avoid this problem. The vm may write
> > out normal dirty cached pages to scsi devices, which affects storage.
>
> For now, I think the best approach is "head-in-the-sand". There aren't
> a lot of USB storage devices partnered with other functions at the
> moment.

Very well with exception of the hub driver.

> But it might be a good idea for all USB drivers to use GFP_NOIO in
> their resume pathways.

Yes, we should make this a requirement for every driver henceforth changed
to support autosuspend.

Regards
Oliver