Re: [RFC][PATCH] PM: Make PM core handle device registrations concurrent with suspend/hibernation

[Alan Stern <stern@rowland.harvard.edu>]

On Thu, 6 Mar 2008, Rafael J. Wysocki wrote:

> > I thought of one more thing you might want to add: device_pm_add() 
> > doesn't handle the case where dev->parent is NULL.
> 
> I'm not sure what you mean.
> 
> If dev->parent is NULL, we get into the "successful" branch where the device is
> added to dpm_active.  Do you think we should add any extra handling of this
> case?

If a device is registered after dpm_suspend() has returned, the
device won't be suspended properly before the system goes to sleep.  

If the device has a parent then you're okay, because the parent must
already be suspended and so device_pm_add() will fail.  But if the
device doesn't have a parent then device_pm_add() will succeed, which
you don't want.

> > You could put in that static "all_devices_sleeping" flag, which gets set at
> > the end of dpm_suspend() and cleared at the start of dpm_resume().
> 
> Well, I don't think it's necessary.  dpm_active is empty in that case and
> we can use the list_empty(&dpm_active) check instead.

What would happen the very first time the system registers a device 
during startup?

Alan Stern