Re: [RFC][PATCH -mm 1/7] PM: Remove pm_parent from struct dev_pm_info

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Monday, 11 June 2007 17:59, Alan Stern wrote:
> On Mon, 11 Jun 2007, Rafael J. Wysocki wrote:
> 
> > From: Rafael J. Wysocki <rjw@sisk.pl>
> > 
> > The pm_parent member of struct dev_pm_info (defined in include/linux/pm.h) is
> > only used to check if the device's parent is in the right state while the
> > device is being suspended or resumed.  However, this can be done just as well
> > with the help of the parent pointer in struct device, so pm_parent can be
> > removed along with some code that handles it.
> 
> > @@ -61,21 +40,26 @@ int device_pm_add(struct device * dev)
> >  		 kobject_name(&dev->kobj));
> >  	mutex_lock(&dpm_list_mtx);
> >  	list_add_tail(&dev->power.entry, &dpm_active);
> > -	device_pm_set_parent(dev, dev->parent);
> > -	if ((error = dpm_sysfs_add(dev)))
> > +	/*
> > +	 * The device's parent must not be released until the device itself is
> > +	 * removed from the dpm_active list.
> > +	 */
> > +	get_device(dev->parent);
> > +	error = dpm_sysfs_add(dev);
> > +	if (error)
> >  		list_del(&dev->power.entry);
> >  	mutex_unlock(&dpm_list_mtx);
> >  	return error;
> >  }
> 
> The error pathway here does an unbalanced get_device on dev->parent.
> 
> Anyway, I don't think you need to do this get_device at all (or the
> coresponding put in device_pm_remove).  As long as a device is
> registered it retains a reference to its parent, and unregistration
> always calls device_pm_remove.

Yes, I've just come to the same conclusion.  I'll remove the
get_device(dev->parent) and the correspondint put_device(dev->parent)
from device_pm_remove().

Greetings,
Rafael


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