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Message-Id: <200706112052.32872.rjw@sisk.pl>
Date: Mon, 11 Jun 2007 20:52:32 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Alan Stern <stern@...land.harvard.edu>
Cc: pm list <linux-pm@...ts.linux-foundation.org>,
David Brownell <david-b@...bell.net>, Greg KH <greg@...ah.com>,
LKML <linux-kernel@...r.kernel.org>, Pavel Machek <pavel@....cz>,
USB development list <linux-usb-devel@...ts.sourceforge.net>
Subject: Re: [RFC][PATCH -mm 1/7] PM: Remove pm_parent from struct dev_pm_info
On Monday, 11 June 2007 17:59, Alan Stern wrote:
> On Mon, 11 Jun 2007, Rafael J. Wysocki wrote:
>
> > From: Rafael J. Wysocki <rjw@...k.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
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