linux-kernel - Re: [PATCH] PCI: Move device_del() from pci_stop_dev() to pci_destroy

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Message-ID: <2101601.XbDHenBU6p@vostro.rjw.lan>
Date:	Mon, 25 Nov 2013 23:19:03 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tejun Heo <tj@...nel.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>
Subject: Re: [PATCH] PCI: Move device_del() from pci_stop_dev() to pci_destroy_dev()

On Monday, November 25, 2013 02:59:44 PM Bjorn Helgaas wrote:
> On Sat, Nov 23, 2013 at 5:17 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > After commit bcdde7e221a8 (sysfs: make __sysfs_remove_dir() recursive)
> > I'm seeing traces analogous to the one below in Thunderbolt testing:

[...]

> > (Mika Westerberg sees them too in his tests).
> >
> > Some investigation documented in kernel bug #65281 lead me to the
> > conclusion that the source of the problem is the device_del() in
> > pci_stop_dev() as it now causes the sysfs directory of the device
> > to be removed recursively along with all of its subdirectories.
> > That includes the sysfs directory of the device's subordinate
> > bus (dev->subordinate) and its "power" group.
> >
> > Consequently, when pci_remove_bus() is called for dev->subordinate
> > in pci_remove_bus_device(), it calls device_unregister(&bus->dev),
> > but at this point the sysfs directory of bus->dev doesn't exist any
> > more and its "power" group doesn't exist either.  Thus, when
> > dpm_sysfs_remove() called from device_del() tries to remove that
> > group, it triggers the above warning.
> >
> > That indicates a logical mistake in the design of
> > pci_stop_and_remove_bus_device(), which causes bus device objects
> > to be left behind their parents (bridge device objects) and can be
> > fixed by moving the device_del() from pci_stop_dev() into
> > pci_destroy_dev(), so pci_remove_bus() can be called for the
> > device's subordinate bus before the device itself is unregistered
> > from the hierarchy.  Still, the driver, if any, should be detached
> > from the device in pci_stop_dev(), so use device_release_driver()
> > directly from there.
> >
> > References: https://bugzilla.kernel.org/show_bug.cgi?id=65281#c6
> > Reported-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Applied to for-linus for v3.13.  Thanks a lot for all your work on this issue!

Thanks, and no problem! :-)

Rafael

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