linux-kernel - Re: [PATCH][tentative] PCI / ACPI: Rework PCI host bridge removal to avoid sysfs warnings

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Date:	Mon, 30 Dec 2013 13:51:28 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH][tentative] PCI / ACPI: Rework PCI host bridge removal to avoid sysfs warnings

On Sunday, December 29, 2013 07:30:18 PM Yinghai Lu wrote:
> On Sat, Dec 28, 2013 at 3:20 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > The device_del(&host_bridge->dev) in pci_stop_root_bus() is
> > problematic, because it causes all sysfs directories below
> > the host bridge to be removed recursively and when
> > pci_remove_root_bus() attempts to remove devices on the root
> > bus (whose sysfs directories are gone now along with all their
> > subdirectories), it causes warnings similar to this one to be
> > printed:
> >
> > WARNING: CPU: 0 PID: 6 at fs/sysfs/group.c:214 sysfs_remove_group+0xc6/0xd0()
> > sysfs group ffffffff819ac5c0 not found for kobject '0001:ff:10.2'
> > Modules linked in: <irrelevant list>
> > CPU: 0 PID: 6 Comm: kworker/u512:0 Tainted: G        W    3.13.0-rc5+ #11
> > Hardware name:
> > Workqueue: kacpi_hotplug acpi_hotplug_work_fn
> >  0000000000000009 ffff8808738d3bd8 ffffffff815d84ea ffff8808738d3c20
> >  ffff8808738d3c10 ffffffff8106594d 0000000000000000 ffffffff819ac5c0
> >  ffff880871b9d0a8 ffff8a07d1895000 0000000000000103 ffff8808738d3c70
> > Call Trace:
> >  [<ffffffff815d84ea>] dump_stack+0x45/0x56
> >  [<ffffffff8106594d>] warn_slowpath_common+0x7d/0xa0
> >  [<ffffffff810659bc>] warn_slowpath_fmt+0x4c/0x50
> >  [<ffffffff8122b52e>] ? sysfs_get_dirent_ns+0x4e/0x70
> >  [<ffffffff8122c806>] sysfs_remove_group+0xc6/0xd0
> >  [<ffffffff813b83f3>] dpm_sysfs_remove+0x43/0x50
> >  [<ffffffff813ae105>] device_del+0x45/0x1c0
> >  [<ffffffff812e51f6>] pci_remove_bus_device+0x66/0xd0
> >  [<ffffffff812e5363>] pci_remove_root_bus+0x73/0x80
> >  [<ffffffff813276ab>] acpi_pci_root_remove+0x42/0x4f
> >  [<ffffffff81323070>] acpi_bus_trim+0x56/0x89
> >  [<ffffffff81323052>] acpi_bus_trim+0x38/0x89
> >  [<ffffffff813245df>] acpi_device_hotplug+0x137/0x33b
> >  [<ffffffff8131efba>] acpi_hotplug_work_fn+0x1c/0x27
> >  [<ffffffff81080f1b>] process_one_work+0x17b/0x460
> >  [<ffffffff81081ccb>] worker_thread+0x11b/0x400
> >  [<ffffffff81081bb0>] ? rescuer_thread+0x3e0/0x3e0
> >  [<ffffffff81088a12>] kthread+0xd2/0xf0
> >  [<ffffffff81088940>] ? kthread_create_on_node+0x180/0x180
> >  [<ffffffff815e823c>] ret_from_fork+0x7c/0xb0
> >  [<ffffffff81088940>] ? kthread_create_on_node+0x180/0x180
> >
> > To avoid that, the host bridge device has to be deleted after all of
> > its children, so merge pci_stop_root_bus() and pci_remove_root_bus()
> > into one function, pci_stop_and_remove_root_bus(), that first will
> > use pci_stop_and_remove_bus_device() to stop and remove all devices
> > on the root bus and then will delete the host bridge device, remove
> > its bus and drop the final reference to it.
> >
> > Reported-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >
> > Hi,
> >
> > I can't really test this patch, but I don't know how it can break anything.
> >
> > The only user of pci_stop_root_bus() and pci_remove_root_bus() is
> > acpi_pci_root_remove() and the code ordering there seems to be somewhat
> > arbitrary.  If you are aware of any reason why it may not work, please let
> > me know. :-)
> >
> > Thanks,
> > Rafael
> >
> > ---
> >  drivers/acpi/pci_root.c |    4 +---
> >  drivers/pci/remove.c    |   23 ++++-------------------
> >  include/linux/pci.h     |    3 +--
> >  3 files changed, 6 insertions(+), 24 deletions(-)
> >
> > Index: linux-pm/drivers/acpi/pci_root.c
> > ===================================================================
> > --- linux-pm.orig/drivers/acpi/pci_root.c
> > +++ linux-pm/drivers/acpi/pci_root.c
> > @@ -611,12 +611,10 @@ static void acpi_pci_root_remove(struct
> >  {
> >         struct acpi_pci_root *root = acpi_driver_data(device);
> >
> > -       pci_stop_root_bus(root->bus);
> > -
> >         device_set_run_wake(root->bus->bridge, false);
> >         pci_acpi_remove_bus_pm_notifier(device);
> >
> > -       pci_remove_root_bus(root->bus);
> > +       pci_stop_and_remove_root_bus(root->bus);
> >
> >         kfree(root);
> >  }
> 
> 
> We have patches that need to stop ioapic and iommu between
> pci_stop_root_bus and pci_remove_root_bus.
> 
> Please check if the problem still happen after
> 
> http://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/patch/?id=c4a0a5d964e90b93eb4101c3927b788e083e530f
> 
> http://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/patch/?id=e3b439e1d315aff59c1b4f0fc43c5cd2d82b4138

The second one should fix the problem.

Thanks,
Rafael

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