linux-kernel - Re: [RFC PATCH v2, part3 07/11] PCI, xen-pcifront: use new PCI interfaces to simplify implementation

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Date:	Fri, 14 Jun 2013 14:07:19 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Jiang Liu <liuj97@...il.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	"Rafael J . Wysocki" <rjw@...k.pl>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Gu Zheng <guz.fnst@...fujitsu.com>,
	Toshi Kani <toshi.kani@...com>,
	Myron Stowe <myron.stowe@...hat.com>,
	Yijing Wang <wangyijing@...wei.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	xen-devel@...ts.xensource.com,
	virtualization@...ts.linux-foundation.org
Subject: Re: [RFC PATCH v2, part3 07/11] PCI, xen-pcifront: use new PCI
 interfaces to simplify implementation

On Tue, Jun 11, 2013 at 01:08:14AM +0800, Jiang Liu wrote:
> On Tue 11 Jun 2013 12:58:01 AM CST, Konrad Rzeszutek Wilk wrote:
> > On Mon, Jun 10, 2013 at 12:50:46AM +0800, Jiang Liu wrote:
> >> On Sat 08 Jun 2013 01:07:06 AM CST, Konrad Rzeszutek Wilk wrote:
> >>> On Sat, Jun 08, 2013 at 12:50:31AM +0800, Jiang Liu wrote:
> >>>> On 06/07/2013 11:38 PM, Konrad Rzeszutek Wilk wrote:
> >>>>> On Fri, Jun 07, 2013 at 10:50:24AM -0400, Konrad Rzeszutek Wilk wrote:
> >>>>>> On Thu, May 16, 2013 at 11:50:55PM +0800, Jiang Liu wrote:
> >>>>>>> Use new PCI interfaces to simplify xen-pcifront implementation:
> >>>>>>> 1) Use pci_create_root_bus() instead of pci_scan_bus_parented()
> >>>>>>>    because pci_scan_bus_parented() is marked as __deprecated.This
> >>>>>>>    also gets rid of a duplicated call of pci_bus_start_devices().
> >>>>>>> 2) Use pci_stop_root_bus() and pci_remove_root_bus() instead of
> >>>>>>>    open-coded private implementation.
> >>>>>>> 3) Use pci_set_host_bridge_release() to release data structures
> >>>>>>>    associated with PCI root buses.
> >>>>>>> 4) Use pci_bus_get()/pci_bus_put() to manage PCI root bus reference
> >>>>>>>    count.
> >>>>>>>
> >>>>>>> This is also a preparation for coming PCI bus lock enhancement.
> >>>>>
> >>>>> With this patch from :
> >>>>>
> >>>>>  Merge branch 'pci_lock_v3' of https://github.com/jiangliu/linux into testing
> >>>>>
> >>>>>
> >>>>> it blows up when detaching the device.
> >>>> Hi Konrad,
> >>>>    Thanks for testing! According to the log messages, this issue should
> >>>> be related to pci bus reference counter management. Seems we have done
> >>>> an extra(unbalanced) release of pci bus device.
> >>>>    Will investigate it tomorrow!
> >>>
> >>> That is quite commendable that you are willing to look over this on
> >>> the weekend but I am not going to be able to rerun this test until
> >>> some time in the week. You could enjoy the weekend and just look at
> >>> this during the week.
> >>
> >> Hi Konrad,
> >>      We should have root-caused this bug, which is caused by
> >> for_each_pci_root_bus().
> >> Current implementation doesn't support root bus deletion when walking
> >> PCI root
> >> buses by for_each_pci_root_bus(). The reference counter
> >> (pci_bus->dev.knode_class.n_ref)
> >> becomes zero after returning from pci_remove_root_bus(), so it triggers
> >> kref warnings
> >> and double-free of klist_node object when we call
> >> pci_get_next_root_bus() to get the
> >> next PCI root bus.
> >>      So we will first revert to  list_for_each_entry_safe(bus, temp,
> >> &pci_root_buses, node)
> >> and solve this issue in next version of for_each_pci_root_bus().
> >
> > That definitly solves the issue. Thanks!
> >
> > I used pci_lock_v3 of https://github.com/jiangliu/linux and the fix
> > below.
> >
> > Is there a new patchset you are going to be posting or a git branch
> > that I can look over?
> >
> > Thanks.
> Hi Konrad,
>      Really appreciate your support! I will try to post a new version 
> tomorrow,
> but I think there won't be big changes except addressing some review
> comments from you.

I also get this:

ERROR: "pci_set_host_bridge_release" [drivers/pci/xen-pcifront.ko] undefined!
ERROR: "pci_create_root_bus" [drivers/pci/xen-pcifront.ko] undefined!
ERROR: "pci_remove_root_bus" [drivers/pci/xen-pcifront.ko] undefined!
ERROR: "pci_stop_root_bus" [drivers/pci/xen-pcifront.ko] undefined!

when building it as a module.
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