Re: [ 02/38] PCI/PM: Fix deadlock when unbinding device if parentin D3cold

[Huang Ying]

On Fri, 2012-11-30 at 10:54 +0800, Huang Ying wrote:
> On Thu, 2012-11-29 at 18:01 -0800, Greg Kroah-Hartman wrote:
> > On Fri, Nov 23, 2012 at 03:47:42PM +0800, Huang Ying wrote:
> > > On Fri, 2012-11-23 at 11:09 +0800, Huang Ying wrote:
> > > > On Fri, 2012-11-23 at 02:35 +0000, Ben Hutchings wrote:
> > > > > On Wed, 2012-11-21 at 16:39 -0800, Greg Kroah-Hartman wrote:
> > > > > > 3.0-stable review patch.  If anyone has any objections, please let me know.
> > > > > > 
> > > > > > ------------------
> > > > > > 
> > > > > > From: Huang Ying <ying.huang@xxxxxxxxx>
> > > > > > 
> > > > > > commit 90b5c1d7c45eeb622302680ff96ed30c1a2b6f0e upstream.
> > > > > > 
> > > > > > If a PCI device and its parents are put into D3cold, unbinding the
> > > > > > device will trigger deadlock as follow:
> > > > > > 
> > > > > > - driver_unbind
> > > > > >   - device_release_driver
> > > > > >     - device_lock(dev)				<--- previous lock here
> > > > > >     - __device_release_driver
> > > > > >       - pm_runtime_get_sync
> > > > > >         ...
> > > > > >           - rpm_resume(dev)
> > > > > >             - rpm_resume(dev->parent)
> > > > > >               ...
> > > > > >                 - pci_pm_runtime_resume
> > > > > >                   ...
> > > > > >                   - pci_set_power_state
> > > > > >                     - __pci_start_power_transition
> > > > > >                       - pci_wakeup_bus(dev->parent->subordinate)
> > > > > >                         - pci_walk_bus
> > > > > >                           - device_lock(dev)	<--- deadlock here
> > > > > > 
> > > > > > 
> > > > > > If we do not do device_lock in pci_walk_bus, we can avoid deadlock.
> > > > > > Device_lock in pci_walk_bus is introduced in commit:
> > > > > > d71374dafbba7ec3f67371d3b7e9f6310a588808, corresponding email thread
> > > > > > is: https://lkml.org/lkml/2006/5/26/38.  The patch author Zhang Yanmin
> > > > > > said device_lock is added to pci_walk_bus because:
> > > > > > 
> > > > > >   Some error handling functions call pci_walk_bus. For example, PCIe
> > > > > >   aer. Here we lock the device, so the driver wouldn't detach from the
> > > > > >   device, as the cb might call driver's callback function.
> > > > > > 
> > > > > > So I fixed the deadlock as follows:
> > > > > > 
> > > > > > - remove device_lock from pci_walk_bus
> > > > > > - add device_lock into callback if callback will call driver's callback
> > > > > > 
> > > > > > I checked pci_walk_bus users one by one, and found only PCIe aer needs
> > > > > > device lock.
> > > > > [...]
> > > > > 
> > > > > What about eeh_report_error() in
> > > > > arch/powerpc/platforms/pseries/eeh_driver.c?
> > > > 
> > > > En...  Because pci_walk_bus() invocation is removed in 3.7, so this
> > > > patch is only valid for 3.7.  We need another version for 3.6.
> > > 
> > > Here is the patch for 3.6.  I have no powerpc machine, so build test
> > > only.
> > > 
> > > Subject: [BUGFIX] PCI/PM: Fix deadlock when unbind device if its parent in D3cold
> > > 
> > > If a PCI device and its parents are put into D3cold, unbinding the
> > > device will trigger deadlock as follow:
> > > 
> > > - driver_unbind
> > >   - device_release_driver
> > >     - device_lock(dev)				<--- previous lock here
> > >     - __device_release_driver
> > >       - pm_runtime_get_sync
> > >         ...
> > >           - rpm_resume(dev)
> > >             - rpm_resume(dev->parent)
> > >               ...
> > >                 - pci_pm_runtime_resume
> > >                   ...
> > >                   - pci_set_power_state
> > >                     - __pci_start_power_transition
> > >                       - pci_wakeup_bus(dev->parent->subordinate)
> > >                         - pci_walk_bus
> > >                           - device_lock(dev)	<--- dead lock here
> > > 
> > > 
> > > If we do not do device_lock in pci_walk_bus, we can avoid dead lock.
> > > Device_lock in pci_walk_bus is introduced in commit:
> > > d71374dafbba7ec3f67371d3b7e9f6310a588808, corresponding email thread
> > > is: https://lkml.org/lkml/2006/5/26/38.  The patch author Zhang Yanmin
> > > said device_lock is added to pci_walk_bus because:
> > > 
> > >   Some error handling functions call pci_walk_bus. For example, PCIe
> > >   aer. Here we lock the device, so the driver wouldn't detach from the
> > >   device, as the cb might call driver's callback function.
> > > 
> > > So I fixed the dead lock as follow:
> > > 
> > > - remove device_lock from pci_walk_bus
> > > - add device_lock into callback if callback will call driver's callback
> > > 
> > > I checked pci_walk_bus users one by one, and found only PCIe aer needs
> > > device lock.
> > > 
> > > Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx>
> > > Cc: Zhang Yanmin <yanmin.zhang@xxxxxxxxx>
> > > ---
> > >  arch/powerpc/platforms/pseries/eeh_driver.c |   51 ++++++++++++++++++----------
> > 
> > Due to me applying a power pci patch,
> > feadf7c0a1a7c08c74bebb4a13b755f8c40e3bbc in Linus's tree to 3.6-stable,
> > this patch doesn't apply here anymore.
> > 
> > Because that patch is in the tree, is it now just safe to take your
> > original, unmodified, version of this patch for 3.6-stable?
> 
> No.  My original version does not work.  I need to rebase my patch on
> this patch.  Which tree should I base?

Which tree should I base the patch on?

Best Regards,
Huang Ying


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