Re: [BUGFIX 1/2] PCI/PM: Fix deadlock when unbind device if itsparent in D3cold

[Bjorn Helgaas]

On Fri, Nov 2, 2012 at 11:06 PM, Huang Ying <ying.huang@xxxxxxxxx> wrote:
> On Fri, 2012-11-02 at 10:50 -0600, Bjorn Helgaas wrote:
>> On Wed, Oct 24, 2012 at 12:54 AM, Huang Ying <ying.huang@xxxxxxxxx> wrote:
>> > 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.
>>
>> Is there a problem report or bugzilla for this issue?
>
> No.  I found this issue when I developed kexec fixing.
>
> Best Regards,
> Huang Ying
>
>> > Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx>
>> > Cc: Zhang Yanmin <yanmin.zhang@xxxxxxxxx>
>>
>> Should this go to stable as well?  The D3cold support appeared in
>> v3.6, so my guess is that this fix could go to v3.6.x.

What about the stable tree?

>> > ---
>> >  drivers/pci/bus.c                  |    3 ---
>> >  drivers/pci/pcie/aer/aerdrv_core.c |   20 ++++++++++++++++----
>> >  2 files changed, 16 insertions(+), 7 deletions(-)
>> >
>> > --- a/drivers/pci/bus.c
>> > +++ b/drivers/pci/bus.c
>> > @@ -320,10 +320,7 @@ void pci_walk_bus(struct pci_bus *top, i
>> >                 } else
>> >                         next = dev->bus_list.next;
>> >
>> > -               /* Run device routines with the device locked */
>> > -               device_lock(&dev->dev);
>> >                 retval = cb(dev, userdata);
>> > -               device_unlock(&dev->dev);
>> >                 if (retval)
>> >                         break;
>> >         }
>> > --- a/drivers/pci/pcie/aer/aerdrv_core.c
>> > +++ b/drivers/pci/pcie/aer/aerdrv_core.c
>> > @@ -213,6 +213,7 @@ static int report_error_detected(struct
>> >         struct aer_broadcast_data *result_data;
>> >         result_data = (struct aer_broadcast_data *) data;
>> >
>> > +       device_lock(&dev->dev);
>> >         dev->error_state = result_data->state;
>> >
>> >         if (!dev->driver ||
>> > @@ -231,12 +232,14 @@ static int report_error_detected(struct
>> >                                    dev->driver ?
>> >                                    "no AER-aware driver" : "no driver");
>> >                 }
>> > -               return 0;
>> > +               goto out;
>> >         }
>> >
>> >         err_handler = dev->driver->err_handler;
>> >         vote = err_handler->error_detected(dev, result_data->state);
>> >         result_data->result = merge_result(result_data->result, vote);
>> > +out:
>> > +       device_unlock(&dev->dev);
>> >         return 0;
>> >  }
>> >
>> > @@ -247,14 +250,17 @@ static int report_mmio_enabled(struct pc
>> >         struct aer_broadcast_data *result_data;
>> >         result_data = (struct aer_broadcast_data *) data;
>> >
>> > +       device_lock(&dev->dev);
>> >         if (!dev->driver ||
>> >                 !dev->driver->err_handler ||
>> >                 !dev->driver->err_handler->mmio_enabled)
>> > -               return 0;
>> > +               goto out;
>> >
>> >         err_handler = dev->driver->err_handler;
>> >         vote = err_handler->mmio_enabled(dev);
>> >         result_data->result = merge_result(result_data->result, vote);
>> > +out:
>> > +       device_unlock(&dev->dev);
>> >         return 0;
>> >  }
>> >
>> > @@ -265,14 +271,17 @@ static int report_slot_reset(struct pci_
>> >         struct aer_broadcast_data *result_data;
>> >         result_data = (struct aer_broadcast_data *) data;
>> >
>> > +       device_lock(&dev->dev);
>> >         if (!dev->driver ||
>> >                 !dev->driver->err_handler ||
>> >                 !dev->driver->err_handler->slot_reset)
>> > -               return 0;
>> > +               goto out;
>> >
>> >         err_handler = dev->driver->err_handler;
>> >         vote = err_handler->slot_reset(dev);
>> >         result_data->result = merge_result(result_data->result, vote);
>> > +out:
>> > +       device_unlock(&dev->dev);
>> >         return 0;
>> >  }
>> >
>> > @@ -280,15 +289,18 @@ static int report_resume(struct pci_dev
>> >  {
>> >         const struct pci_error_handlers *err_handler;
>> >
>> > +       device_lock(&dev->dev);
>> >         dev->error_state = pci_channel_io_normal;
>> >
>> >         if (!dev->driver ||
>> >                 !dev->driver->err_handler ||
>> >                 !dev->driver->err_handler->resume)
>> > -               return 0;
>> > +               goto out;
>> >
>> >         err_handler = dev->driver->err_handler;
>> >         err_handler->resume(dev);
>> > +out:
>> > +       device_unlock(&dev->dev);
>> >         return 0;
>> >  }
>> >
>
>
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