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Date: Sun, 04 Nov 2012 11:38:45 +0800
From: Huang Ying <ying.huang@...el.com>
To: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
Zhang Yanmin <yanmin.zhang@...el.com>
Subject: Re: [BUGFIX 1/2] PCI/PM: Fix deadlock when unbind device if its
parent in D3cold
On Sat, 2012-11-03 at 11:22 -0600, Bjorn Helgaas wrote:
> On Fri, Nov 2, 2012 at 11:06 PM, Huang Ying <ying.huang@...el.com> 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@...el.com> 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@...el.com>
> >> > Cc: Zhang Yanmin <yanmin.zhang@...el.com>
> >>
> >> 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?
You are right. This fix should go to v3.6.x stable tree.
Best Regards,
Huang Ying
> >> > ---
> >> > 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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