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Message-ID: <3239885.3gHJyAyRVG@vostro.rjw.lan>
Date: Fri, 02 Nov 2012 21:27:08 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Huang Ying <ying.huang@...el.com>, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
Zhang Yanmin <yanmin.zhang@...el.com>
Subject: Re: [BUGFIX 1/2] PCI/PM: Fix deadlock when unbind device if its parent in D3cold
On Friday, November 02, 2012 10:50:50 AM 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?
>
> > 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.
That's correct.
Thanks,
Rafael
> > ---
> > 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;
> > }
> >
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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