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Message-ID: <CAErSpo7hiFQOC+OPZretkyp5EcL84zEWCAiQgEE5Ewq--gUziQ@mail.gmail.com>
Date: Fri, 2 Nov 2012 10:50:50 -0600
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: Huang Ying <ying.huang@...el.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 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.
> ---
> 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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