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Commit 90b5c1d7 authored by Huang Ying's avatar Huang Ying Committed by Bjorn Helgaas
Browse files

PCI/PM: Fix deadlock when unbinding device if 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)	<--- 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:
d71374da, 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.

Signed-off-by: default avatarHuang Ying <ying.huang@intel.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Acked-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
CC: stable@vger.kernel.org		# v3.6+
CC: Zhang Yanmin <yanmin.zhang@intel.com>
parent 8f0d8163

drivers/pci/bus.c

+0 −3
Original line number Diff line number Diff line
@@ -320,10 +320,7 @@ void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), 
		} 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;

	}

drivers/pci/pcie/aer/aerdrv_core.c

+16 −4
Original line number Diff line number Diff line
@@ -213,6 +213,7 @@ static int report_error_detected(struct pci_dev *dev, void *data) 
	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 pci_dev *dev, void *data) 
				   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 pci_dev *dev, void *data) 
	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_dev *dev, void *data) 
	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 *dev, void *data) 
{

	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;

}