Commit ddefc033 authored by Alex Williamson's avatar Alex Williamson Committed by Bjorn Helgaas
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PCI: Fix "try" semantics of bus and slot reset 



The commit referenced below introduced device locking around save and
restore of state for each device during a PCI bus "try" reset, making it
decidely non-"try" and prone to deadlock in the event that a device is
already locked.  Restore __pci_reset_bus() and __pci_reset_slot() to their
advertised locking semantics by pushing the save and restore functions into
the branch where the entire tree is already locked.  Extend the helper
function names with "_locked" and update the comment to reflect this
calling requirement.

Fixes: b014e96d ("PCI: Protect pci_error_handlers->reset_notify() usage with device_lock()")
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarSinan Kaya <okaya@kernel.org>
parent 20a796a9

drivers/pci/pci.c

+26 −28
Original line number Diff line number Diff line
@@ -5058,39 +5058,42 @@ static int pci_slot_trylock(struct pci_slot *slot) 
	return 0;

}



/* Save and disable devices from the top of the tree down */

static void pci_bus_save_and_disable(struct pci_bus *bus)

/*

 * Save and disable devices from the top of the tree down while holding

 * the @dev mutex lock for the entire tree.

 */

static void pci_bus_save_and_disable_locked(struct pci_bus *bus)

{

	struct pci_dev *dev;



	list_for_each_entry(dev, &bus->devices, bus_list) {

		pci_dev_lock(dev);

		pci_dev_save_and_disable(dev);

		pci_dev_unlock(dev);

		if (dev->subordinate)

			pci_bus_save_and_disable(dev->subordinate);

			pci_bus_save_and_disable_locked(dev->subordinate);

	}

}



/*

 * Restore devices from top of the tree down - parent bridges need to be

 * restored before we can get to subordinate devices.

 * Restore devices from top of the tree down while holding @dev mutex lock

 * for the entire tree.  Parent bridges need to be restored before we can

 * get to subordinate devices.

 */

static void pci_bus_restore(struct pci_bus *bus)

static void pci_bus_restore_locked(struct pci_bus *bus)

{

	struct pci_dev *dev;



	list_for_each_entry(dev, &bus->devices, bus_list) {

		pci_dev_lock(dev);

		pci_dev_restore(dev);

		pci_dev_unlock(dev);

		if (dev->subordinate)

			pci_bus_restore(dev->subordinate);

			pci_bus_restore_locked(dev->subordinate);

	}

}



/* Save and disable devices from the top of the tree down */

static void pci_slot_save_and_disable(struct pci_slot *slot)

/*

 * Save and disable devices from the top of the tree down while holding

 * the @dev mutex lock for the entire tree.

 */

static void pci_slot_save_and_disable_locked(struct pci_slot *slot)

{

	struct pci_dev *dev;
@@ -5099,26 +5102,25 @@ static void pci_slot_save_and_disable(struct pci_slot *slot) 
			continue;

		pci_dev_save_and_disable(dev);

		if (dev->subordinate)

			pci_bus_save_and_disable(dev->subordinate);

			pci_bus_save_and_disable_locked(dev->subordinate);

	}

}



/*

 * Restore devices from top of the tree down - parent bridges need to be

 * restored before we can get to subordinate devices.

 * Restore devices from top of the tree down while holding @dev mutex lock

 * for the entire tree.  Parent bridges need to be restored before we can

 * get to subordinate devices.

 */

static void pci_slot_restore(struct pci_slot *slot)

static void pci_slot_restore_locked(struct pci_slot *slot)

{

	struct pci_dev *dev;



	list_for_each_entry(dev, &slot->bus->devices, bus_list) {

		if (!dev->slot || dev->slot != slot)

			continue;

		pci_dev_lock(dev);

		pci_dev_restore(dev);

		pci_dev_unlock(dev);

		if (dev->subordinate)

			pci_bus_restore(dev->subordinate);

			pci_bus_restore_locked(dev->subordinate);

	}

}
@@ -5177,17 +5179,15 @@ static int __pci_reset_slot(struct pci_slot *slot) 
	if (rc)

		return rc;



	pci_slot_save_and_disable(slot);



	if (pci_slot_trylock(slot)) {

		pci_slot_save_and_disable_locked(slot);

		might_sleep();

		rc = pci_reset_hotplug_slot(slot->hotplug, 0);

		pci_slot_restore_locked(slot);

		pci_slot_unlock(slot);

	} else

		rc = -EAGAIN;



	pci_slot_restore(slot);



	return rc;

}
@@ -5273,17 +5273,15 @@ static int __pci_reset_bus(struct pci_bus *bus) 
	if (rc)

		return rc;



	pci_bus_save_and_disable(bus);



	if (pci_bus_trylock(bus)) {

		pci_bus_save_and_disable_locked(bus);

		might_sleep();

		rc = pci_bridge_secondary_bus_reset(bus->self);

		pci_bus_restore_locked(bus);

		pci_bus_unlock(bus);

	} else

		rc = -EAGAIN;



	pci_bus_restore(bus);



	return rc;

}