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PCI: Fix "try" semantics of bus and slot reset

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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: b014e96d1a ("PCI: Protect pci_error_handlers->reset_notify() usage with device_lock()")
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Sinan Kaya <okaya@kernel.org>
This commit is contained in:
Alex Williamson 2019-02-18 12:46:46 -07:00 committed by Bjorn Helgaas
parent 20a796a969
commit ddefc033ee
1 changed files with 26 additions and 28 deletions
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54
drivers/pci/pci.c
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@ -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;
}