| Message ID | 155051908423.10656.10601490787034368635.stgit@gimli.home (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | [v2] PCI: Fix "try" semantics of bus and slot reset | expand |
On 2/18/2019 2:46 PM, Alex Williamson wrote: > 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: b014e96d1abb ("PCI: Protect pci_error_handlers->reset_notify() usage with device_lock()") > Signed-off-by: Alex Williamson <alex.williamson@redhat.com> > --- Reviewed-by: Sinan Kaya <okaya@kernel.org>
On Mon, Feb 18, 2019 at 12:46:46PM -0700, Alex Williamson wrote: > 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: b014e96d1abb ("PCI: Protect pci_error_handlers->reset_notify() usage with device_lock()") > Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Applied with Sinan's reviewed-by to pci/misc for v5.1, thanks, Alex! > --- > drivers/pci/pci.c | 54 ++++++++++++++++++++++++++--------------------------- > 1 file changed, 26 insertions(+), 28 deletions(-) > > v2: White space only fix suggested by Myron Stowe, removing an additional > empty line from __pci_reset_slot() after the restore call is moved. > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index c25acace7d91..2fb149216cde 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -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; > } > >
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index c25acace7d91..2fb149216cde 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -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; }
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: b014e96d1abb ("PCI: Protect pci_error_handlers->reset_notify() usage with device_lock()") Signed-off-by: Alex Williamson <alex.williamson@redhat.com> --- drivers/pci/pci.c | 54 ++++++++++++++++++++++++++--------------------------- 1 file changed, 26 insertions(+), 28 deletions(-) v2: White space only fix suggested by Myron Stowe, removing an additional empty line from __pci_reset_slot() after the restore call is moved.