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Message-ID: <155051908423.10656.10601490787034368635.stgit@gimli.home>
Date: Mon, 18 Feb 2019 12:46:46 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: linux-pci@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, bhelgaas@...gle.com, hch@....de,
okaya@...nel.org, myron.stowe@...hat.com
Subject: [PATCH v2] 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: b014e96d1abb ("PCI: Protect pci_error_handlers->reset_notify() usage with device_lock()")
Signed-off-by: Alex Williamson <alex.williamson@...hat.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.
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;
}
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