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PCI: Fix pci_slot_trylock() error handling

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Commit a4e772898f ("PCI: Add missing bridge lock to pci_bus_lock()")
delegates the bridge device's pci_dev_trylock() to pci_bus_trylock() in
pci_slot_trylock(), but it forgets to remove the corresponding
pci_dev_unlock() when pci_bus_trylock() fails.

Before a4e772898f, the code did:

  if (!pci_dev_trylock(dev)) /* <- lock bridge device */
    goto unlock;
  if (dev->subordinate) {
    if (!pci_bus_trylock(dev->subordinate)) {
      pci_dev_unlock(dev);   /* <- unlock bridge device */
      goto unlock;
    }
  }

After a4e772898f the bridge-device lock is no longer taken, but the
pci_dev_unlock(dev) on the failure path was left in place, leading to the
bug.

This yields one of two errors:

  1. A warning that the lock is being unlocked when no one holds it.
  2. An incorrect unlock of a lock that belongs to another thread.

Fix it by removing the now-redundant pci_dev_unlock(dev) on the failure
path.

[Same patch later posted by Keith at
https://patch.msgid.link/20260116184150.3013258-1-kbusch@meta.com]

Fixes: a4e772898f ("PCI: Add missing bridge lock to pci_bus_lock()")
Signed-off-by: Jinhui Guo <guojinhui.liam@bytedance.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20251212145528.2555-1-guojinhui.liam@bytedance.com
This commit is contained in:
Jinhui Guo 2025-12-12 22:55:28 +08:00 committed by Bjorn Helgaas
parent c81a2ce6b6
commit 9368d1ee62
1 changed files with 1 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/pci/pci.c
View File

@ -5346,10 +5346,8 @@ static int pci_slot_trylock(struct pci_slot *slot)
if (!dev->slot || dev->slot != slot)
continue;
if (dev->subordinate) {
if (!pci_bus_trylock(dev->subordinate)) {
pci_dev_unlock(dev);
if (!pci_bus_trylock(dev->subordinate))
goto unlock;
}
} else if (!pci_dev_trylock(dev))
goto unlock;
}