[PATCH 1/1] PCI: Fix lock symmetry in pci_slot_unlock()

[PATCH 1/1] PCI: Fix lock symmetry in pci_slot_unlock()

[Ilpo Järvinen]

The commit a4e772898f8b ("PCI: Add missing bridge lock to
pci_bus_lock()") made the lock function to call depend on
dev->subordinate but left pci_slot_unlock() unmodified creating locking
asymmetry compared with pci_slot_lock().

Move pci_dev_unlock() inside an else branch to match the logic in
pci_slot_lock().

Fixes: a4e772898f8b ("PCI: Add missing bridge lock to pci_bus_lock()")
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/pci/pci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4d7c9f64ea24..26507aa906d7 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5542,7 +5542,8 @@ static void pci_slot_unlock(struct pci_slot *slot)
 			continue;
 		if (dev->subordinate)
 			pci_bus_unlock(dev->subordinate);
-		pci_dev_unlock(dev);
+		else
+			pci_dev_unlock(dev);
 	}
 }
 

base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
-- 
2.39.5

Re: [PATCH 1/1] PCI: Fix lock symmetry in pci_slot_unlock()

[Lukas Wunner]

On Wed, Apr 30, 2025 at 11:35:26AM +0300, Ilpo Järvinen wrote:
> The commit a4e772898f8b ("PCI: Add missing bridge lock to
> pci_bus_lock()") made the lock function to call depend on
> dev->subordinate but left pci_slot_unlock() unmodified creating locking
> asymmetry compared with pci_slot_lock().

Worth noting that this isn't just for symmetry:  It seems the bridge
is unlocked twice because pci_bus_unlock() unlocks bus->self and
pci_slot_unlock() then unconditionally unlocks the same bridge device
again.

Thanks,

Lukas