[PATCH] PCI: Add missing bridge lock in pci_slot_lock()

[PATCH] PCI: Add missing bridge lock in pci_slot_lock()

[Moshe Shemesh]

Unlike pci_bus_lock(), which acquires the lock on the bus bridge before
locking devices and subordinate buses, pci_slot_lock() currently miss
locking the bridge. This may result in triggering warning on
pci_bridge_secondary_bus_reset() [1].

Fix it by adding bridge lock on pci_slot_lock() and pci_slot_trylock().

[1]
pcieport 0000:c1:05.0: unlocked secondary bus reset via: pciehp_reset_slot+0xa4/0x150

Fixes: a4e772898f8b ("PCI: Add missing bridge lock to pci_bus_lock()")
Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
---
 drivers/pci/pci.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e77d5b53c0ce..c31929482122 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5518,6 +5518,7 @@ static void pci_slot_lock(struct pci_slot *slot)
 {
 	struct pci_dev *dev;
 
+	pci_dev_lock(slot->bus->self);
 	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
 		if (!dev->slot || dev->slot != slot)
 			continue;
@@ -5540,6 +5541,7 @@ static void pci_slot_unlock(struct pci_slot *slot)
 			pci_bus_unlock(dev->subordinate);
 		pci_dev_unlock(dev);
 	}
+	pci_dev_unlock(slot->bus->self);
 }
 
 /* Return 1 on successful lock, 0 on contention */
@@ -5547,6 +5549,9 @@ static int pci_slot_trylock(struct pci_slot *slot)
 {
 	struct pci_dev *dev;
 
+	if (!pci_dev_trylock(slot->bus->self))
+		return 0;
+
 	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
 		if (!dev->slot || dev->slot != slot)
 			continue;
@@ -5570,6 +5575,7 @@ static int pci_slot_trylock(struct pci_slot *slot)
 		else
 			pci_dev_unlock(dev);
 	}
+	pci_dev_unlock(slot->bus->self);
 	return 0;
 }
 
-- 
2.34.1

Re: [PATCH] PCI: Add missing bridge lock in pci_slot_lock()

[Moshe Shemesh]

On 5/29/2025 5:59 PM, Moshe Shemesh wrote:
> Unlike pci_bus_lock(), which acquires the lock on the bus bridge before
> locking devices and subordinate buses, pci_slot_lock() currently miss
> locking the bridge. This may result in triggering warning on
> pci_bridge_secondary_bus_reset() [1].

Hi all,
Kind reminder regarding this patch. I'd appreciate any feedback or 
comments.
> 
> Fix it by adding bridge lock on pci_slot_lock() and pci_slot_trylock().
> 
> [1]
> pcieport 0000:c1:05.0: unlocked secondary bus reset via: pciehp_reset_slot+0xa4/0x150
> 
> Fixes: a4e772898f8b ("PCI: Add missing bridge lock to pci_bus_lock()")
> Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
> ---
>   drivers/pci/pci.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index e77d5b53c0ce..c31929482122 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5518,6 +5518,7 @@ static void pci_slot_lock(struct pci_slot *slot)
>   {
>   	struct pci_dev *dev;
>   
> +	pci_dev_lock(slot->bus->self);
>   	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
>   		if (!dev->slot || dev->slot != slot)
>   			continue;
> @@ -5540,6 +5541,7 @@ static void pci_slot_unlock(struct pci_slot *slot)
>   			pci_bus_unlock(dev->subordinate);
>   		pci_dev_unlock(dev);
>   	}
> +	pci_dev_unlock(slot->bus->self);
>   }
>   
>   /* Return 1 on successful lock, 0 on contention */
> @@ -5547,6 +5549,9 @@ static int pci_slot_trylock(struct pci_slot *slot)
>   {
>   	struct pci_dev *dev;
>   
> +	if (!pci_dev_trylock(slot->bus->self))
> +		return 0;
> +
>   	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
>   		if (!dev->slot || dev->slot != slot)
>   			continue;
> @@ -5570,6 +5575,7 @@ static int pci_slot_trylock(struct pci_slot *slot)
>   		else
>   			pci_dev_unlock(dev);
>   	}
> +	pci_dev_unlock(slot->bus->self);
>   	return 0;
>   }
>