Re: [PATCH v2 1/1] PCI: Consolidate pci_bus/slot_lock/unlock/trylock()

[Bjorn Helgaas]

On Wed, Mar 04, 2026 at 02:21:38PM +0200, Ilpo Järvinen wrote:
> pci_bus/slot_lock/unlock/trylock() largely duplicate the bus iteration
> loop with variation only due to slot filter handling. The only
> differences in the loops is where the struct bus is found (directly in
> the argument vs in slot->bus) and whether slot filter is applied. Those
> difference are simple to handle using function parameters.
> 
> Consolidate the bus iteration loop to one place by creating
> __pci_bus_{lock,unlock,trylock}() and call them from the non-underscore
> locking functions.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>

Applied to pci/reset for v7.1, thanks, Ilpo.

> ---
> 
> v2:
> - Rebased
> - Fixed rollback path dereferencing slot->bus (changed to use the bus
>   parameter directly as slot can be NULL)
> 
>  drivers/pci/pci.c | 115 ++++++++++++++++++++--------------------------
>  1 file changed, 49 insertions(+), 66 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 8479c2e1f74f..c248224e0861 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5292,13 +5292,21 @@ static bool pci_bus_resettable(struct pci_bus *bus)
>  	return true;
>  }
>  
> +static void pci_bus_lock(struct pci_bus *bus);
> +static void pci_bus_unlock(struct pci_bus *bus);
> +static int pci_bus_trylock(struct pci_bus *bus);
> +
>  /* Lock devices from the top of the tree down */
> -static void pci_bus_lock(struct pci_bus *bus)
> +static void __pci_bus_lock(struct pci_bus *bus, struct pci_slot *slot)
>  {
> -	struct pci_dev *dev;
> +	struct pci_dev *dev, *bridge = bus->self;
> +
> +	if (bridge)
> +		pci_dev_lock(bridge);
>  
> -	pci_dev_lock(bus->self);
>  	list_for_each_entry(dev, &bus->devices, bus_list) {
> +		if (slot && (!dev->slot || dev->slot != slot))
> +			continue;
>  		if (dev->subordinate)
>  			pci_bus_lock(dev->subordinate);
>  		else
> @@ -5307,28 +5315,34 @@ static void pci_bus_lock(struct pci_bus *bus)
>  }
>  
>  /* Unlock devices from the bottom of the tree up */
> -static void pci_bus_unlock(struct pci_bus *bus)
> +static void __pci_bus_unlock(struct pci_bus *bus, struct pci_slot *slot)
>  {
> -	struct pci_dev *dev;
> +	struct pci_dev *dev, *bridge = bus->self;
>  
>  	list_for_each_entry(dev, &bus->devices, bus_list) {
> +		if (slot && (!dev->slot || dev->slot != slot))
> +			continue;
>  		if (dev->subordinate)
>  			pci_bus_unlock(dev->subordinate);
>  		else
>  			pci_dev_unlock(dev);
>  	}
> -	pci_dev_unlock(bus->self);
> +
> +	if (bridge)
> +		pci_dev_unlock(bridge);
>  }
>  
>  /* Return 1 on successful lock, 0 on contention */
> -static int pci_bus_trylock(struct pci_bus *bus)
> +static int __pci_bus_trylock(struct pci_bus *bus, struct pci_slot *slot)
>  {
> -	struct pci_dev *dev;
> +	struct pci_dev *dev, *bridge = bus->self;
>  
> -	if (!pci_dev_trylock(bus->self))
> +	if (bridge && !pci_dev_trylock(bridge))
>  		return 0;
>  
>  	list_for_each_entry(dev, &bus->devices, bus_list) {
> +		if (slot && (!dev->slot || dev->slot != slot))
> +			continue;
>  		if (dev->subordinate) {
>  			if (!pci_bus_trylock(dev->subordinate))
>  				goto unlock;
> @@ -5339,15 +5353,37 @@ static int pci_bus_trylock(struct pci_bus *bus)
>  
>  unlock:
>  	list_for_each_entry_continue_reverse(dev, &bus->devices, bus_list) {
> +		if (slot && (!dev->slot || dev->slot != slot))
> +			continue;
>  		if (dev->subordinate)
>  			pci_bus_unlock(dev->subordinate);
>  		else
>  			pci_dev_unlock(dev);
>  	}
> -	pci_dev_unlock(bus->self);
> +
> +	if (bridge)
> +		pci_dev_unlock(bridge);
>  	return 0;
>  }
>  
> +/* Lock devices from the top of the tree down */
> +static void pci_bus_lock(struct pci_bus *bus)
> +{
> +	__pci_bus_lock(bus, NULL);
> +}
> +
> +/* Unlock devices from the bottom of the tree up */
> +static void pci_bus_unlock(struct pci_bus *bus)
> +{
> +	__pci_bus_unlock(bus, NULL);
> +}
> +
> +/* Return 1 on successful lock, 0 on contention */
> +static int pci_bus_trylock(struct pci_bus *bus)
> +{
> +	return __pci_bus_trylock(bus, NULL);
> +}
> +
>  /* Do any devices on or below this slot prevent a bus reset? */
>  static bool pci_slot_resettable(struct pci_slot *slot)
>  {
> @@ -5370,72 +5406,19 @@ static bool pci_slot_resettable(struct pci_slot *slot)
>  /* Lock devices from the top of the tree down */
>  static void pci_slot_lock(struct pci_slot *slot)
>  {
> -	struct pci_dev *dev, *bridge = slot->bus->self;
> -
> -	if (bridge)
> -		pci_dev_lock(bridge);
> -
> -	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
> -		if (!dev->slot || dev->slot != slot)
> -			continue;
> -		if (dev->subordinate)
> -			pci_bus_lock(dev->subordinate);
> -		else
> -			pci_dev_lock(dev);
> -	}
> +	__pci_bus_lock(slot->bus, slot);
>  }
>  
>  /* Unlock devices from the bottom of the tree up */
>  static void pci_slot_unlock(struct pci_slot *slot)
>  {
> -	struct pci_dev *dev, *bridge = slot->bus->self;
> -
> -	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
> -		if (!dev->slot || dev->slot != slot)
> -			continue;
> -		if (dev->subordinate)
> -			pci_bus_unlock(dev->subordinate);
> -		else
> -			pci_dev_unlock(dev);
> -	}
> -
> -	if (bridge)
> -		pci_dev_unlock(bridge);
> +	__pci_bus_unlock(slot->bus, slot);
>  }
>  
>  /* Return 1 on successful lock, 0 on contention */
>  static int pci_slot_trylock(struct pci_slot *slot)
>  {
> -	struct pci_dev *dev, *bridge = slot->bus->self;
> -
> -	if (bridge && !pci_dev_trylock(bridge))
> -		return 0;
> -
> -	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
> -		if (!dev->slot || dev->slot != slot)
> -			continue;
> -		if (dev->subordinate) {
> -			if (!pci_bus_trylock(dev->subordinate))
> -				goto unlock;
> -		} else if (!pci_dev_trylock(dev))
> -			goto unlock;
> -	}
> -	return 1;
> -
> -unlock:
> -	list_for_each_entry_continue_reverse(dev,
> -					     &slot->bus->devices, bus_list) {
> -		if (!dev->slot || dev->slot != slot)
> -			continue;
> -		if (dev->subordinate)
> -			pci_bus_unlock(dev->subordinate);
> -		else
> -			pci_dev_unlock(dev);
> -	}
> -
> -	if (bridge)
> -		pci_dev_unlock(bridge);
> -	return 0;
> +	return __pci_bus_trylock(slot->bus, slot);
>  }
>  
>  /*
> 
> base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
> -- 
> 2.39.5
>