Re: [PATCH 2/2] pci: fix slot reset device locking

[<dan.j.williams@intel.com>]

Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> Like pci_bus_lock, pci_slot_lock needs to lock the bridge device to
> prevent the warning:
> 
>   pcieport 0000:e2:05.0: unlocked secondary bus reset via: pciehp_reset_slot+0x55/0xa0
> 
> Signed-off-by: Keith Busch <kbusch@kernel.org>
> ---
>  drivers/pci/pci.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 3378221c5723a..5f8b0d06a1459 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5460,6 +5460,8 @@ static void pci_slot_lock(struct pci_slot *slot)
>  {
>  	struct pci_dev *dev;
>  
> +	if (slot->bus->self)
> +		pci_dev_lock(slot->bus->self);
>  	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
>  		if (!dev->slot || dev->slot != slot)
>  			continue;
> @@ -5483,12 +5485,17 @@ static void pci_slot_unlock(struct pci_slot *slot)
>  		else
>  			pci_dev_unlock(dev);
>  	}
> +	if (slot->bus->self)
> +		pci_dev_unlock(slot->bus->self);

Given how much context is needed to understand that this looks right, I
would not say no to a follow-on patch that adds kdoc for these locking
functions.

At a minimum I think a breadcrumb of a local "bridge = slot->bus->self"
variable would help.

>  }
>  
>  /* Return 1 on successful lock, 0 on contention */
>  static int pci_slot_trylock(struct pci_slot *slot)
>  {
> -	struct pci_dev *dev;
> +	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)
> @@ -5511,6 +5518,9 @@ static int pci_slot_trylock(struct pci_slot *slot)
>  		else
>  			pci_dev_unlock(dev);
>  	}
> +
> +	if (bridge)
> +		pci_dev_unlock(bridge);
>  	return 0;

Even without the above cosmetic fixup, looks good.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>