Re: [PATCH] PCI: Fix missing lockdep annotation for pci_cfg_access_trylock()

[Dave Jiang <dave.jiang@intel.com>]

On 5/24/24 6:19 PM, Dan Williams wrote:
> Alex reports a new vfio-pci lockdep warning resulting from the
> cfg_access_lock lock_map added recently.
> 
> Add the missing annotation to pci_cfg_access_trylock() and adjust the
> lock_map acquisition to be symmetrical relative to pci_lock.
> 
> Fixes: 7e89efc6e9e4 ("PCI: Lock upstream bridge for pci_reset_function()")
> Reported-by: Alex Williamson <alex.williamson@redhat.com>
> Closes: http://lore.kernel.org/r/20240523131005.5578e3de.alex.williamson@redhat.com
> Tested-by: Alex Williamson <alex.williamson@redhat.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
>  drivers/pci/access.c |   10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
> index 30f031de9cfe..3595130ff719 100644
> --- a/drivers/pci/access.c
> +++ b/drivers/pci/access.c
> @@ -289,11 +289,10 @@ void pci_cfg_access_lock(struct pci_dev *dev)
>  {
>  	might_sleep();
>  
> -	lock_map_acquire(&dev->cfg_access_lock);
> -
>  	raw_spin_lock_irq(&pci_lock);
>  	if (dev->block_cfg_access)
>  		pci_wait_cfg(dev);
> +	lock_map_acquire(&dev->cfg_access_lock);
>  	dev->block_cfg_access = 1;
>  	raw_spin_unlock_irq(&pci_lock);
>  }
> @@ -315,8 +314,10 @@ bool pci_cfg_access_trylock(struct pci_dev *dev)
>  	raw_spin_lock_irqsave(&pci_lock, flags);
>  	if (dev->block_cfg_access)
>  		locked = false;
> -	else
> +	else {
> +		lock_map_acquire(&dev->cfg_access_lock);
>  		dev->block_cfg_access = 1;
> +	}
>  	raw_spin_unlock_irqrestore(&pci_lock, flags);
>  
>  	return locked;
> @@ -342,11 +343,10 @@ void pci_cfg_access_unlock(struct pci_dev *dev)
>  	WARN_ON(!dev->block_cfg_access);
>  
>  	dev->block_cfg_access = 0;
> +	lock_map_release(&dev->cfg_access_lock);
>  	raw_spin_unlock_irqrestore(&pci_lock, flags);
>  
>  	wake_up_all(&pci_cfg_wait);
> -
> -	lock_map_release(&dev->cfg_access_lock);
>  }
>  EXPORT_SYMBOL_GPL(pci_cfg_access_unlock);
>  
>