[Very RFC 40/46] powernv/npu: Don't drop refcount when looking up GPU pci_devs

[Alexey Kardashevskiy]

On 20/11/2019 12:28, Oliver O'Halloran wrote:
> The comment here implies that we don't need to take a ref to the pci_dev
> because the ioda_pe will always have one. This implies that the current
> expection is that the pci_dev for an NPU device will *never* be torn
> down since the ioda_pe having a ref to the device will prevent the
> release function from being called.
> 
> In other words, the desired behaviour here appears to be leaking a ref.
> 
> Nice!


There is a history: https://patchwork.ozlabs.org/patch/1088078/

We did not fix anything in particular then, we do not seem to be fixing
anything now (in other words - we cannot test it in a normal natural
way). I'd drop this one.



> 
> Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
> ---
>  arch/powerpc/platforms/powernv/npu-dma.c | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
> index 72d3749da02c..2eb6e6d45a98 100644
> --- a/arch/powerpc/platforms/powernv/npu-dma.c
> +++ b/arch/powerpc/platforms/powernv/npu-dma.c
> @@ -28,15 +28,10 @@ static struct pci_dev *get_pci_dev(struct device_node *dn)
>  			break;
>  
>  	/*
> -	 * pci_get_domain_bus_and_slot() increased the reference count of
> -	 * the PCI device, but callers don't need that actually as the PE
> -	 * already holds a reference to the device. Since callers aren't
> -	 * aware of the reference count change, call pci_dev_put() now to
> -	 * avoid leaks.
> +	 * NB: for_each_pci_dev() elevates the pci_dev refcount.
> +	 * Caller is responsible for dropping the ref when it's
> +	 * finished with it.
>  	 */
> -	if (pdev)
> -		pci_dev_put(pdev);
> -
>  	return pdev;
>  }
>  
> 

-- 
Alexey