Re: [dpdk-dev] [PATCH v2] igb_uio: allow multi-process access

[Tiwei Bie <tiwei.bie@intel.com>]

Hi,

On Tue, Dec 19, 2017 at 07:42:20AM -0800, Xiao Wang wrote:
> @@ -336,6 +337,10 @@ struct rte_uio_pci_dev {
>  	struct pci_dev *dev = udev->pdev;
>  	int err;
>  
> +	atomic_inc(&udev->refcnt);
> +	if (atomic_read(&udev->refcnt) > 1)

The "inc and read" should be atomic. Otherwise below
sequence may happen:

P1: atomic_inc(&udev->refcnt);
P2: atomic_inc(&udev->refcnt);
P1: if (atomic_read(&udev->refcnt) > 1)
P2: if (atomic_read(&udev->refcnt) > 1)

> +		return 0;
> +
>  	/* set bus master, which was cleared by the reset function */
>  	pci_set_master(dev);
>  
> @@ -354,6 +359,10 @@ struct rte_uio_pci_dev {
>  	struct rte_uio_pci_dev *udev = info->priv;
>  	struct pci_dev *dev = udev->pdev;
>  
> +	atomic_dec(&udev->refcnt);
> +	if (atomic_read(&udev->refcnt) > 0)
> +		return 0;

Ditto.

Best regards,
Tiwei Bie

> +
>  	/* disable interrupts */
>  	igbuio_pci_disable_interrupts(udev);
>  
> -- 
> 1.8.3.1
>