Re: [dpdk-dev] [PATCH 07/11] ethdev: add lock to port allocation check

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed,  9 May 2018 11:43:33 +0200
Thomas Monjalon <thomas@monjalon.net> wrote:

>  
> +struct rte_eth_dev *
> +rte_eth_dev_allocated(const char *name)
> +{
> +	struct rte_eth_dev *ethdev;
> +
> +	rte_eth_dev_shared_data_prepare();
> +
> +	rte_spinlock_lock(&rte_eth_dev_shared_data->ownership_lock);
> +
> +	ethdev = rte_eth_dev_allocated_lock_free(name);
> +
> +	rte_spinlock_unlock(&rte_eth_dev_shared_data->ownership_lock);
> +
> +	return ethdev;
> +}
> +

Not sure about this. The code it self is correct, but it creates
a racy semantic.

If caller doesn't already hold a lock then there is no guarantee that
the device returned won't be destroyed by some other thread or that
the name was just allocated by some other process.