[dpdk-dev] [PATCH v8 04/19] ethdev: introduce device lock

[Yuanhan Liu]

On Mon, Jul 2, 2018, at 1:44 PM, Qi Zhang wrote:
> Introduce API rte_eth_dev_lock and rte_eth_dev_unlock to let
> application lock or unlock on specific ethdev, a locked device
> can't be detached, this help applicaiton to prevent unexpected
> device detaching, especially in multi-process envrionment.

I'm just wondering why the need of introducing such 2 (very specific)
APIs, judging that it  looks like a ref count could solve this kind of issues
perfectly.

Also, the API name (_dev_lock/unlock) looks like an over killing, judging
that you just want to pin a device (if I understand this commit log correctly).
What firstly comes to my mind when I see "lock" was "no one can *access*
a device after another has grabbed the lock", which doesn't quite match
what you described here.

That said, if I were you, I would go with introducing few generic refcount
APIs.

        --yliu


> 
> Aslo introduce the new API rte_eth_dev_lock_with_callback and
> rte_eth_dev_unlock_with callback to let application to register
> a callback function which will be invoked before a device is going
> to be detached, the return value of the function will decide if
> device will continue be detached or not, this support application
> to do condition check at runtime.
> 
> Signed-off-by: Qi Zhang <qi.z.zhang at intel.com>
> Reviewed-by: Anatoly Burakov <anatoly.burakov at intel.com>