Re: [dpdk-dev] [PATCH 3/3] app/testpmd: fix callback issue for hot-unplug

[Matan Azrad <matan@mellanox.com>]

Hi Jeff

 From: Jeff Guo <jia.guo@intel.com>
> Before detach device when device be hot-unplugged, the failure process in
> user space and kernel space both need to be finished, such as eal interrupt
> callback need to be inactive before the callback be unregistered when device
> is being cleaned. This patch add rte alarm for device detaching, with that it
> could finish interrupt callback soon and give time to let the failure process
> done before detaching.
> 
> Fixes: 2049c5113fe8 ("app/testpmd: use hotplug failure handler")
> Signed-off-by: Jeff Guo <jia.guo@intel.com>
> ---
>  app/test-pmd/testpmd.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c index
> 9c0edca..9c673cf 100644
> --- a/app/test-pmd/testpmd.c
> +++ b/app/test-pmd/testpmd.c
> @@ -2620,7 +2620,18 @@ eth_dev_event_callback(const char
> *device_name, enum rte_dev_event_type type,
>  				device_name);
>  			return;
>  		}
> -		rmv_event_callback((void *)(intptr_t)port_id);
> +		/*
> +		 * Before detach device, the hot-unplug failure process in
> +		 * user space and kernel space both need to be finished,
> +		 * such as eal interrupt callback need to be inactive before
> +		 * the callback be unregistered when device is being cleaned.
> +		 * So finished interrupt callback soon here and give time to
> +		 * let the work done before detaching.
> +		 */
> +		if (rte_eal_alarm_set(100000,
> +				rmv_event_callback, (void
> *)(intptr_t)port_id))
> +			RTE_LOG(ERR, EAL,
> +				"Could not set up deferred device


It looks me strange to use callback and alarm to remove a device:
Why not to use callback and that is it?

I think that it's better to let the EAL to detach the device after all the callbacks were done and not to do it by the user callback.
So the application\callback owners just need to clean its resources with understanding that after the callback the device(and the callback itself) will be detached by the EAL. 


> removal\n");
>  		break;
>  	case RTE_DEV_EVENT_ADD:
>  		RTE_LOG(ERR, EAL, "The device: %s has been added!\n",
> --
> 2.7.4