From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH v4 5/8] net/vdev_netvsc: implement core
	functionality
Date: Thu, 18 Jan 2018 10:25:39 -0800
Message-ID: <20180118102539.02da1cff@xeon-e3>
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Cc: Ferruh Yigit <ferruh.yigit@intel.com>, Thomas Monjalon
 <thomas@monjalon.net>, dev@dpdk.org, Adrien Mazarguil
 <adrien.mazarguil@6wind.com>
To: Matan Azrad <matan@mellanox.com>
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On Thu, 18 Jan 2018 08:43:43 +0000
Matan Azrad <matan@mellanox.com> wrote:

> +
> +/**
> + * Alarm callback that regularly probes system network interfaces.
> + *
> + * This callback runs at a frequency determined by VDEV_NETVSC_PROBE_MS as
> + * long as an vdev_netvsc context instance exists.
> + *
> + * @param arg
> + *   Ignored.
> + */
> +static void
> +vdev_netvsc_alarm(__rte_unused void *arg)
> +{
> +	struct vdev_netvsc_ctx *ctx;
> +	int ret;
> +
> +	LIST_FOREACH(ctx, &vdev_netvsc_ctx_list, entry) {
> +		ret = vdev_netvsc_foreach_iface(vdev_netvsc_device_probe, ctx);
> +		if (ret)
> +			break;
> +	}
> +	if (!vdev_netvsc_ctx_count)
> +		return;
> +	ret = rte_eal_alarm_set(VDEV_NETVSC_PROBE_MS * 1000,
> +				vdev_netvsc_alarm, NULL);
> +	if (ret < 0) {
> +		DRV_LOG(ERR, "unable to reschedule alarm callback: %s",
> +			rte_strerror(-ret));
> +	}
> +}
> +

Not a fan of polling for network interface changes.
Alarms in core code make life difficult for applications.

Also, at least on current Azure infrastructure hotplug of netvsc devices
is not supported.

Can we just wait until proper hotplug API from kernel (ie read netlink uevent)
is done?