From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH V14 1/3] eal: add uevent monitor api and
	callback func
Date: Tue, 30 Jan 2018 16:44:36 -0800
Message-ID: <20180130164436.5d8babcf@xeon-e3>
References: <1516938577-27662-3-git-send-email-jia.guo@intel.com>
 <1517314860-8097-1-git-send-email-jia.guo@intel.com>
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Cc: bruce.richardson@intel.com, gaetan.rivet@6wind.com,
 jingjing.wu@intel.com, thomas@monjalon.net, motih@mellanox.com,
 ferruh.yigit@intel.com, konstantin.ananyev@intel.com,
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 helin.zhang@intel.com, harry.van.haaren@intel.com, jianfeng.tan@intel.com
To: Jeff Guo <jia.guo@intel.com>
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On Tue, 30 Jan 2018 20:20:58 +0800
Jeff Guo <jia.guo@intel.com> wrote:

> +	memset(&ep_kernel, 0, sizeof(struct epoll_event));
> +	ep_kernel.events = EPOLLIN | EPOLLPRI | EPOLLRDHUP | EPOLLHUP;
> +	ep_kernel.data.fd = netlink_fd;
> +	if (epoll_ctl(fd_ep, EPOLL_CTL_ADD, netlink_fd,
> +		&ep_kernel) < 0) {
> +		RTE_LOG(ERR, EAL, "error addding fd to epoll: %m\n");
> +		goto out;
> +	}
> +
> +	while (!service_exit) {
> +		int fdcount;
> +		struct epoll_event ev[1];
> +
> +		fdcount = epoll_wait(fd_ep, ev, 1, -1);
> +		if (fdcount < 0) {
> +			if (errno != EINTR)
> +				RTE_LOG(ERR, EAL, "error receiving uevent "
> +					"message: %m\n");
> +				continue;
> +			}
> +
> +		/* epoll_wait has at least one fd ready to read */
> +		if (dev_uev_process(ev, fdcount) < 0) {
> +			if (errno != EINTR)
> +				RTE_LOG(ERR, EAL, "error processing uevent "
> +					"message: %m\n");
> +		}
> +	}

What is the point of the extra epoll here?
Why not just make netlink_fd blocking and do recv?
Rather than having two syscalls per event.