From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH v3 2/2] vhost: Add VHOST PMD
Date: Mon, 9 Nov 2015 14:22:05 -0800
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To: Tetsuya Mukawa <mukawa@igel.co.jp>
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On Mon,  9 Nov 2015 14:17:01 +0900
Tetsuya Mukawa <mukawa@igel.co.jp> wrote:

> +	rte_atomic32_set(&r->while_queuing, 1);
> +
> +	if (unlikely(rte_atomic32_read(&r->allow_queuing) == 0))
> +		goto out;

You special 2 variable custom locking here is buggy.
If you hit second atomic test, you will leave while_queuing set.