From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH v2] igb_uio: allow multi-process access
Date: Tue, 19 Dec 2017 07:39:01 -0800
Message-ID: <20171219073901.6d048a47@xeon-e3>
References: <1512784653-128951-1-git-send-email-xiao.w.wang@intel.com>
 <1513698140-92837-1-git-send-email-xiao.w.wang@intel.com>
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Cc: ferruh.yigit@intel.com, dev@dpdk.org
To: Xiao Wang <xiao.w.wang@intel.com>
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On Tue, 19 Dec 2017 07:42:20 -0800
Xiao Wang <xiao.w.wang@intel.com> wrote:

> +	atomic_dec(&udev->refcnt);
> +	if (atomic_read(&udev->refcnt) > 0)
> +		return 0;
> +

The point of using atomic functions is to do atomic operations.
You need to use atomic_dec_and_test here.