linux-kernel - Re: [PATCH 6/7] sock, cgroup: add sock->sk

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Message-ID: <564EFE25.5000906@bmw-carit.de>
Date:	Fri, 20 Nov 2015 12:04:05 +0100
From:	Daniel Wagner <daniel.wagner@...-carit.de>
To:	Tejun Heo <tj@...nel.org>, <davem@...emloft.net>,
	<pablo@...filter.org>, <kaber@...sh.net>,
	<kadlec@...ckhole.kfki.hu>, <lizefan@...wei.com>,
	<hannes@...xchg.org>
CC:	<netdev@...r.kernel.org>, <netfilter-devel@...r.kernel.org>,
	<coreteam@...filter.org>, <cgroups@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <kernel-team@...com>,
	<daniel@...earbox.net>, <nhorman@...driver.com>
Subject: Re: [PATCH 6/7] sock, cgroup: add sock->sk_cgroup

Hi Tejun,

On 11/19/2015 07:52 PM, Tejun Heo wrote:
> +/*
> + * There's a theoretical window where the following accessors race with
> + * updaters and return part of the previous pointer as the prioidx or
> + * classid.  Such races are short-lived and the result isn't critical.
> + */
>  static inline u16 sock_cgroup_prioidx(struct sock_cgroup_data *skcd)
>  {
> -	return skcd->prioidx;
> +	return (skcd->is_data & 1) ? skcd->prioidx : 1;
>  }
>  
>  static inline u32 sock_cgroup_classid(struct sock_cgroup_data *skcd)
>  {
> -	return skcd->classid;
> +	return (skcd->is_data & 1) ? skcd->classid : 0;
>  }


I still try to understand what the code does, hence this stupid question:

Why is sock_cgroup_prioidx() returning 1 if is not data and
sock_cgroup_classid() a 0?

thanks,
daniel
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