linux-kernel - Re: [PATCH v4 4/8] per-cgroup tcp buffers control

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Date:	Tue, 4 Oct 2011 10:16:33 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Glauber Costa <glommer@...allels.com>
Cc:	linux-kernel@...r.kernel.org, paul@...lmenage.org,
	lizf@...fujitsu.com, ebiederm@...ssion.com, davem@...emloft.net,
	gthelen@...gle.com, netdev@...r.kernel.org, linux-mm@...ck.org,
	kirill@...temov.name, avagin@...allels.com
Subject: Re: [PATCH v4 4/8] per-cgroup tcp buffers control

On Mon,  3 Oct 2011 14:18:39 +0400
Glauber Costa <glommer@...allels.com> wrote:

> With all the infrastructure in place, this patch implements
> per-cgroup control for tcp memory pressure handling.
> 
> Signed-off-by: Glauber Costa <glommer@...allels.com>
> CC: David S. Miller <davem@...emloft.net>
> CC: Hiroyouki Kamezawa <kamezawa.hiroyu@...fujitsu.com>
> CC: Eric W. Biederman <ebiederm@...ssion.com>

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujtisu.com>

One question.
> +void tcp_enter_memory_pressure(struct sock *sk)
> +{
> +	struct mem_cgroup *memcg = sk->sk_cgrp;
> +	if (!memcg->tcp.tcp_memory_pressure) {
> +		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMEMORYPRESSURES);
> +		memcg->tcp.tcp_memory_pressure = 1;
> +	}
> +}

It seems memcg->tcp.tcp_memory_pressure has no locks and not atomic.

no problematic race ?

Thanks,
-Kame

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