From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>
Subject: Re: [RFC][PATCH 2/4] res_counter check usage under val
Date: Mon, 21 Jul 2008 21:41:35 +0400
Message-ID: <4884CA4F.9060003@openvz.org>
References: <20080718193123.cf74b574.kamezawa.hiroyu@jp.fujitsu.com>
	<20080718193530.578fb1e3.kamezawa.hiroyu@jp.fujitsu.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
In-Reply-To: <20080718193530.578fb1e3.kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
List-Unsubscribe: <https://lists.linux-foundation.org/mailman/listinfo/containers>,
	<mailto:containers-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=unsubscribe>
List-Archive: <http://lists.linux-foundation.org/pipermail/containers>
List-Post: <mailto:containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
List-Help: <mailto:containers-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=help>
List-Subscribe: <https://lists.linux-foundation.org/mailman/listinfo/containers>,
	<mailto:containers-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=subscribe>
Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
Cc: "yamamoto-jCdQPDEk3idL9jVzuh4AOg@public.gmane.org" <yamamoto-jCdQPDEk3idL9jVzuh4AOg@public.gmane.org>, "nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org" <nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org>, "kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org" <kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org>, "containers-qjLDD68F18O7TbgM5vRIOg@public.gmane.org" <containers-qjLDD68F18O7TbgM5vRIOg@public.gmane.org>, "menage-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org" <menage-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, "balbir-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org" <balbir-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
List-Id: containers.vger.kernel.org

KAMEZAWA Hiroyuki wrote:
> Add an interface to check usage is below "val"
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
> 
>  include/linux/res_counter.h |   13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> Index: mmtom-stamp-2008-07-15-15-39/include/linux/res_counter.h
> ===================================================================
> --- mmtom-stamp-2008-07-15-15-39.orig/include/linux/res_counter.h
> +++ mmtom-stamp-2008-07-15-15-39/include/linux/res_counter.h
> @@ -191,4 +191,17 @@ static inline int res_counter_set_limit(
>  	return ret;
>  }
>  
> +static inline int res_counter_check_under_val(struct res_counter *cnt,
> +	unsigned long long val)
> +{
> +	unsigned long flags;
> +	int ret = 0;
> +
> +	spin_lock_irqsave(&cnt->flags, flags);

Is this spilock protection *really* required? As far as I see
from its usage it is racy itself wrt to res_counter update, so 
this locking looks superfluous.

> +	if (cnt->usage < val)
> +		ret = 1;
> +	spin_unlock_irqrestore(&cnt->flags, flags);
> +	return ret;
> +}
> +
>  #endif
> 
>