linux-kernel - Re: [PATCH v4 08/14] res_counter: return amount of charges after res_counter

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Date:	Tue, 16 Oct 2012 17:20:34 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Glauber Costa <glommer@...allels.com>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Tejun Heo <tj@...nel.org>, cgroups@...r.kernel.org,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Greg Thelen <gthelen@...gle.com>, devel@...nvz.org,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH v4 08/14] res_counter: return amount of charges after
 res_counter_uncharge

(2012/10/08 19:06), Glauber Costa wrote:
> It is useful to know how many charges are still left after a call to
> res_counter_uncharge. While it is possible to issue a res_counter_read
> after uncharge, this can be racy.
> 
> If we need, for instance, to take some action when the counters drop
> down to 0, only one of the callers should see it. This is the same
> semantics as the atomic variables in the kernel.
> 
> Since the current return value is void, we don't need to worry about
> anything breaking due to this change: nobody relied on that, and only
> users appearing from now on will be checking this value.
> 
> Signed-off-by: Glauber Costa <glommer@...allels.com>
> CC: Michal Hocko <mhocko@...e.cz>
> CC: Johannes Weiner <hannes@...xchg.org>
> CC: Suleiman Souhlal <suleiman@...gle.com>
> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> ---
>   Documentation/cgroups/resource_counter.txt |  7 ++++---
>   include/linux/res_counter.h                | 12 +++++++-----
>   kernel/res_counter.c                       | 20 +++++++++++++-------
>   3 files changed, 24 insertions(+), 15 deletions(-)

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>



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