linux-kernel - Re: [PATCH v5 08/14] res_counter: return amount of charges after res_counter

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Date:	Wed, 17 Oct 2012 16:23:19 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Glauber Costa <glommer@...allels.com>
cc:	linux-mm@...ck.org, cgroups@...r.kernel.org,
	Mel Gorman <mgorman@...e.de>, Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	kamezawa.hiroyu@...fujitsu.com, Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>, devel@...nvz.org,
	linux-kernel@...r.kernel.org,
	Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [PATCH v5 08/14] res_counter: return amount of charges after
 res_counter_uncharge

On Tue, 16 Oct 2012, 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>
> Reviewed-by: Michal Hocko <mhocko@...e.cz>
> Acked-by: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> CC: Johannes Weiner <hannes@...xchg.org>
> CC: Suleiman Souhlal <suleiman@...gle.com>
> CC: Tejun Heo <tj@...nel.org>

Acked-by: David Rientjes <rientjes@...gle.com>
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