linux-kernel - Re: Containers: css

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Date:	Tue, 17 Jul 2007 10:44:08 -0700
From:	"Paul (宝瑠) Menage" 
	<menage@...gle.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	dhaval@...ux.vnet.ibm.com, "Pavel Emelianov" <xemul@...ru>,
	"linux kernel mailing list" <linux-kernel@...r.kernel.org>,
	"Paul Jackson" <pj@....com>,
	"Linux Containers" <containers@...ts.osdl.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: Containers: css_put() dilemma

On 7/17/07, Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
>
> That sounds correct. I wonder now if the solution should be some form
> of delegation for deletion of unreferenced containers (HINT: work queue
> or kernel threads).

What a great idea. In fact, that's exactly what the release agent
patch already does.

>
> > Adding a synchronize_rcu in container_diput() guarantees that the
> > container structure won't be freed while someone may still be
> > accessing it.
> >
>
> Do we take rcu_read_lock() in css_put() path or use call_rcu() to
> free the container?

Good point, we ought to add rcu_read_lock() (even though it doesn't
actually do anything on architectures other than alpha, right?)

Using call_rcu to do the container kfree rather than synchronize_rcu()
would be a possible future optimization, yes.

Paul
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