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Subject: Re: [PATCH 3/3] kref: Remove the memory barriers
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Ming Lei <tom.leiming@gmail.com>
Cc: gregkh@suse.de, akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        ostrikov@nvidia.com, adobriyan@gmail.com, eric.dumazet@gmail.com,
        mingo@elte.hu, Oliver Neukum <oneukum@suse.de>
Date: Sat, 10 Dec 2011 15:58:04 +0100
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On Sat, 2011-12-10 at 22:07 +0800, Ming Lei wrote:
> > While true, it fails to show why this is a problem. I say it is not a
> 
> IMO, the added two barriers are pairs of the implicit barrier in kref_put, so
> that we can order between kref_init/kref_get and kref_put. 

Yeah so? If there's a destruction race with kref_put() the barrier won't
solve it. Other than that the actual order of get/put is irrelevant.