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Subject: Re: [PATCH 3/3] kref: Remove the memory barriers
From: Peter Zijlstra <peterz@infradead.org>
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: Mon, 12 Dec 2011 09:55:57 +0100
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On Mon, 2011-12-12 at 11:48 +0800, Ming Lei wrote:
> We can't assume any lock about kref usage, because kref is often used
> in lockless scenario. 

Then you're doing it wrong, seriously.

kref in lockless scenarios simply doesn't work, you need rcu (or another
means to stabilize storage) and atomic_inc_not_zero() as well as means
to validate your object after the lookup.