linux-kernel - Re: [PATCH v2 6/6] percpu-refcount: implement percpu_ref_reinit() and percpu_ref_is

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Message-ID: <20140619190649.GB7390@mtj.dyndns.org>
Date:	Thu, 19 Jun 2014 15:06:49 -0400
From:	Tejun Heo <tj@...nel.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>, cl@...ux-foundation.org,
	kmo@...erainc.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/6] percpu-refcount: implement percpu_ref_reinit()
 and percpu_ref_is_zero()

On Thu, Jun 19, 2014 at 10:03:05AM -0700, Paul E. McKenney wrote:
> documentation: Add acquire/release barriers to pairing rules
> 
> It is possible to pair acquire and release barriers with other barriers,
> so this commit adds them to the list in the SMP barrier pairing section.
> 
> Reported-by: Lai Jiangshan <laijs@...fujitsu.com>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
> diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
> index a6ca533a73fc..2a7c3c4fb53f 100644
> --- a/Documentation/memory-barriers.txt
> +++ b/Documentation/memory-barriers.txt
> @@ -757,10 +757,12 @@ SMP BARRIER PAIRING
>  When dealing with CPU-CPU interactions, certain types of memory barrier should
>  always be paired.  A lack of appropriate pairing is almost certainly an error.
>  
> -A write barrier should always be paired with a data dependency barrier or read
> -barrier, though a general barrier would also be viable.  Similarly a read
> -barrier or a data dependency barrier should always be paired with at least an
> -write barrier, though, again, a general barrier is viable:
> +A write barrier should always be paired with a data dependency barrier,
> +acquire barrier, release barrier, or read barrier, though a general
> +barrier would also be viable.  Similarly a read barrier or a data
> +dependency barrier should always be paired with at least a write barrier,
> +an acquire barrier, or a release barrier, though, again, a general
> +barrier is viable:

FWIW,

Reviewed-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun
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