netdev - Re: [PATCH net] soreuseport: use RCU_INIT

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Message-ID: <20181213033526.athxdsztxsknebhs@bogon>
Date:   Thu, 13 Dec 2018 11:35:32 +0800
From:   Xiaozhou Liu <liuxiaozhou@...edance.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net] soreuseport: use RCU_INIT_POINTER() when NULLing

On Wed, Dec 12, 2018 at 05:08:45AM -0800, Eric Dumazet wrote:

> 
> It is _not_ faster.
> 
> Just different ways to do the exact same thing.
> 
> For some reason you missed this two years old commit :
> 
> 
> commit 3a37f7275cda5ad25c1fe9be8f20c76c60d175fa
> Author: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Date:   Sun May 1 18:46:54 2016 -0700
> 
>     rcu: No ordering for rcu_assign_pointer() of NULL
>     
>     This commit does a compile-time check for rcu_assign_pointer() of NULL,
>     and uses WRITE_ONCE() rather than smp_store_release() in that case.
>     
>     Reported-by: Christoph Hellwig <hch@...radead.org>
>     Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

Thanks for pointing this out. I guess the comments in include/linux/rcupdate.h
may need some updating.

Xiaozhou