linux-kernel - Re: [PATCH] rculist: list_first_or_null_rcu() should use list_entry

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Message-ID: <20130626152553.GB4405@mtj.dyndns.org>
Date:	Wed, 26 Jun 2013 08:25:53 -0700
From:	Tejun Heo <tj@...nel.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Dipankar Sarma <dipankar@...ibm.com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Li Zefan <lizefan@...wei.com>,
	Patrick McHardy <kaber@...sh.net>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rculist: list_first_or_null_rcu() should use
 list_entry_rcu()

On Wed, Jun 26, 2013 at 07:17:52AM -0700, Paul E. McKenney wrote:
> > Do you mean something like the following?
> > 
> > 	  struct list_head *__next = ACCESS_ONCE(__ptr->next); \
> > 	  likely(__ptr != __next) ? \
> > 		list_entry_rcu(__next, type, member) : NULL; \
> > 
> > Yeah, that looks right to me.
> 
> I would feel much better about this!  Does it avoid warnings in your
> use cases?

Yeah, it does, and more importantly it adds the missing read barrier
during RCU deref.  I'll give it another test and post the updated
version.

Thanks a lot!

-- 
tejun
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