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From: Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: [GIT PULL] overlay filesystem v25
Date: Tue, 28 Oct 2014 01:12:14 +0000
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Cc: Miklos Szeredi <miklos@szeredi.hu>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
	Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-unionfs@vger.kernel.org
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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On Mon, Oct 27, 2014 at 10:36:21AM -0700, Paul E. McKenney wrote:
> Code making direct use of smp_read_barrier_depends() is harder to read,
> in my experience, but good point on the sparse noise.  Maybe a new
> lockless_dereference() primitive?  Maybe something like the following?
> (Untested, probably does not even build.)
> 
> #define lockless_dereference(p) \
> ({ \
> 	typeof(*p) *_________p1 = ACCESS_ONCE(p); \
> 	smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
> 	_________p1; \
> })

Hmm...  Where would you prefer to put it?  rcupdate.h?