From mboxrd@z Thu Jan  1 00:00:00 1970
From: peterz@infradead.org (Peter Zijlstra)
Date: Mon, 20 Nov 2017 20:28:06 +0100
Subject: [PATCH v2 18/18] arm64: select ARCH_SUPPORTS_LTO_CLANG
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To: linux-arm-kernel@lists.infradead.org
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On Mon, Nov 20, 2017 at 06:05:55PM +0000, Will Deacon wrote:
> This is a thorny issue, but RCU (specifically rcu_dereference but probably
> also some READ_ONCEs) relies on being able to utilise syntactic dependency
> chains to order local accesses to shared variables.

Well, we used to have READ_ONCE() and smp_read_barrier_depends(), but
we recently munged them together, in the process getting rid of
lockless_dereference().

So for sure, READ_ONCE() must be able to do the address dependency
thing, otherwise tons of code comes apart.