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Date: Mon, 20 Nov 2017 20:28:06 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will.deacon@arm.com>
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Subject: Re: [PATCH v2 18/18] arm64: select ARCH_SUPPORTS_LTO_CLANG
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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.