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Date:   Tue, 5 Oct 2021 14:02:40 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Marco Elver <elver@google.com>
Cc:     "Paul E . McKenney" <paulmck@kernel.org>,
        Alexander Potapenko <glider@google.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Dmitry Vyukov <dvyukov@google.com>,
        Ingo Molnar <mingo@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Waiman Long <longman@redhat.com>,
        Will Deacon <will@kernel.org>, kasan-dev@googlegroups.com,
        linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, x86@kernel.org
Subject: Re: [PATCH -rcu/kcsan 16/23] locking/atomics, kcsan: Add
 instrumentation for barriers
Message-ID: <YVw+4McyFdvU7ZED@hirez.programming.kicks-ass.net>
References: <20211005105905.1994700-1-elver@google.com>
 <20211005105905.1994700-17-elver@google.com>
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On Tue, Oct 05, 2021 at 12:58:58PM +0200, Marco Elver wrote:
> @@ -59,6 +60,7 @@ atomic_add(int i, atomic_t *v)
>  static __always_inline int
>  atomic_add_return(int i, atomic_t *v)
>  {
> +	kcsan_mb();
>  	instrument_atomic_read_write(v, sizeof(*v));
>  	return arch_atomic_add_return(i, v);
>  }

This and others,.. is this actually correct? Should that not be
something like:

	kscan_mb();
	instrument_atomic_read_write(...);
	ret = arch_atomic_add_return(i, v);
	kcsan_mb();
	return ret;

?