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From:   Alan Huang <mmpgouride@gmail.com>
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Subject: Question about the barrier() in hlist_nulls_for_each_entry_rcu()
Message-Id: <04C1E631-725C-47AD-9914-25D5CE04DFF4@gmail.com>
Date:   Fri, 21 Jul 2023 02:53:53 +0800
Cc:     "Paul E. McKenney" <paulmck@kernel.org>,
        Eric Dumazet <edumazet@google.com>, roman.gushchin@linux.dev
To:     linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        rcu@vger.kernel.org
Precedence: bulk

Hi,

I noticed a commit c87a124a5d5e(=E2=80=9Cnet: force a reload of first =
item in hlist_nulls_for_each_entry_rcu=E2=80=9D)
and a related discussion [1].

After reading the whole discussion, it seems like that ptr->field was =
cached by gcc even with the deprecated
ACCESS_ONCE(), so my question is:

	Is that a compiler bug? If so, has this bug been fixed today, =
ten years later?=20
=09
	What about READ_ONCE(ptr->field)?


[1] =
https://lore.kernel.org/all/1369699930.3301.494.camel@edumazet-glaptop/

Thanks,
Alan=