2023年7月21日 03:22，Eric Dumazet [off-list ref] 写道：

On Thu, Jul 20, 2023 at 8:54 PM Alan Huang [off-list ref] wrote:

quoted

Hi,

I noticed a commit c87a124a5d5e(“net: force a reload of first item in hlist_nulls_for_each_entry_rcu”)
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?

       What about READ_ONCE(ptr->field)?

Make sure sparse is happy.

It caused a problem without barrier(), and the deprecated ACCESS_ONCE() didn’t help:

	https://lore.kernel.org/all/519D19DA.50400@yandex-team.ru/ (local)

So, my real question is: With READ_ONCE(ptr->field), are there still some unusual cases where gcc 
decides not to reload ptr->field?

Do you have a patch for review ?

Possibly next month. :)

quoted

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

Thanks,
Alan