[PATCH 4/5] rust: hrtimer: use READ_ONCE instead of read_volatile

[John Hubbard]

On 1/6/26 5:08 PM, Boqun Feng wrote:
> On Tue, Jan 06, 2026 at 04:47:35PM -0800, John Hubbard wrote:
>> On 1/6/26 10:43 AM, Alice Ryhl wrote:
>>> On Tue, Jan 06, 2026 at 03:23:00PM +0000, Gary Guo wrote:
>>>> On Tue, 06 Jan 2026 13:37:34 +0100
>>>> Andreas Hindborg <a.hindborg at kernel.org> wrote:
>>>>> "FUJITA Tomonori" <fujita.tomonori at gmail.com> writes:
...
>>>>> This is a potentially racy read. As far as I recall, we determined that
>>>>> using read_once is the proper way to handle the situation.
>>>>>
>>>>> I do not think it makes a difference that the read is done by C code.
>>>>
>>>> If that's the case I think the C code should be fixed by inserting the
>>>> READ_ONCE?
>>>
>>> I maintain my position that if this is what you recommend C code does,
>>> it's confusing to not make the same recommendation for Rust abstractions
>>> to the same thing.
>>>
>>> After all, nothing is stopping you from calling atomic_read() in C too.
>>>
>>
>> Hi Alice and everyone!
>>
>> I'm having trouble fully understanding the latest reply, so maybe what
>> I'm saying is actually what you just said.
>>
>> Anyway, we should use READ_ONCE in both the C and Rust code. Relying
>> on the compiler for that is no longer OK. We shouldn't be shy about
>> fixing the C side (not that I think you have been, so far!).
>>
> 
> Agreed on most of it, except that we should be more explicit in Rust,
> by using atomic_load[1] instead of READ_ONCE().
> 
> [1]: https://lore.kernel.org/rust-for-linux/aV0FxCRzXFrNLZik@tardis-2.local/
> 

I see. That does put things in a much clearer state, yes.

thanks,
-- 
John Hubbard