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SubjectRe: [PATCH 5/8] membarrier, kthread: Use _ONCE accessors for task->mm
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On 6/16/21 11:08 AM, Mathieu Desnoyers wrote:
> ----- On Jun 15, 2021, at 11:21 PM, Andy Lutomirski luto@kernel.org wrote:
>
>> membarrier reads cpu_rq(remote cpu)->curr->mm without locking. Use
>> READ_ONCE() and WRITE_ONCE() to remove the data races.
>
> I notice that kernel/exit.c:exit_mm() also has:
>
> current->mm = NULL;
>
> I suspect you may want to add a WRITE_ONCE() there as well ?

Good catch. I was thinking that exit_mm() couldn't execute concurrently
with membarrier(), but that's wrong.

--Andy

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