Re: [linus:master] [mm] 24e44cc22a: BUG:KCSAN:data-race_in_pcpu_alloc_noprof/pcpu_block_update_hint_alloc

[Tejun Heo]

On Mon, Jul 22, 2024 at 10:47:30AM -0700, Boqun Feng wrote:
> This looks like a data race because we read pcpu_nr_empty_pop_pages out
> of the lock for a best effort checking, @Tejun, maybe you could confirm
> on this?

That does sound plausible.

> -       if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
> +       /*
> +        * Checks pcpu_nr_empty_pop_pages out of the pcpu_lock, data races may
> +        * occur but this is just a best-effort checking, everything is synced
> +        * in pcpu_balance_work.
> +        */
> +       if (data_race(pcpu_nr_empty_pop_pages) < PCPU_EMPTY_POP_PAGES_LOW)
>                 pcpu_schedule_balance_work();

Would it be better to use READ/WRITE_ONCE() for the variable?

Thanks.

-- 
tejun