Re: [PATCH] drm/i915: replace fetch_and_zero() with kernel xchg()

[Sebastian Brzezinka <sebastian.brzezinka@intel.com>]

Hi Jani,

On Mon Apr 27, 2026 at 2:26 PM CEST, Jani Nikula wrote:
> On Mon, 27 Apr 2026, Sebastian Brzezinka <sebastian.brzezinka@intel.com> wrote:
>> The i915 local fetch_and_zero() macro is a non-atomic
>> fetch-and-zero operation defined in i915_utils.h and duplicated in
>> display/intel_display_utils.h. Its functionality is equivalent to the
>> kernel-provided xchg().
>
> While I dislike having the local fetch_and_zero() macro around, the
> usage does not need to be atomic, and there's no need to switch to the
> atomic xchg() at all.
>
> Using atomic xchg() gives the wrong impression to the reader that the
> atomicity matters when it doesn't.
>
> So that's a no for this patch.
>
> There's been a few attempts at fixing this in the past, one I found was
> [1].
>
> [1] https://lore.kernel.org/r/20221209154843.4162814-1-andrzej.hajda@intel.com
Thank you for the clarification. It’s good to know.

>> Replace fetch_and_zero() with the kernel provided xchg(), and
>> remove the now unused macro definitions from both i915_utils.h and
>> display/intel_display_utils.h.
>>
>> Reviewed-by: Krzysztof Karas <krzysztof.karas@intel.com>
>
> Where did this happen? Was there a v1? Is this v2?
This patch was initially sent to trybot and received Review-by: Krzysztof
there. So I’ve copied it here.


-- 
Best regards,
Sebastian