Re: [PATCH] selftests/sched_ext: Fix build error in dequeue_remote selftest

[Kuba Piecuch <jpiecuch@google.com>]

On Mon Oct 12, 2026 at 11:59 AM UTC, Samuele Mariotti wrote:
> Building the dequeue_remote selftest with newer compilers (e.g., gcc 16)
> triggers the following error:
>
> dequeue_remote.c:39:32: error: variable ‘sum’ set but not used
>
> The 'volatile' qualifier prevents the writes from being optimized away,
> but does not silence the warning, since 'sum' is indeed only written and
> never read.
>
> Consume 'sum' via an empty asm() with a register input constraint, as
> already done for the dequeue selftest in commit 3788e3251653
> ("selftests/sched_ext: Fix build error in dequeue selftest"). This forces
> the compiler to keep the accumulated value (preserving the CPU stress loop)
> and avoids the build error.
>
> Fixes: cc07fae1de5d ("selftests/sched_ext: Add a test for ops.dequeue() on remote local DSQ moves")
>
> Signed-off-by: Samuele Mariotti <smariotti@disroot.org>
> ---
>  tools/testing/selftests/sched_ext/dequeue_remote.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/tools/testing/selftests/sched_ext/dequeue_remote.c b/tools/testing/selftests/sched_ext/dequeue_remote.c
> index f2c1901030de..af344581d5f1 100644
> --- a/tools/testing/selftests/sched_ext/dequeue_remote.c
> +++ b/tools/testing/selftests/sched_ext/dequeue_remote.c
> @@ -43,6 +43,7 @@ static void worker_fn(int id)
>  
>  		for (j = 0; j < 20000 + id * 1000; j++)
>  			sum += j;
> +		asm volatile("" : : "r"(sum));
>  		if (id & 1)
>  			usleep(100);
>  		else

LGTM, thank you Samuele!

Reviewed-by: Kuba Piecuch <jpiecuch@google.com>