Re: [PATCH] bpf: replace pop/push emptiness check with bpf_list_empty()

[Emil Tsalapatis]

On Sat May 23, 2026 at 2:34 PM EDT, Suchit Karunakaran wrote:
> Simplify fq_flows_is_empty() by replacing the pop/push based emptiness
> check with a direct call to bpf_list_empty().
> This avoids unnecessary list mutation and simplifies the code while
> preserving correctness.
>
> Signed-off-by: Suchit Karunakaran <suchitkarunakaran@xxxxxxxxx>

Imo the new code is way nicer, so even if this is a selftest the change
is worth it. After addressing the AI feedback feel free to add:

Reviewed-by: Emil Tsalapatis <emil@xxxxxxxxxxxxxxx>

> ---
>  tools/testing/selftests/bpf/progs/bpf_qdisc_fq.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fq.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fq.c
> index 1a3233a275c7..3b05ac1d7c77 100644
> --- a/tools/testing/selftests/bpf/progs/bpf_qdisc_fq.c
> +++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fq.c
> @@ -197,17 +197,13 @@ static bool
>  fq_flows_is_empty(struct bpf_list_head *head, struct bpf_spin_lock *lock)
>  {
>  	struct bpf_list_node *node;
> +	bool empty;
>  
>  	bpf_spin_lock(lock);
> -	node = bpf_list_pop_front(head);
> -	if (node) {
> -		bpf_list_push_front(head, node);
> -		bpf_spin_unlock(lock);
> -		return false;
> -	}
> +	empty = bpf_list_empty(head);
>  	bpf_spin_unlock(lock);
>  
> -	return true;
> +	return empty;
>  }
>  
>  /* flow->age is used to denote the state of the flow (not-detached, detached, throttled)