Re: [PATCH v4 1/2] bpf: avoid grabbing spin_locks of all cpus when no free elems

[Alexei Starovoitov]

On Wed, Jun 1, 2022 at 10:42 AM Feng zhou <zhoufeng.zf@xxxxxxxxxxxxx> wrote:
>
>  static inline void ___pcpu_freelist_push(struct pcpu_freelist_head *head,
> @@ -130,14 +134,19 @@ static struct pcpu_freelist_node *___pcpu_freelist_pop(struct pcpu_freelist *s)
>         orig_cpu = cpu = raw_smp_processor_id();
>         while (1) {
>                 head = per_cpu_ptr(s->freelist, cpu);
> +               if (READ_ONCE(head->is_empty))
> +                       goto next_cpu;
>                 raw_spin_lock(&head->lock);
>                 node = head->first;
>                 if (node) {

extra bool is unnecessary.
just READ_ONCE(head->first)