On Thu, Aug 25, 2022 at 07:44:16PM -0700, Alexei Starovoitov wrote:
> +/* Mostly runs from irq_work except __init phase. */
> +static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node)
> +{
> + struct mem_cgroup *memcg = NULL, *old_memcg;
> + unsigned long flags;
> + void *obj;
> + int i;
> +
> + memcg = get_memcg(c);
> + old_memcg = set_active_memcg(memcg);
> + for (i = 0; i < cnt; i++) {
> + obj = __alloc(c, node);
> + if (!obj)
> + break;
> + if (IS_ENABLED(CONFIG_PREEMPT_RT))
> + /* In RT irq_work runs in per-cpu kthread, so disable
> + * interrupts to avoid preemption and interrupts and
> + * reduce the chance of bpf prog executing on this cpu
> + * when active counter is busy.
> + */
> + local_irq_save(flags);
> + if (local_inc_return(&c->active) == 1) {
Is it because it is always '== 1' here so that there is
no need to free the obj when it is '!= 1' ?
> + __llist_add(obj, &c->free_llist);
> + c->free_cnt++;
> + }
> + local_dec(&c->active);
> + if (IS_ENABLED(CONFIG_PREEMPT_RT))
> + local_irq_restore(flags);
> + }
> + set_active_memcg(old_memcg);
> + mem_cgroup_put(memcg);
> +}
