Re: [PATCH 2/2] Make res_counter hierarchical

[yamamoto-jCdQPDEk3idL9jVzuh4AOg@public.gmane.org (YAMAMOTO Takashi)]

> @@ -36,10 +37,26 @@ int res_counter_charge(struct res_counter *counter, unsigned long val)
>  {
>  	int ret;
>  	unsigned long flags;
> +	struct res_counter *c, *unroll_c;
> +
> +	local_irq_save(flags);
> +	for (c = counter; c != NULL; c = c->parent) {
> +		spin_lock(&c->lock);
> +		ret = res_counter_charge_locked(c, val);
> +		spin_unlock(&c->lock);
> +		if (ret < 0)
> +			goto unroll;
> +	}
> +	local_irq_restore(flags);
> +	return 0;
>  
> -	spin_lock_irqsave(&counter->lock, flags);
> -	ret = res_counter_charge_locked(counter, val);
> -	spin_unlock_irqrestore(&counter->lock, flags);
> +unroll:
> +	for (unroll_c = counter; unroll_c != c; unroll_c = unroll_c->parent) {
> +		spin_lock(&unroll_c->lock);
> +		res_counter_uncharge_locked(unroll_c, val);
> +		spin_unlock(&unroll_c->lock);
> +	}
> +	local_irq_restore(flags);
>  	return ret;
>  }

what prevents the topology (in particular, ->parent pointers) from
changing behind us?

YAMAMOTO Takashi