Re: [PATCH 2/2] Make res_counter hierarchical

[Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

YAMAMOTO Takashi wrote:
>> @@ -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?

The res_counter client must provide this. Currently cgroup subsystem does this.

> YAMAMOTO Takashi
>