Re: [PATCH v5 5/9] block: Change the runtime power management approach (1/2)

[jianchao.wang]

On 08/08/2018 02:11 PM, jianchao.wang wrote:
> Hi Bart
> 
> On 08/08/2018 06:51 AM, Bart Van Assche wrote:
>> @@ -391,6 +393,9 @@ static struct request *blk_mq_get_request(struct 
>> request_queue *q,
>>              }
>>      }
>>      data->hctx->queued++;
>> +
>> +    blk_pm_add_request(q, rq);
>> +
>>      return rq;
>>  }
> 
> The request_queue is in pm_only mode when suspended, who can reach here to do 
> the resume ?

I mean, in the original blk-legacy runtime pm implementation, any new IO could 
trigger the resume,
after your patch set, only the pm request could pass the blk_queue_enter while 
the queue is suspended
and in pm-only mode. But if no resume, where does the pm request come from ?

The blk_pm_add_request should be added to blk_queue_enter.
It looks like as following:
   1. when an normal io reaches blk_queue_enter, if queue is in suspended mode, 
it invoke blk_pm_add_request
      to trigger the resume, then wait here for the pm_only mode to be cleared.
   2. the runtime pm core does the resume work and clear the pm_only more 
finally
   3. the task blocked in blk_queue_enter is waked up and proceed.

Thanks
Jianchao