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

["jianchao.wang" <jianchao.w.wang@oracle.com>]

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