On 08/15/2018 04:28 PM, Ming Lei wrote:
> On Wed, Aug 15, 2018 at 02:39:05PM +0800, jianchao.wang wrote:
>> Hi Ming
>>
>> On 08/11/2018 03:12 PM, Ming Lei wrote:
>>> @@ -3786,6 +3800,10 @@ int blk_pre_runtime_suspend(struct request_queue *q)
>>> q->rpm_status = RPM_SUSPENDING;
>>> }
>>> spin_unlock_irq(q->queue_lock);
>>> +
>>> + if (!ret)
>>> + blk_freeze_queue_lock(q);
>>> +
>>> return ret;
>>
>> Requests seem to be able enter the request_queue while the rpm_status is RPM_SUSPENDING
>> and miss the rpm_resume.
>
> Any requests which enters queue during RPM_SUSPENDING will be drained by
> blk_freeze_queue_lock().
>
>>
>> Even though blk_freeze_queue_lock will drain them before the real suspend start, but looks
>> like we should stop the suspend at the moment.
>
> Good point, even though it doesn't affect the correctness of this runtime PM
> implementation.
>
> We may improve this situation by the following way, what do you think of
> it?
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index f42197c9f7af..84e1e6c7db87 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -3803,10 +3803,13 @@ int blk_pre_runtime_suspend(struct request_queue *q)
> {
> int ret = 0;
> bool busy = true;
> + unsigned long last_busy;
>
> if (!q->dev)
> return ret;
>
> + last_busy = READ_ONCE(dev->power.last_busy);
> +
> if (q->mq_ops)
> busy = blk_mq_pm_queue_busy(q);
>
> @@ -3823,6 +3826,13 @@ int blk_pre_runtime_suspend(struct request_queue *q)
> if (!ret)
> blk_freeze_queue_lock(q);
>
> + /*
> + * Any new IO during this window will prevent the current suspend
> + * from going on
> + */
> + if (unlikely(last_busy != READ_ONCE(dev->power.last_busy)))
> + ret = -EBUSY;
> +
> return ret;
> }
> EXPORT_SYMBOL(blk_pre_runtime_suspend);
>
Wow, this is great method !
Maybe we should add checking as following:
+ last_busy = READ_ONCE(dev->power.last_busy);
+ if (last_busy == jiffies)
+ return -EBUSY
if (q->mq_ops)
busy = blk_mq_pm_queue_busy(q);
Thanks
Jianchao
> Thanks,
> Ming
>
