Re: [PATCH v19 2/3] scsi: ufs: L2P map management for HPB read

[Can Guo <cang@codeaurora.org>]

On 2021-02-08 16:03, Daejun Park wrote:
>> @@ -342,13 +1208,14 @@ void ufshpb_suspend(struct ufs_hba *hba)
>> >  	struct scsi_device *sdev;
>> >
>> >  	shost_for_each_device(sdev, hba->host) {
>> > -		hpb = sdev->hostdata;
>> > +		hpb = ufshpb_get_hpb_data(sdev);
>> >  		if (!hpb)
>> >  			continue;
>> >
>> >  		if (ufshpb_get_state(hpb) != HPB_PRESENT)
>> >  			continue;
>> >  		ufshpb_set_state(hpb, HPB_SUSPEND);
>> > +		ufshpb_cancel_jobs(hpb);
>> 
>> Here may have a dead lock problem - in the case of runtime suspend,
>> when ufshpb_suspend() is invoked, all of hba's children scsi devices
>> are in RPM_SUSPENDED state. When this line tries to cancel a running
>> map work, i.e. when ufshpb_get_map_req() calls below lines, it will
>> be stuck at blk_queue_enter().
>> 
>> req = blk_get_request(hpb->sdev_ufs_lu->request_queue,
>> 		      REQ_OP_SCSI_IN, 0);
>> 
>> Please check block layer power management, and see also commit 
>> d55d15a33
>> ("scsi: block: Do not accept any requests while suspended").
> 
> I am agree with your comment.
> How about add BLK_MQ_REQ_NOWAIT flag on blk_get_request() to avoid 
> hang?
> 

That won't work - BLK_MQ_REQ_NOWAIT allows one to fast fail from 
blk_mq_get_tag(),
but blk_queue_enter() comes before __blk_mq_alloc_request();

Regards,

Can Guo.

> Thanks,
> Daejun