RE: [PATCH v3 1/1] scsi: pm: Balance pm_only counter of request queue during system resume

[Avri Altman]

> 
> On 2020-04-29 21:10, Can Guo wrote:
> > During system resume, scsi_resume_device() decreases a request queue's
> > pm_only counter if the scsi device was quiesced before. But after that,
> > if the scsi device's RPM status is RPM_SUSPENDED, the pm_only counter is
> > still held (non-zero). Current scsi resume hook only sets the RPM status
> > of the scsi device and its request queue to RPM_ACTIVE, but leaves the
> > pm_only counter unchanged. This may make the request queue's pm_only
> > counter remain non-zero after resume hook returns, hence those who are
> > waiting on the mq_freeze_wq would never be woken up. Fix this by calling
> > blk_post_runtime_resume() if pm_only is non-zero to balance the pm_only
> > counter which is held by the scsi device's RPM ops.
> 
> How was this issue discovered? How has this patch been tested?

I think this insight was originally gained as part of commit fb276f770118
(scsi: ufs: Enable block layer runtime PM for well-known logical units)

But I will let Can reply on that.

Thanks,
Avri

> 
> Thanks,
> 
> Bart.