Re: [PATCH 0/5] Make SCSI device suspend work reliably

[Ming Lei <ming.lei@redhat.com>]

On Mon, Sep 11, 2017 at 04:25:30PM +0000, Bart Van Assche wrote:
> On Sat, 2017-09-09 at 18:39 +0800, Ming Lei wrote:
> > - the issue is not suspend/resume only, it is about SCSI quiesce vs.
> > RQF_PREEMPT.
> 
> The only in-kernel user of the SCSI quiesce/resume functionality next to
> runtime power management I know of is the SPI transport, namely
> spi_dv_device(). Nobody has ever reported a hang in spi_dv_device() as far
> as I know. Since the number of users of the SCSI parallel transport is very
> small I propose to wait with fixing spi_dv_device() until someone shows that
> it is possible to trigger that hang. If we have to address a hang in
> spi_dv_device() I propose to address it in the same way as my patch series
> addresses power management requests, namely by letting previously submitted
> requests complete and by making blk_get_request() callers wait until the
> quiesced SCSI device has been resumed.

As I mentioned in V4 cover letter, Cathy saw this I/O hang issue, and
she has verified that my revised patchset V3 can fix the issue.

> 
> > I don't see the issue above addressed by this patchset, so maybe
> > you are trying to fix another PM specific issue(not reported by
> > Oleksandr), I am just confused.
> 
> That's correct - I'm only trying to address the PM issues. I will mention
> that explicitly when I repost this patch series.

Unfortunately it isn't enough, and the approach you took is wrong too,
I will comment it in your patch 4.

-- 
Ming