Re: [PATCH] SCSI: don't get target/host busy_count in scsi_mq_get_budget()

Ming Lei
2017-11-08T02:58:39Z

On Tue, Nov 07, 2017 at 07:55:32PM -0700, Jens Axboe wrote:
> On 11/07/2017 05:39 PM, Ming Lei wrote:
> > On Tue, Nov 07, 2017 at 04:20:08PM +0000, Bart Van Assche wrote:
> >> On Tue, 2017-11-07 at 10:11 +0800, Ming Lei wrote:
> >>> If you can reproduce, please provide me at least the following log
> >>> first:
> >>>
> >>> find /sys/kernel/debug/block -name tags | xargs cat | grep busy
> >>>
> >>> If any pending requests arn't completed, please provide the related
> >>> info in dbgfs about where is the request.
> >>
> >> Every time I ran the above or a similar command its output was empty. I
> >> assume that's because the hang usually occurs in a phase where these debugfs
> >> attributes either have not yet been created or have already disappeared.
> >
> > Could you dump all tags? Then you can see if this attribute is disappeared.
> >
> > If that output is empty, it often means there isn't pending request not
> > completed. So if that is true, your hang is _not_ related with RESTART.
>
> You need to check sched_tags as well. It could still be a restart race
> or problem, if tags is empty but sched_tags has busy bits.

Yeah, I didn't mention because SRP is MQ hardware, and the default
scheduler is none, but if Bart changes that, the sched_tags need to
checked first.

--
Ming