From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Alan Stern <stern@rowland.harvard.edu>,
Martin Kepplinger <martin.kepplinger@puri.sm>
Cc: Bart Van Assche <bvanassche@acm.org>,
Can Guo <cang@codeaurora.org>,
martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel@puri.sm
Subject: Re: [PATCH] scsi: sd: add runtime pm to open / release
Date: Wed, 29 Jul 2020 11:29:09 -0700 [thread overview]
Message-ID: <1596047349.4356.84.camel@HansenPartnership.com> (raw)
In-Reply-To: <20200729182515.GB1580638@rowland.harvard.edu>
On Wed, 2020-07-29 at 14:25 -0400, Alan Stern wrote:
> On Wed, Jul 29, 2020 at 06:43:48PM +0200, Martin Kepplinger wrote:
[...]
> > > > --- a/drivers/scsi/scsi_error.c
> > > > +++ b/drivers/scsi/scsi_error.c
> > > > @@ -554,16 +554,8 @@ int scsi_check_sense(struct scsi_cmnd
> > > > *scmd)
> > > > * so that we can deal with it there.
> > > > */
> > > > if (scmd->device->expecting_cc_ua) {
> > > > - /*
> > > > - * Because some device does not queue
> > > > unit
> > > > - * attentions correctly, we carefully
> > > > check
> > > > - * additional sense code and qualifier
> > > > so as
> > > > - * not to squash media change unit
> > > > attention.
> > > > - */
> > > > - if (sshdr.asc != 0x28 || sshdr.ascq !=
> > > > 0x00)
> > > > {
> > > > - scmd->device->expecting_cc_ua =
> > > > 0;
> > > > - return NEEDS_RETRY;
> > > > - }
> > > > + scmd->device->expecting_cc_ua = 0;
> > > > + return NEEDS_RETRY;
> > >
> > > Well, yes, but you can't do this because it would lose us media
> > > change events in the non-suspend/resume case which we really
> > > don't want. That's why I was suggesting a new flag.
> > >
> > > James
> >
> > also if I set expecting_cc_ua in resume() only, like I did?
>
> That wouldn't make any difference. The information sent by your
> card reader has sshdr.asc == 0x28 and sshdr.ascq == 0x00 (you can see
> it in the log). So because of the code here in scsi_check_sense(),
> which you can't change, the Unit Attention sent by the card reader
> would not be retried even if you do set the flag in resume().
But if we had a new flag, like expecting_media_change, you could set
that in resume and we could condition the above test in the code on it
and reset it and do a retry if it gets set. I'm not saying we have to
do it this way, but it sounds like we have to do something in the
kernel, so I think the flag will become necessary but there might be a
bit of policy based dance around how it gets set in the kernel (to
avoid losing accurate media change events).
James
next prev parent reply other threads:[~2020-07-29 18:29 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 11:10 [PATCH] scsi: sd: add runtime pm to open / release Martin Kepplinger
2020-06-24 13:33 ` Bart Van Assche
2020-06-25 8:16 ` Martin Kepplinger
2020-06-25 14:52 ` Alan Stern
2020-06-26 3:53 ` Bart Van Assche
2020-06-26 15:07 ` Bart Van Assche
2020-06-26 15:44 ` Alan Stern
2020-06-28 2:37 ` Bart Van Assche
2020-06-28 13:10 ` Alan Stern
2020-06-29 9:42 ` Martin Kepplinger
2020-06-29 16:15 ` Alan Stern
2020-06-29 16:56 ` Bart Van Assche
2020-06-29 17:40 ` Alan Stern
2020-06-30 3:33 ` Martin Kepplinger
2020-06-30 13:38 ` Alan Stern
2020-06-30 15:59 ` Bart Van Assche
2020-06-30 18:02 ` Alan Stern
2020-06-30 19:23 ` Bart Van Assche
2020-06-30 19:38 ` Alan Stern
2020-06-30 23:31 ` Bart Van Assche
2020-07-01 0:49 ` Alan Stern
2020-07-06 16:41 ` Alan Stern
2020-07-28 7:02 ` Martin Kepplinger
2020-07-28 20:02 ` Alan Stern
2020-07-29 14:12 ` Martin Kepplinger
2020-07-29 14:32 ` Alan Stern
2020-07-29 14:44 ` Martin K. Petersen
2020-07-29 14:56 ` Alan Stern
2020-07-29 14:46 ` James Bottomley
2020-07-29 14:53 ` James Bottomley
2020-07-29 15:40 ` Martin Kepplinger
2020-07-29 15:44 ` James Bottomley
2020-07-29 16:43 ` Martin Kepplinger
2020-07-29 18:25 ` Alan Stern
2020-07-29 18:29 ` James Bottomley [this message]
2020-07-30 8:52 ` Martin Kepplinger
2020-07-30 8:54 ` Martin Kepplinger
2020-07-30 15:10 ` Alan Stern
2020-08-04 9:39 ` Martin Kepplinger
2020-08-07 9:51 ` Martin Kepplinger
2020-08-07 14:30 ` Alan Stern
2020-08-08 6:59 ` Martin Kepplinger
2020-08-08 15:05 ` Alan Stern
2020-08-09 9:20 ` Martin Kepplinger
2020-08-09 15:26 ` Alan Stern
2020-08-10 12:03 ` Martin Kepplinger
2020-08-10 14:13 ` Alan Stern
2020-08-11 7:55 ` Martin Kepplinger
2020-08-11 13:48 ` Alan Stern
2020-08-23 14:57 ` [PATCH] block: Fix bug in runtime-resume handling Alan Stern
2020-08-24 17:48 ` Bart Van Assche
2020-08-24 20:13 ` Alan Stern
2020-08-26 7:48 ` Martin Kepplinger
2020-08-27 17:42 ` Martin Kepplinger
2020-08-27 20:29 ` Alan Stern
2020-08-29 7:24 ` Martin Kepplinger
2020-08-29 15:26 ` Alan Stern
2020-08-29 16:33 ` Martin Kepplinger
2020-08-29 18:56 ` Alan Stern
2020-08-30 0:38 ` Bart Van Assche
2020-08-30 1:06 ` Alan Stern
2020-07-29 15:40 ` [PATCH] scsi: sd: add runtime pm to open / release Alan Stern
2020-07-29 15:49 ` James Bottomley
2020-07-29 16:17 ` Alan Stern
2020-07-29 15:52 ` Martin Kepplinger
2020-07-29 18:10 ` Douglas Gilbert
2020-07-30 8:05 ` Martin Kepplinger
2020-07-30 15:14 ` Alan Stern
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