Linux-SCSI Archive on lore.kernel.org
 help / color / Atom feed
From: Alan Stern <stern@rowland.harvard.edu>
To: Martin Kepplinger <martin.kepplinger@puri.sm>
Cc: Bart Van Assche <bvanassche@acm.org>,
	jejb@linux.ibm.com, 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: Thu, 30 Jul 2020 11:14:05 -0400
Message-ID: <20200730151405.GC6332@rowland.harvard.edu> (raw)
In-Reply-To: <c253dde7-9347-b3dc-9c91-65d685793b29@puri.sm>

On Thu, Jul 30, 2020 at 10:05:50AM +0200, Martin Kepplinger wrote:
> On 29.06.20 18:15, Alan Stern wrote:
> > On Mon, Jun 29, 2020 at 11:42:59AM +0200, Martin Kepplinger wrote:
> >>
> >>
> >> On 26.06.20 17:44, Alan Stern wrote:
> >>> Martin's best approach would be to add some debugging code to find out why 
> >>> blk_queue_enter() isn't calling bkl_pm_request_resume(), or why that call 
> >>> doesn't lead to pm_request_resume().
> >>>
> >>> Alan Stern
> >>>
> >>
> >> Hi Alan,
> >>
> >> blk_queue_enter() always - especially when sd is runtime suspended and I
> >> try to mount as above - sets success to be true for me, so never
> >> continues down to bkl_pm_request_resume(). All I see is "PM: Removing
> >> info for No Bus:sda1".
> > 
> > Aha.  Looking at this more closely, it's apparent that the code in 
> > blk-core.c contains a logic bug: It assumes that if the BLK_MQ_REQ_PREEMPT 
> > flag is set then the request can be issued regardless of the queue's 
> > runtime status.  That is not correct when the queue is suspended.
> > 
> > Below is my attempt to fix this up.  I'm not sure that the patch is 
> > entirely correct, but it should fix this logic bug.  I would appreciate a 
> > critical review.
> > 
> > Martin, does this fix the problem?
> > 
> > Alan Stern
> 
> Hi Alan,
> 
> So in the block layer your change below indeed fixes the problem and if
> you want to submit that 1:1 feel free to add
> 
> Tested-by: Martin Kepplinger <martin.kepplinger@puri.sm>
> 
> thanks for your help in this!

Thank you for _your_ help!

The next merge window is coming up soon.  I think I'll wait until it is 
over before submitting the patch (maintainers tend to be too busy to 
consider new patches during a merge window).

But I am still open to comments or criticism of the patch in the 
meantime.  There hasn't been any feedback since Bart's initial set of 
questions.

Alan Stern

      reply index

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23 11:10 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
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 [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200730151405.GC6332@rowland.harvard.edu \
    --to=stern@rowland.harvard.edu \
    --cc=bvanassche@acm.org \
    --cc=cang@codeaurora.org \
    --cc=jejb@linux.ibm.com \
    --cc=kernel@puri.sm \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-scsi@vger.kernel.org \
    --cc=martin.kepplinger@puri.sm \
    --cc=martin.petersen@oracle.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-SCSI Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-scsi/0 linux-scsi/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-scsi linux-scsi/ https://lore.kernel.org/linux-scsi \
		linux-scsi@vger.kernel.org
	public-inbox-index linux-scsi

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-scsi


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git