Linux-SCSI Archive on lore.kernel.org
 help / color / Atom feed
From: Martin Kepplinger <martin.kepplinger@puri.sm>
To: Alan Stern <stern@rowland.harvard.edu>,
	Bart Van Assche <bvanassche@acm.org>
Cc: 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: Mon, 29 Jun 2020 11:42:59 +0200
Message-ID: <c19f1938-ae47-2357-669d-5b4021aec154@puri.sm> (raw)
In-Reply-To: <20200626154441.GA296771@rowland.harvard.edu>



On 26.06.20 17:44, Alan Stern wrote:
> On Fri, Jun 26, 2020 at 08:07:51AM -0700, Bart Van Assche wrote:
>> On 2020-06-25 01:16, Martin Kepplinger wrote:
>>> here's roughly what happens when enabling runtime PM in sysfs (again,
>>> because sd_probe() calls autopm_put() and thus allows it:
>>>
>>> [   27.384446] sd 0:0:0:0: scsi_runtime_suspend
>>> [   27.432282] blk_pre_runtime_suspend
>>> [   27.435783] sd_suspend_common
>>> [   27.438782] blk_post_runtime_suspend
>>> [   27.442427] scsi target0:0:0: scsi_runtime_suspend
>>> [   27.447303] scsi host0: scsi_runtime_suspend
>>>
>>> then I "mount /dev/sda1 /mnt" and none of the resume() functions get
>>> called. To me it looks like the sd driver should initiate resuming, and
>>> that's not implemented.
>>>
>>> what am I doing wrong or overlooking? how exactly does (or should) the
>>> block layer initiate resume here?
>>
>> As far as I know runtime power management support in the sd driver is working
>> fine and is being used intensively by the UFS driver. The following commit was
>> submitted to fix a bug encountered by an UFS developer: 05d18ae1cc8a ("scsi:
>> pm: Balance pm_only counter of request queue during system resume") # v5.7.
> 
> I just looked at that commit for the first time.
> 
> Instead of making the SCSI driver do the work of deciding what routine to 
> call, why not redefine blk_set_runtime_active(q) to simply call 
> blk_post_runtime_resume(q, 0)?  Or vice versa: if err == 0 have 
> blk_post_runtime_resume call blk_set_runtime_active?
> 
> After all, the two routines do almost the same thing -- and the bug 
> addressed by this commit was caused by the difference in their behaviors.
> 
> If the device was already runtime-active during the system suspend, doing 
> an extra clear of the pm_only counter won't hurt anything.
> 
>> I'm not sure which bug is causing trouble on your setup but I think it's likely
>> that the root cause is somewhere else than in the block layer, the SCSI core
>> or the SCSI sd driver.
>>
>> Bart.
> 
> 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".

thanks,
                                martin

  parent reply index

Thread overview: 56+ 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 [this message]
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
2020-07-29 15:40                                       ` 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

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=c19f1938-ae47-2357-669d-5b4021aec154@puri.sm \
    --to=martin.kepplinger@puri.sm \
    --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.petersen@oracle.com \
    --cc=stern@rowland.harvard.edu \
    /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