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From: Saravana Kannan <saravanak@google.com>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	"James E . J . Bottomley" <jejb@linux.ibm.com>,
	"open list:TARGET SUBSYSTEM" <linux-scsi@vger.kernel.org>,
	Avri Altman <avri.altman@wdc.com>, Bean Huo <huobean@gmail.com>,
	Can Guo <cang@codeaurora.org>,
	Asutosh Das <asutoshd@codeaurora.org>,
	Bart Van Assche <bvanassche@acm.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC 2/2] scsi: ufshcd: Fix device links when BOOT WLUN fails to probe
Date: Thu, 8 Jul 2021 09:45:27 -0700	[thread overview]
Message-ID: <CAGETcx_D9KvxEK689ggF6xViiC_yXaCWdL0KoW8uJwiNPhxy8w@mail.gmail.com> (raw)
In-Reply-To: <c3ec3ca2-220f-9e5a-e2ce-b1c2be86c97c@intel.com>

On Thu, Jul 8, 2021 at 7:17 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> On 8/07/21 3:31 pm, Rafael J. Wysocki wrote:
> > On Wed, Jul 7, 2021 at 7:49 PM Adrian Hunter <adrian.hunter@intel.com> wrote:
> >>
> >> On 7/07/21 8:39 pm, Greg Kroah-Hartman wrote:
> >>> On Wed, Jul 07, 2021 at 08:29:48PM +0300, Adrian Hunter wrote:
> >>>> If a LUN fails to probe (e.g. absent BOOT WLUN), the device will not have
> >>>> been registered but can still have a device link holding a reference to the
> >>>> device. The unwanted device link will prevent runtime suspend indefinitely,
> >>>> and cause some warnings if the supplier is ever deleted (e.g. by unbinding
> >>>> the UFS host controller). Fix by explicitly deleting the device link when
> >>>> SCSI destroys the SCSI device.
> >>>>
> >>>> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> >>>> ---
> >>>>  drivers/scsi/ufs/ufshcd.c | 7 +++++++
> >>>>  1 file changed, 7 insertions(+)
> >>>>
> >>>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> >>>> index 708b3b62fc4d..483aa74fe2c8 100644
> >>>> --- a/drivers/scsi/ufs/ufshcd.c
> >>>> +++ b/drivers/scsi/ufs/ufshcd.c
> >>>> @@ -5029,6 +5029,13 @@ static void ufshcd_slave_destroy(struct scsi_device *sdev)
> >>>>              spin_lock_irqsave(hba->host->host_lock, flags);
> >>>>              hba->sdev_ufs_device = NULL;
> >>>>              spin_unlock_irqrestore(hba->host->host_lock, flags);
> >>>> +    } else {
> >>>> +            /*
> >>>> +             * If a LUN fails to probe (e.g. absent BOOT WLUN), the device
> >>>> +             * will not have been registered but can still have a device
> >>>> +             * link holding a reference to the device.
> >>>> +             */
> >>>> +            device_links_scrap(&sdev->sdev_gendev);
> >>>
> >>> What created that link?  And why did it do that before probe happened
> >>> successfully?
> >>
> >> The same driver created the link.
> >>
> >> The documentation seems to say it is allowed to, if it is the consumer.
> >> From Documentation/driver-api/device_link.rst
> >>
> >>   Usage
> >>   =====
> >>
> >>   The earliest point in time when device links can be added is after
> >>   :c:func:`device_add()` has been called for the supplier and
> >>   :c:func:`device_initialize()` has been called for the consumer.
> >
> > Yes, this is allowed, but if you've added device links to a device
> > object that is not going to be registered after all, you are
> > responsible for doing the cleanup.
> >
> > Why can't you call device_link_del() directly on those links?
> >
> > Or device_link_remove() if you don't want to deal with link pointers?
> >
>
> Those only work for DL_FLAG_STATELESS device links, but we use only
> DL_FLAG_PM_RUNTIME | DL_FLAG_RPM_ACTIVE flags.

Is there a reason you can't use DL_FLAG_STATELESS? It doesn't preclude
you from using RPM_ACTIVE as far as I can tell.

-Saravana


-Saravana

  parent reply	other threads:[~2021-07-08 16:46 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-07 17:29 [PATCH RFC 0/2] driver core: Add ability to delete device links of unregistered devices Adrian Hunter
2021-07-07 17:29 ` [PATCH RFC 1/2] " Adrian Hunter
2021-07-07 17:38   ` Greg Kroah-Hartman
2021-07-07 17:29 ` [PATCH RFC 2/2] scsi: ufshcd: Fix device links when BOOT WLUN fails to probe Adrian Hunter
2021-07-07 17:39   ` Greg Kroah-Hartman
2021-07-07 17:49     ` Adrian Hunter
2021-07-08 12:31       ` Rafael J. Wysocki
2021-07-08 14:17         ` Adrian Hunter
2021-07-08 15:03           ` Rafael J. Wysocki
2021-07-08 15:12             ` Rafael J. Wysocki
2021-07-08 16:02               ` Adrian Hunter
2021-07-08 16:45           ` Saravana Kannan [this message]
2021-07-08 16:48             ` Rafael J. Wysocki
2021-07-08 16:57               ` Saravana Kannan
2021-07-08 17:39                 ` Rafael J. Wysocki
2021-07-07 17:40 ` [PATCH RFC 0/2] driver core: Add ability to delete device links of unregistered devices Greg Kroah-Hartman
2021-07-07 17:41   ` Saravana Kannan

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