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In-Reply-To: <24dfb6fc-5d54-6ee2-9195-26428b7ecf8a@intel.com>
From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Thu, 18 Mar 2021 15:00:23 +0100
Message-ID: <CAJZ5v0iOT4oi8Ez5xgN9LE0E7J=_Vb7G8a-9etmu+QTvQ1j9ew@mail.gmail.com>
Subject: Re: [PATCH v10 1/2] scsi: ufs: Enable power management for wlun
To:     Adrian Hunter <adrian.hunter@intel.com>
Cc:     "Asutosh Das (asd)" <asutoshd@codeaurora.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Bart Van Assche <bvanassche@acm.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>, cang@codeaurora.org,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        "open list:TARGET SUBSYSTEM" <linux-scsi@vger.kernel.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Kiwoong Kim <kwmad.kim@samsung.com>,
        Bean Huo <beanhuo@micron.com>,
        Lee Jones <lee.jones@linaro.org>,
        Wei Yongjun <weiyongjun1@huawei.com>,
        Dinghao Liu <dinghao.liu@zju.edu.cn>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Tomas Winkler <tomas.winkler@intel.com>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Satya Tangirala <satyat@google.com>,
        open list <linux-kernel@vger.kernel.org>,
        "moderated list:ARM/SAMSUNG S3C, S5P AND EXYNOS ARM ARCHITECTURES" 
        <linux-arm-kernel@lists.infradead.org>,
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        <linux-samsung-soc@vger.kernel.org>,
        "moderated list:UNIVERSAL FLASH STORAGE HOST CONTROLLER DRIVER..." 
        <linux-mediatek@lists.infradead.org>,
        Linux-PM mailing list <linux-pm@vger.kernel.org>
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On Wed, Mar 17, 2021 at 7:37 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> On 16/03/21 10:35 pm, Asutosh Das (asd) wrote:
> > On 3/16/2021 12:48 AM, Adrian Hunter wrote:
> >> On 16/03/21 12:22 am, Asutosh Das (asd) wrote:
> >>> On 3/14/2021 1:11 AM, Adrian Hunter wrote:
> >>>> On 10/03/21 5:04 am, Asutosh Das (asd) wrote:
> >>>>> On 3/9/2021 7:56 AM, Asutosh Das (asd) wrote:
> >>>>>> On 3/8/2021 9:17 AM, Rafael J. Wysocki wrote:
> >>>>>>> On Mon, Mar 8, 2021 at 5:21 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> >>>>>>>>
> >>>>>>>> On Sat, Mar 6, 2021 at 5:17 PM Alan Stern <stern@rowland.harvard.edu> wrote:
> >>>>>>>>>
> >>>>>>>>> On Fri, Mar 05, 2021 at 06:54:24PM -0800, Asutosh Das (asd) wrote:
> >>>>>>>>>
> >>>>>>>>>> Now during my testing I see a weird issue sometimes (1 in 7).
> >>>>>>>>>> Scenario - bootups
> >>>>>>>>>>
> >>>>>>>>>> Issue:
> >>>>>>>>>> The supplier 'ufs_device_wlun 0:0:0:49488' goes into runtime suspend even
> >>>>>>>>>> when one/more of its consumers are in RPM_ACTIVE state.
> >>>>>>>>>>
> >>>>>>>>>> *Log:
> >>>>>>>>>> [   10.056379][  T206] sd 0:0:0:1: [sdb] Synchronizing SCSI cache
> >>>>>>>>>> [   10.062497][  T113] sd 0:0:0:5: [sdf] Synchronizing SCSI cache
> >>>>>>>>>> [   10.356600][   T32] sd 0:0:0:7: [sdh] Synchronizing SCSI cache
> >>>>>>>>>> [   10.362944][  T174] sd 0:0:0:3: [sdd] Synchronizing SCSI cache
> >>>>>>>>>> [   10.696627][   T83] sd 0:0:0:2: [sdc] Synchronizing SCSI cache
> >>>>>>>>>> [   10.704562][  T170] sd 0:0:0:6: [sdg] Synchronizing SCSI cache
> >>>>>>>>>> [   10.980602][    T5] sd 0:0:0:0: [sda] Synchronizing SCSI cache
> >>>>>>>>>>
> >>>>>>>>>> /** Printing all the consumer nodes of supplier **/
> >>>>>>>>>> [   10.987327][    T5] ufs_device_wlun 0:0:0:49488: usage-count @ suspend: 0
> >>>>>>>>>> <-- this is the usage_count
> >>>>>>>>>> [   10.994440][    T5] ufs_rpmb_wlun 0:0:0:49476: PM state - 2
> >>>>>>>>>> [   11.000402][    T5] scsi 0:0:0:49456: PM state - 2
> >>>>>>>>>> [   11.005453][    T5] sd 0:0:0:0: PM state - 2
> >>>>>>>>>> [   11.009958][    T5] sd 0:0:0:1: PM state - 2
> >>>>>>>>>> [   11.014469][    T5] sd 0:0:0:2: PM state - 2
> >>>>>>>>>> [   11.019072][    T5] sd 0:0:0:3: PM state - 2
> >>>>>>>>>> [   11.023595][    T5] sd 0:0:0:4: PM state - 0 << RPM_ACTIVE
> >>>>>>>>>> [   11.353298][    T5] sd 0:0:0:5: PM state - 2
> >>>>>>>>>> [   11.357726][    T5] sd 0:0:0:6: PM state - 2
> >>>>>>>>>> [   11.362155][    T5] sd 0:0:0:7: PM state - 2
> >>>>>>>>>> [   11.366584][    T5] ufshcd-qcom 1d84000.ufshc: __ufshcd_wl_suspend - 8709
> >>>>>>>>>> [   11.374366][    T5] ufs_device_wlun 0:0:0:49488: __ufshcd_wl_suspend -
> >>>>>>>>>> (0) has rpm_active flags
> >>>>>>>>
> >>>>>>>> Do you mean that rpm_active of the link between the consumer and the
> >>>>>>>> supplier is greater than 0 at this point and the consumer is
> >>>>>>>
> >>>>>>> I mean is rpm_active of the link greater than 1 (because 1 means "no
> >>>>>>> active references to the supplier")?
> >>>>>> Hi Rafael:
> >>>>>> No - it is not greater than 1.
> >>>>>>
> >>>>>> I'm trying to understand what's going on in it; will update when I've something.
> >>>>>>
> >>>>>>>
> >>>>>>>> RPM_ACTIVE, but the supplier suspends successfully nevertheless?
> >>>>>>>>
> >>>>>>>>>> [   11.383376][    T5] ufs_device_wlun 0:0:0:49488:
> >>>>>>>>>> ufshcd_wl_runtime_suspend <-- Supplier suspends fine.
> >>>>>>>>>> [   12.977318][  T174] sd 0:0:0:4: [sde] Synchronizing SCSI cache
> >>>>>>>>>>
> >>>>>>>>>> And the the suspend of sde is stuck now:
> >>>>>>>>>> schedule+0x9c/0xe0
> >>>>>>>>>> schedule_timeout+0x40/0x128
> >>>>>>>>>> io_schedule_timeout+0x44/0x68
> >>>>>>>>>> wait_for_common_io+0x7c/0x100
> >>>>>>>>>> wait_for_completion_io+0x14/0x20
> >>>>>>>>>> blk_execute_rq+0x90/0xcc
> >>>>>>>>>> __scsi_execute+0x104/0x1c4
> >>>>>>>>>> sd_sync_cache+0xf8/0x2a0
> >>>>>>>>>> sd_suspend_common+0x74/0x11c
> >>>>>>>>>> sd_suspend_runtime+0x14/0x20
> >>>>>>>>>> scsi_runtime_suspend+0x64/0x94
> >>>>>>>>>> __rpm_callback+0x80/0x2a4
> >>>>>>>>>> rpm_suspend+0x308/0x614
> >>>>>>>>>> pm_runtime_work+0x98/0xa8
> >>>>>>>>>>
> >>>>>>>>>> I added 'DL_FLAG_RPM_ACTIVE' while creating links.
> >>>>>>>>>>          if (hba->sdev_ufs_device) {
> >>>>>>>>>>                  link = device_link_add(&sdev->sdev_gendev,
> >>>>>>>>>>                                      &hba->sdev_ufs_device->sdev_gendev,
> >>>>>>>>>>                                     DL_FLAG_PM_RUNTIME|DL_FLAG_RPM_ACTIVE);
> >>>>>>>>>> I didn't expect this to resolve the issue anyway and it didn't.
> >>>>>>>>>>
> >>>>>>>>>> Another interesting point here is when I resume any of the above suspended
> >>>>>>>>>> consumers, it all goes back to normal, which is kind of expected. I tried
> >>>>>>>>>> resuming the consumer and the supplier is resumed and the supplier is
> >>>>>>>>>> suspended when all the consumers are suspended.
> >>>>>>>>>>
> >>>>>>>>>> Any pointers on this issue please?
> >>>>>>>>>>
> >>>>>>>>>> @Bart/@Alan - Do you've any pointers please?
> >>>>>>>>>
> >>>>>>>>> It's very noticeable that although you seem to have isolated a bug in
> >>>>>>>>> the power management subsystem (supplier goes into runtime suspend
> >>>>>>>>> even when one of its consumers is still active), you did not CC the
> >>>>>>>>> power management maintainer or mailing list.
> >>>>>>>>>
> >>>>>>>>> I have added the appropriate CC's.
> >>>>>>>>
> >>>>>>>> Thanks Alan!
> >>>>>>
> >>>>>>
> >>>>>
> >>>>> Hello
> >>>>> I & Can (thanks CanG) debugged this further:
> >>>>>
> >>>>> Looks like this issue can occur if the sd probe is asynchronous.
> >>>>>
> >>>>> Essentially, the sd_probe() is done asynchronously and driver_probe_device() invokes pm_runtime_get_suppliers() before invoking sd_probe().
> >>>>>
> >>>>> But scsi_probe_and_add_lun() runs in a separate context.
> >>>>> So the scsi_autopm_put_device() invoked from scsi_scan_host() context reduces the link->rpm_active to 1. And sd_probe() invokes scsi_autopm_put_device() and starts a timer. And then driver_probe_device() invoked from __device_attach_async_helper context reduces the link->rpm_active to 1 thus enabling the supplier to suspend before the consumer suspends.
> >>>>>
> >>>>> So if:
> >>>>> Context T1:
> >>>>> [1] scsi_probe_and_add_lun()
> >>>>> [2]    |- scsi_autopm_put_device() - reduce the link->rpm_active to 1
> >>>>>
> >>>>> Context T2:
> >>>>> __device_attach_async_helper()
> >>>>>       |- driver_probe_device()
> >>>>>           |- sd_probe()
> >>>>> In between [1] and [2] say, driver_probe_device() -> sd_probe() is invoked in a separate context from __device_attach_async_helper().
> >>>>> The driver_probe_device() -> pm_runtime_get_suppliers() but [2] would reduce link->rpm_active to 1.
> >>>>> Then sd_probe() would invoke rpm_resume() and proceed as is.
> >>>>> When sd_probe() invokes scsi_autopm_put_device() it'd start a timer, dev->power.timer_autosuspends = 1.
> >>>>>
> >>>>> Now then, pm_runtime_put_suppliers() is invoked from driver_probe_device() and that makes the link->rpm_active = 1.
> >>>>> But by now, the corresponding 'sd dev' (consumer) usage_count = 0, state = RPM_ACTIVE and link->rpm_active = 1.
> >>>>> At this point of time, all other 'sd dev' (consumers) _may_ be suspended or active but would have the link->rpm_active = 1.
> >>>>
> >>>> Is this with DL_FLAG_RPM_ACTIVE?  In that case, wouldn't active
> >>>> consumers have link->rpm_active = 2 and also have incremented
> >>>> the supplier's usage_count?
> >
> > Yes this is with DL_FLAG_RPM_ACTIVE.
> >
> > Please let me share a log here:
> > BEF means - Before, AFT means After.
> >
> > [    6.843445][    T7] scsi 0:0:0:4: [UFSDBG]: ufshcd_setup_links:4779:  supp: usage_cnt: 3 Link - 0:0:0:49488 link-rpm_active: 2 avail_luns: 5
> > [    6.892545][    T7] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
> >
> > In the above log, T7 is the context in which this scsi device is being added - scsi_sysfs_add_sdev()
> >
> > [    6.931846][    T7] ufs_rpmb_wlun 0:0:0:4: [UFSDBG]: ufshcd_rpmb_probe:9692: invoked
> > [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 4
> >
> > [    6.941246][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 5
> > [    6.941247][    T7] scsi 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 4 rpm_active: 3
> >
> > [    6.941267][    T7] scsi 0:0:0:4: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 4 rpm_active: 3
> >
> > ------ T196 Context comes in while T7 is running ----------
> > [    6.941466][  T196] scsi 0:0:0:4: pm_runtime_get_suppliers: (0:0:0:49488): supp: usage_count: 5 rpm_active: 4
> > --------------------------------------------------------------
> >
> > [    7.788397][    T7] scsi 0:0:0:4: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 2 rpm_active: 1
>
>
>
> >
> > --
> >
> > T196 is the context in which sd_probe() is invoked for this scsi device.
> >
> > [    7.974410][  T196] sd 0:0:0:4: [sde] Attached SCSI disk
> > [    7.984188][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: rpm_active: 2
> > [    7.998424][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [BEF] usage_count: 4
> > [    8.017320][  T196] sd 0:0:0:4: pm_runtime_put_suppliers: (0:0:0:49488) [AFT] usage_count: 1 rpm_active: 1
> >
> > The reference to the link is released after sd_probe() is completed.
> > At this point, the rpm_active should be 2. And the rpm_active should become 1 when sd 0:0:0:4 actually suspends. But at the end of sd_probe() the suspend is only scheduled. However the supplier is now free to suspend.
> >
> > In this log, the usage_count of supplier becomes 0 here:
> > [   11.963885][  T117] sd 0:0:0:7: rpm_put_suppliers: [BEF] Supp (0:0:0:49488) usage_count: 1 rpm_active: 2
> > [   11.973821][  T117] sd 0:0:0:7: rpm_put_suppliers: [AFT] Supp (0:0:0:49488) usage_count: 0 rpm_active: 1
> >
> > However, the consumer sd 0:0:0:4 is still active but has released the reference to the supplier:
>
> If that is the case, then it is an error in PM not UFS.
>
> A second look at the code around rpm_put_suppliers() does look
> potentially racy, since there does not appear to be anything
> stopping the runtime_status changing between
> spin_unlock_irq(&dev->power.lock) and device_links_read_lock().
>
> Rafael, can you comment?

Indeed, if the device is suspending, changing its PM-runtime status to
RPM_SUSPENDED and dropping its power.lock allows a concurrent
rpm_resume() to run and resume the device before the suppliers can be
suspended.

That's incorrect and has been introduced by commit 44cc89f76464 ("PM:
runtime: Update device status before letting suppliers suspend").

It is probably better to revert that commit and address the original
issue in a different way.

>         /*
>          * If the device is suspending and the callback has returned success,
>          * drop the usage counters of the suppliers that have been reference
>          * counted on its resume.
>          *
>          * Do that if the resume fails too.
>          */
>         put = dev->power.runtime_status == RPM_SUSPENDING && !retval;
>         if (put)
>                 __update_runtime_status(dev, RPM_SUSPENDED);
>         else
>                 put = get && retval;
>
>         if (put) {
>                 spin_unlock_irq(&dev->power.lock);
>
>                 idx = device_links_read_lock();
>
> fail:
>                 rpm_put_suppliers(dev);
>
>                 device_links_read_unlock(idx);
>
>                 spin_lock_irq(&dev->power.lock);
>         }
>
>
>
>
> > [   12.002792][  T117] scsi 0:0:0:49456: rpm_status - 2
> > [   12.002806][  T117] sd 0:0:0:0: rpm_status - 2
> > [   12.002834][  T117] sd 0:0:0:1: rpm_status - 2
> > [   12.017730][  T117] sd 0:0:0:2: rpm_status - 2
> > [   12.041317][  T117] sd 0:0:0:3: rpm_status - 2
> > [   12.045953][  T117] sd 0:0:0:4: rpm_status - 0
> >
> > And sd 0:0:0:4 tries to suspend here:
> > [   15.465914][  T117] sd 0:0:0:4: [sde] Synchronizing SCSI cache
> >
> >>>>
> >>>> Another outstanding issue that comes to mind, is to ensure
> >>>> hba->sdev_ufs_device does not runtime suspend before it is probed.
> >>>> I suggest changing ufshcd_slave_configure() so it does not set
> >>>> sdev->rpm_autosuspend for hba->sdev_ufs_device, and instead do
> >>>> pm_runtime_allow / pm_runtime_forbid() in ufshcd_wl_probe() /
> >>>> ufshcd_wl_remove() respectively.
> >>>>
> > If pm_runtime_allow() is invoked from ufshcd_wl_probe() it'd invoke runtime_suspend on hba->sdev_ufs_device before exiting scsi_sysfs_add_sdev(). So I think pm_runtime_allow() should be invoked in ufshcd_scsi_add_wlus().
> >
> >>>> However we still want to stop hba->sdev_ufs_device runtime
> >>>> suspending while consumers are being added.  With that in mind,
> >>>> I would expect pm_runtime_get_noresume(&hba->sdev_ufs_device->sdev_gendev)
> >>>> in ufshcd_scsi_add_wlus() to come *before*
> >>>> ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).  In fact, it would
> >>>> be more logical to make it, pm_runtime_get_sync() since we require
> >>>> hba->sdev_ufs_device to be active at that point.
> >>>>
> > Correct, scsi_autopm_get_device(hba->sdev_ufs_device) should be invoked before ufshcd_blk_pm_runtime_init(hba->sdev_ufs_device).
> > Now a corresponding scsi_autopm_put_device(hba->sdev_ufs_device) is invoked after the consumers are added in ufshcd_setup_links().
> > Even then I think this issue would still pop up.
> >
> >>>>
> >>>
> >>> Hi Adrian,
> >>> I think the v11 that I pushed can handle this.
> >>> runtime-suspend is forbidden at probe and is re-enabled after probe is done. Please take a look and let me know if I'm missing something.
> >>
> >> If the PM APIs are being used correctly, the usage and active
> >> counts should never be wrong.  If they were, then that would
> >> be an issue for the PM framework.
> >> It is more likely that I'm using it incorrectly :).
> >
> >> However, it is hard to tell what the issues are until all the
> >> UFS driver changes have been completed, such as the ones I
> >> suggested above above.
> >>
> > Ok, understood.
> >
> >> v11 could be hiding issues rather than fixing them.
> >>
> > Based on the logs, in v11, I tried to forbid any runtime-suspend until sd_probe() is done.
> > I could be misunderstanding the whole thing though.
> >
> > Having said that, I will make the changes as per your suggestions and push a v12. I will test with v12 as well and see if this issue is seen.
> >
> >>>
> >>>>>
> >>>>> Since the supplier has 0 auto-suspend delay, it now suspends!
> >>>>>
> >>>>>
> >>>>> Context [T1]
> >>>>> Call trace:
> >>>>> dump_backtrace+0x0/0x1d4
> >>>>> show_stack+0x18/0x24
> >>>>> dump_stack+0xc4/0x144
> >>>>> __pm_runtime_idle+0xb4/0x184
> >>>>> scsi_autopm_put_device+0x18/0x24
> >>>>> scsi_sysfs_add_sdev+0x26c/0x278
> >>>>> scsi_probe_and_add_lun+0xbac/0xd48
> >>>>> __scsi_scan_target+0x38c/0x510
> >>>>> scsi_scan_host_selected+0x14c/0x1e4
> >>>>> scsi_scan_host+0x1e0/0x228
> >>>>> ufshcd_async_scan+0x39c/0x408
> >>>>> async_run_entry_fn+0x48/0x128
> >>>>> process_one_work+0x1f0/0x470
> >>>>> worker_thread+0x26c/0x4c8
> >>>>> kthread+0x13c/0x320
> >>>>> ret_from_fork+0x10/0x18
> >>>>>
> >>>>>
> >>>>> Context [T2]
> >>>>> Call trace:
> >>>>> dump_backtrace+0x0/0x1d4
> >>>>> show_stack+0x18/0x24
> >>>>> dump_stack+0xc4/0x144
> >>>>> rpm_get_suppliers+0x48/0x1ac
> >>>>> __rpm_callback+0x58/0x12c
> >>>>> rpm_resume+0x3a4/0x618
> >>>>> __pm_runtime_resume+0x50/0x80
> >>>>> scsi_autopm_get_device+0x20/0x54
> >>>>> sd_probe+0x40/0x3d0
> >>>>> really_probe+0x1bc/0x4a0
> >>>>> driver_probe_device+0x84/0xf0
> >>>>> __device_attach_driver+0x114/0x138
> >>>>> bus_for_each_drv+0x84/0xd0
> >>>>> __device_attach_async_helper+0x7c/0xf0
> >>>>> async_run_entry_fn+0x48/0x128
> >>>>> process_one_work+0x1f0/0x470
> >>>>> worker_thread+0x26c/0x4c8
> >>>>> kthread+0x13c/0x320
> >>>>> ret_from_fork+0x10/0x18
> >>>>>
> >>>>> Below prints show how link->rpm_active becomes 1 for sd 0:0:0:4
> >>>>> [    7.574654][  T212] Call trace:
> >>>>> [    7.574657][  T212]  dump_backtrace+0x0/0x1d4
> >>>>> [    7.574661][  T212]  show_stack+0x18/0x24
> >>>>> [    7.574665][  T212]  dump_stack+0xc4/0x144
> >>>>> [    7.574668][  T212]  __pm_runtime_idle+0xb4/0x184
> >>>>> [    7.574671][  T212]  scsi_autopm_put_device+0x18/0x24
> >>>>> [    7.574675][  T212]  sd_probe+0x314/0x3d0
> >>>>> [    7.574677][  T212]  really_probe+0x1bc/0x4a0
> >>>>> [    7.574680][  T212]  driver_probe_device+0x84/0xf0
> >>>>> [    7.574683][  T212]  __device_attach_driver+0x114/0x138
> >>>>> [    7.574686][  T212]  bus_for_each_drv+0x84/0xd0
> >>>>> [    7.574689][  T212]  __device_attach_async_helper+0x7c/0xf0
> >>>>> [    7.574692][  T212]  async_run_entry_fn+0x48/0x128
> >>>>> [    7.574695][  T212]  process_one_work+0x1f0/0x470
> >>>>> [    7.574698][  T212]  worker_thread+0x26c/0x4c8
> >>>>> [    7.574700][  T212]  kthread+0x13c/0x320
> >>>>> [    7.574703][  T212]  ret_from_fork+0x10/0x18
> >>>>> [    7.574706][  T212] sd 0:0:0:4: scsi_runtime_idle
> >>>>> [    7.574712][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: -16 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
> >>>>> [    7.574715][  T212] sd 0:0:0:4: sd_probe: [UFSDBG]: Exit
> >>>>> [    7.574738][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
> >>>>>
> >>>>> [    7.574752][  T212] Workqueue: events_unbound async_run_entry_fn
> >>>>> [    7.574754][  T212] Call trace:
> >>>>> [    7.574758][  T212]  dump_backtrace+0x0/0x1d4
> >>>>> [    7.574761][  T212]  show_stack+0x18/0x24
> >>>>> [    7.574765][  T212]  dump_stack+0xc4/0x144
> >>>>> [    7.574767][  T212]  __pm_runtime_idle+0xb4/0x184
> >>>>> [    7.574770][  T212]  driver_probe_device+0x94/0xf0
> >>>>> [    7.574773][  T212]  __device_attach_driver+0x114/0x138
> >>>>> [    7.574775][  T212]  bus_for_each_drv+0x84/0xd0
> >>>>> [    7.574778][  T212]  __device_attach_async_helper+0x7c/0xf0
> >>>>> [    7.574781][  T212]  async_run_entry_fn+0x48/0x128
> >>>>> [    7.574783][  T212]  process_one_work+0x1f0/0x470
> >>>>> [    7.574786][  T212]  worker_thread+0x26c/0x4c8
> >>>>> [    7.574788][  T212]  kthread+0x13c/0x320
> >>>>> [    7.574791][  T212]  ret_from_fork+0x10/0x18
> >>>>> [    7.574848][   T80] sd 0:0:0:4: scsi_runtime_idle
> >>>>> [    7.574858][  T212] sd 0:0:0:4: __pm_runtime_idle: aft: [UFSDBG]: pwr.timer_autosuspends: 1 pwr.request_pending: 0 retval: 0 pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:2
> >>>>> [    7.574863][  T212] sd 0:0:0:4: pm_runtime_put_suppliers: [UFSDBG]: rpm_status: 0 link-rpm_active:1
> >>>>> [    7.574866][  T212] sd 0:0:0:4: async probe completed
> >>>>> [    7.574870][  T212] sd 0:0:0:4: __pm_runtime_idle: b4: [UFSDBG]: pwr.request: 0 usage_count: 0 rpm_status: 0 link-rpm_active:1
> >>>>>
> >>>>>
> >>>>> So, from the above it looks like when async probe is enabled this is a possibility.
> >>>>>
> >>>>> I don't see a way around this. Please let me know if you (@Alan/@Bart/@Adrian) have any thoughts on this.
> >>>>>
> >>>>> Thanks,
> >>>>> -asd
> >>>>>
> >>>>
> >>>
> >>>
> >>
> >
> >
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> > Linux Foundation Collaborative Project
>