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Subject: Re: [PATCH v10 1/2] scsi: ufs: Enable power management for wlun
To:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>
Cc:     Alan Stern <stern@rowland.harvard.edu>,
        Bart Van Assche <bvanassche@acm.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>,
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From:   "Asutosh Das (asd)" <asutoshd@codeaurora.org>
Message-ID: <d9ea43fd-b065-0e6e-07cb-d6ec6ef97bae@codeaurora.org>
Date:   Thu, 18 Mar 2021 10:27:39 -0700
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On 3/18/2021 7:00 AM, Rafael J. Wysocki wrote:
> 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.
> 
Hello,
One approach to address the original issue could be to prevent the scsi 
devices from suspending until the probe is completed, perhaps?

Please let me know if there's a better way to handle this.
Else I'd address all other comments from Adrian and push a change with 
the above approach.

>>          /*
>>           * 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
>>


-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
Linux Foundation Collaborative Project