Messages in this thread | | | Subject | Re: [PATCH v10 1/2] scsi: ufs: Enable power management for wlun | From | "Asutosh Das (asd)" <> | Date | Thu, 18 Mar 2021 10:58:19 -0700 |
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On 3/18/2021 10:54 AM, Rafael J. Wysocki wrote: > On Thu, Mar 18, 2021 at 6:33 PM Asutosh Das (asd) > <asutoshd@codeaurora.org> wrote: >> >> 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? > > I was talking about the original issue that commit 44cc89f76464 > attempted to address. > > I'm not sure if and how it is related to the issue you have been debugging. > Hi Rafael Thanks for clarifying that. Understood. I was referring to the issue that I've been discussing with Adrian.
-asd
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