On 4/11/22 11:19, Tushar Nimkar wrote: > Hi linux-pm/linux-scsi, > > Gentle reminder! > > Can you please provide your suggestions on below race? > > Thanks, Tushar Nimkar > > On 10/14/2022 4:20 PM, Tushar Nimkar wrote: >> Hi linux-pm/linux-scsi, >> >> We have included fix [1] but continuing to observe supplier loosing track of consumer. >> >> Below is trace snippet with additional logging added. >> Here consumer is 0:0:0:0 and supplier is 0:0:0:49488. In Last three lines consumer resume is completed but supplier is put down. >> >> kworker/u16:0-7 0.880014: rpm_idle: 0:0:0:0 flags-4 cnt-0 dep-0 auto-1 p-0 irq-0 child-0 >> kworker/u16:0-7 0.880017: bprint: pm_runtime_mark_last_busy.46700: :#205 dev_name:0:0:0:0 ktime_get_mono_fast_ns():852365364 >> kworker/u16:0-7 0.880019: rpm_suspend: 0:0:0:0 flags-8 cnt-0 dep-0 auto-1 p-0 irq-0 child-0 >> kworker/u16:0-7 0.880022: bprint: pm_runtime_put_noidle.44083: pm_runtime_put_noidle: #112 dev_name:0:0:0:49488 dev usage_count:5 decremented usage count >> kworker/u16:0-7 0.880023: bprint: pm_runtime_put_noidle.44083: pm_runtime_put_noidle: #112 dev_name:0:0:0:49488 dev usage_count:4 decremented usage count >> kworker/u16:2-142 0.880024: rpm_resume: 0:0:0:0 flags-4 cnt-1 dep-0 auto-1 p-0 irq-0 child-0 >> kworker/u16:0-7 0.880025: bprint: __rpm_put_suppliers: __rpm_put_suppliers: #348 consumer:0:0:0:0 supplier:0:0:0:49488 usage_count:4 >> kworker/u16:0-7 0.880061: rpm_idle: 0:0:0:49488 flags-1 cnt-4 dep-0 auto-1 p-0 irq-0 child-0 >> kworker/u16:0-7 0.880062: rpm_return_int: rpm_idle+0x16c:0:0:0:49488 ret=-11 >> kworker/u16:2-142 0.880062: bprint: __pm_runtime_resume: __pm_runtime_resume: #1147 dev_name:0:0:0:49488 dev usage_count:5 incremented usage count >> kworker/u16:2-142 0.880063: rpm_resume: 0:0:0:49488 flags-4 cnt-5 dep-0 auto-1 p-0 irq-0 child-0 >> kworker/u16:2-142 0.880063: rpm_return_int: rpm_resume+0x690:0:0:0:49488 ret=1 >> kworker/u16:0-7 0.880063: rpm_return_int: rpm_suspend+0x68:0:0:0:0 ret=0 >> kworker/u16:2-142 0.880063: bprint: rpm_get_suppliers: rpm_get_suppliers: #300 consumer:0:0:0:0 supplier:0:0:0:49488 usage_count:5 >> kworker/u16:0-7 0.880065: bprint: pm_runtime_put_noidle.44083: pm_runtime_put_noidle: #112 dev_name:0:0:0:49488 dev usage_count:4 decremented usage count >> kworker/u16:2-142 0.880065: bprint: pm_runtime_mark_last_busy.44088: :#205 dev_name:0:0:0:0 ktime_get_mono_fast_ns():852413749 >> kworker/u16:2-142 0.880065: rpm_idle: 0:0:0:0 flags-1 cnt-1 dep-0 auto-1 p-0 irq-0 child-0 >> kworker/u16:2-142 0.880065: rpm_return_int: rpm_idle+0x16c:0:0:0:0 ret=-11 >> kworker/u16:0-7 0.880066: bprint: __rpm_put_suppliers: __rpm_put_suppliers: #348 consumer:0:0:0:0 supplier:0:0:0:49488 usage_count:4 >> kworker/u16:0-7 0.880067: rpm_return_int: rpm_idle+0x16c:0:0:0:0 ret=-16 >> kworker/u16:2-142 0.880067: rpm_return_int: rpm_resume+0x690:0:0:0:0 ret=0 >> >> Upon looking into this further the race looks to be in below two processes running in parallel and process-1 is putting down supplier at [C] because process-2 is setting runtime_status as resuming at [D]. >> >> Also as per runtime PM documentation >> In order to use autosuspend, subsystems or drivers must call >> pm_runtime_use_autosuspend(), and thereafter they should use the various `*_autosuspend()` helper functions... >> >> It was also observed that *_autosuspend() API at point [A] was invoked without first invoking pm_runtime_use_autosuspend() which return expiration as zero at point [B] and proceeds ahead for immediate runtime suspend of device which seems lead to this race condition. >> >> Process -1 >> ufshcd_async_scan context (process 1) >> scsi_autopm_put_device() //0:0:0:0 I am having trouble following your description. What function is calling scsi_autopm_put_device() here? >> pm_runtime_put_sync() >> __pm_runtime_idle() >> rpm_idle() -- RPM_GET_PUT(4) >> __rpm_callback >> scsi_runtime_idle() >> pm_runtime_mark_last_busy() >> pm_runtime_autosuspend() --[A] >> rpm_suspend() -- RPM_AUTO(8) >> pm_runtime_autosuspend_expiration() use_autosuspend is false return 0 --- [B] >> __update_runtime_status to RPM_SUSPENDING >> __rpm_callback() >> __rpm_put_suppliers(dev, false) >> __update_runtime_status to RPM_SUSPENDED >> rpm_suspend_suppliers() >> rpm_idle() for supplier -- RPM_ASYNC(1) return (-EAGAIN) [ Other consumer active for supplier] >> rpm_suspend() – END with return=0 >> scsi_runtime_idle() END return (-EBUSY) always. Not following here either. Which device is EBUSY and why? >> /* Do that if resume fails too.*/ >> (dev->power.runtime_status == RPM_RESUMING && retval))) return -EBUSY >> __rpm_put_suppliers(dev, false) -- [C] >> rpm_idle() END return -EBUSY >> >> Process -2 >> sd_probe context (Process 2) >> scsi_autopm_get_device() //0:0:0:0 >> __pm_runtime_resume(RPM_GET_PUT) >> rpm_resume() -- RPM_GET_PUT(4) >> __update_runtime_status to RPM_RESUMING --[D] >> __rpm_callback() >> rpm_get_suppliers() >> __pm_runtime_resume() - RPM_GET_PUT(4) – supplier >> rpm_resume() for supplier. >> __update_runtime_status to RPM_ACTIVE >> pm_runtime_mark_last_busy () >> rpm_resume() END return 0 >> >> Can you please provide your suggestions on addressing above race condition? >> >> This is also reported at [2]. >> >> [1]: https://lore.kernel.org/lkml/4748074.GXAFRqVoOG@kreacher/T/ >> [2]: https://lkml.org/lkml/2022/10/12/259 >> >> Thanks, >> Tushar Nimkar
