Messages in this thread | | | Date | Fri, 14 Oct 2022 16:20:53 +0530 | From | Tushar Nimkar <> | Subject | PM-runtime: supplier looses track of consumer during probe |
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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 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. /* 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
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