Re: [PATCH v1] kthread/smpboot: Serialize kthread parking against wakeup

[Kohli, Gaurav]

Corrected the formatting, Sorry for spam.


> HI Peter,
>
> We have tested with new patch and still seeing same issue, in this dumps 
> we don't have debug traces, but seems there still exist race from code 
> review , Can you please check it once:
>
> Controller ThreadÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ CPUHP Thread
> takedown_cpu
> kthread_park
> kthread_parkme
> Set KTHREAD_SHOULD_PARK
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ                        smpboot_thread_fn
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ                        set Task interruptible
>
>
> wake_up_process
>
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ Kthread_parkme
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ SET TASK_PARKED
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ schedule
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ            raw_spin_lock(&rq->lock)
>
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ context_switch
>
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ                        finish_lock_switch
>
>
>
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ Case TASK_PARKED
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ kthread_park_complete
>
>
> SET TASK_INTERRUPTIBLE
>
>
> And also seeing the same warning during unpark of cpuhp from controller:
>  Âif (!wait_task_inactive(p, state)) {
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ WARN_ON(1);
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return;
>  ÂÂÂÂÂÂÂ }
> 325.065893] [<ffffff8920ed0200>] kthread_unpark+0x80/0xd8
> [Â 325.065902] [<ffffff8920eab754>] bringup_cpu+0xa0/0x12c
> [Â 325.065910] [<ffffff8920eaae90>] cpuhp_invoke_callback+0xb4/0x5c8
> [Â 325.065917] [<ffffff8920eabd98>] cpuhp_up_callbacks+0x3c/0x154
> [Â 325.065924] [<ffffff8920ead220>] _cpu_up+0x134/0x208
> [Â 325.065931] [<ffffff8920ead45c>] do_cpu_up+0x168/0x1a0
> [Â 325.065938] [<ffffff8920ead4b8>] cpu_up+0x24/0x30
> [Â 325.065948] [<ffffff89215b1408>] cpu_subsys_online+0x20/0x2c
> [Â 325.065956] [<ffffff89215aac64>] device_online+0x70/0xb4
> [Â 325.065962] [<ffffff89215aad78>] online_store+0xd0/0xdc
> [Â 325.065971] [<ffffff89215a7424>] dev_attr_store+0x40/0x54
> [Â 325.065982] [<ffffff89210d8a98>] sysfs_kf_write+0x5c/0x74
> [Â 325.065988] [<ffffff89210d7b9c>] kernfs_fop_write+0xcc/0x1ec
> [Â 325.065999] [<ffffff8921049288>] vfs_write+0xb4/0x1d0
> [Â 325.066006] [<ffffff892104a858>] SyS_write+0x60/0xc0
> [Â 325.066014] [<ffffff8920e83770>] el0_svc_naked+0x24/0x28
>
>
> And after this same crash occured:
> [Â 325.521307] [<ffffff8920ed4aac>] smpboot_thread_fn+0x26c/0x2c8
> [Â 325.527295] [<ffffff8920ecfb24>] kthread+0xf4/0x108
>
> I will put more debug ftraces to check what is going on exactly.
>
> Regards
> Gaurav

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