Re: [PATCH v20 1/2] scsi: ufs: Enable power management for wlun

[Adrian Hunter]

On 22/04/21 7:38 pm, Asutosh Das (asd) wrote:
> On 4/20/2021 12:42 AM, Adrian Hunter wrote:
>> On 20/04/21 7:15 am, Adrian Hunter wrote:
>>> On 20/04/21 12:53 am, Asutosh Das (asd) wrote:
>>>> On 4/19/2021 11:37 AM, Adrian Hunter wrote:
>>>>> On 16/04/21 10:49 pm, Asutosh Das wrote:
>>>>>>
>>>>>> Co-developed-by: Can Guo <cang@xxxxxxxxxxxxxx>
>>>>>> Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
>>>>>> Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
>>>>>> ---
>>>>>
>>>>> I came across 3 issues while testing.  See comments below.
>>>>>
>>>> Hi Adrian
>>>> Thanks for the comments.
>>>>> <SNIP>
>>>>>
>>>>>> @@ -5794,7 +5839,7 @@ static void ufshcd_err_handling_unprepare(struct ufs_hba *hba)
>>>>>>        if (ufshcd_is_clkscaling_supported(hba))
>>>>>>            ufshcd_clk_scaling_suspend(hba, false);
>>>>>>        ufshcd_clear_ua_wluns(hba);
>>>>>
>>>>> ufshcd_clear_ua_wluns() deadlocks trying to clear UFS_UPIU_RPMB_WLUN
>>>>> if sdev_rpmb is suspended and sdev_ufs_device is suspending.
>>>>> e.g. ufshcd_wl_suspend() is waiting on host_sem while ufshcd_err_handler()
>>>>> is running, at which point sdev_rpmb has already suspended.
>>>>>
>>>> Umm, I didn't understand this deadlock.
>>>> When you say, sdev_rpmb is suspended, does it mean runtime_suspended?
>>>> sdev_ufs_device is suspending - this can't be runtime_suspending, while ufshcd_err_handling_unprepare is running.
>>>>
>>>> If you've a call-stack of this deadlock, please can you share it with me. I'll also try to reproduce this.
>>>
>>> Yes it is system suspend. sdev_rpmb has suspended, sdev_ufs_device is waiting on host_sem.
>>> ufshcd_err_handler() holds host_sem. ufshcd_clear_ua_wlun(UFS_UPIU_RPMB_WLUN) gets stuck.
>>> I will get some call-stacks.
>>
> Hi Adrian,
> 
> Thanks for the call stacks.
> From the current information, I can't say for sure why it'd get stuck in blk_queue_enter().

I presume SCSI is leaving the RPMB WLUN device runtime suspended and consequently the queue status is RPM_SUSPENDED

> 
> I tried reproducing this issue on my setup yesterday but couldn't.
> Here's what I did:
> 1. sdev_rpmb is RPM_SUSPENDED, checked before initiating system suspend
> 2. sdev_ufs_device is RPM_RESUMED
> 3. I triggered system suspend (echo mem > /sys/power/state) and scheduled the error handler from ufshcd_wl_suspend().
> 4. Waited until error handler ran and then ufshcd_wl_suspend() blocks on host_sem.
> 5. The ufshcd_clear_wa_wlun(UFS_UPIU_RPMB_WLUN) went through fine.
> 
> Do you've some specific steps to reproduce this or a script, perhaps? If so, please can you share it with me. I will try again.

I was using a device that gives occasional errors, but I will what see I can do.

> My test environment is in 5.10 kernel with Android, I suppose that should be ok though.
> 
> Thanks
> -asd
> 
>> Here are the call stacks
>>
>> [   34.094321] Workqueue: ufs_eh_wq_0 ufshcd_err_handler
>> [   34.094788] Call Trace:
>> [   34.095281]  __schedule+0x275/0x6c0
>> [   34.095743]  schedule+0x41/0xa0
>> [   34.096240]  blk_queue_enter+0x10d/0x230
>> [   34.096693]  ? wait_woken+0x70/0x70
>> [   34.097167]  blk_mq_alloc_request+0x53/0xc0
>> [   34.097610]  blk_get_request+0x1e/0x60
>> [   34.098053]  __scsi_execute+0x3c/0x260
>> [   34.098529]  ufshcd_clear_ua_wlun.cold+0xa6/0x14b
>> [   34.098977]  ufshcd_clear_ua_wluns.part.0+0x4d/0x92
>> [   34.099456]  ufshcd_err_handler+0x97a/0x9ff
>> [   34.099902]  process_one_work+0x1cc/0x360
>> [   34.100384]  worker_thread+0x45/0x3b0
>> [   34.100851]  ? process_one_work+0x360/0x360
>> [   34.101308]  kthread+0xf6/0x130
>> [   34.101728]  ? kthread_park+0x80/0x80
>> [   34.102186]  ret_from_fork+0x1f/0x30
>>
>> [   34.640751] task:kworker/u10:9   state:D stack:14528 pid:  255 ppid:     2 flags:0x00004000
>> [   34.641253] Workqueue: events_unbound async_run_entry_fn
>> [   34.641722] Call Trace:
>> [   34.642217]  __schedule+0x275/0x6c0
>> [   34.642683]  schedule+0x41/0xa0
>> [   34.643179]  schedule_timeout+0x18b/0x290
>> [   34.643645]  ? del_timer_sync+0x30/0x30
>> [   34.644131]  __down_timeout+0x6b/0xc0
>> [   34.644568]  ? ufshcd_clkscale_enable_show+0x20/0x20
>> [   34.645014]  ? async_schedule_node_domain+0x17d/0x190
>> [   34.645496]  down_timeout+0x42/0x50
>> [   34.645947]  ufshcd_wl_suspend+0x79/0xa0
>> [   34.646432]  ? scmd_printk+0x100/0x100
>> [   34.646917]  scsi_bus_suspend_common+0x56/0xc0
>> [   34.647405]  ? scsi_bus_freeze+0x10/0x10
>> [   34.647858]  dpm_run_callback+0x45/0x110
>> [   34.648347]  __device_suspend+0x117/0x460
>> [   34.648788]  async_suspend+0x16/0x90
>> [   34.649251]  async_run_entry_fn+0x26/0x110
>> [   34.649676]  process_one_work+0x1cc/0x360
>> [   34.650137]  worker_thread+0x45/0x3b0
>> [   34.650563]  ? process_one_work+0x360/0x360
>> [   34.650994]  kthread+0xf6/0x130
>> [   34.651455]  ? kthread_park+0x80/0x80
>> [   34.651882]  ret_from_fork+0x1f/0x30
>>
>>
>>
>>>
>>>>
>>>> I'll address the other comments in the next version.
>>>>
>>>>
>>>> Thank you!
>>>>
>>>>>> -    pm_runtime_put(hba->dev);
>>>>>> +    ufshcd_rpm_put(hba);
>>>>>>    }
>>>>>
>>>>> <SNIP>
>>>>>
>>>>>> +void ufshcd_resume_complete(struct device *dev)
>>>>>> +{
>>>>
>>>
>>
> 
>