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

On 22/04/21 7:38 pm, Asutosh Das (asd) wrote:

On 4/20/2021 12:42 AM, Adrian Hunter wrote:

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On 20/04/21 7:15 am, Adrian Hunter wrote:

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On 20/04/21 12:53 am, Asutosh Das (asd) wrote:

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On 4/19/2021 11:37 AM, Adrian Hunter wrote:

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On 16/04/21 10:49 pm, Asutosh Das wrote:

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Co-developed-by: Can Guo <redacted>
Signed-off-by: Can Guo <redacted>
Signed-off-by: Asutosh Das <redacted>
---

I came across 3 issues while testing.  See comments below.

Hi Adrian
Thanks for the comments.

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<SNIP>

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@@ -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

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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

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I'll address the other comments in the next version.


Thank you!

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-    pm_runtime_put(hba->dev);
+    ufshcd_rpm_put(hba);
   }

<SNIP>

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+void ufshcd_resume_complete(struct device *dev)
+{

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