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

From: Asutosh Das (asd)
Date: Thu Apr 22 2021 - 12:39:16 EST


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 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.
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)
+{





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