Re: [PATCH v4 10/10] scsi: ufs: Apply more limitations to user access

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On 2021-06-25 06:25, Bart Van Assche wrote:
On 6/23/21 7:23 PM, Can Guo wrote:
On 2021-06-24 05:51, Bart Van Assche wrote:
On 6/23/21 12:35 AM, Can Guo wrote:
- During system suspend, user space software is paused before the device   driver freeze callbacks are invoked. Hence, the hba->is_sys_suspended
  check can be left out.

is_sys_suspended indicates that system resume failed (power/clk is OFF).

- If a LUN is runtime suspended, it should be resumed if accessed from   user space instead of failing user space accesses. In other words, the
  hba->is_wlu_sys_suspended check seems inappropriate to me.

hba->is_wlu_sys_suspended indicates that wl system resume failed, device
is not operational.

Hi Can,

Thanks for the clarification. How about converting the above two answers
into comments inside ufshcd_is_user_access_allowed()?


Sure.

Should ufshcd_is_user_access_allowed() perhaps be called after
ufshcd_rpm_get_sync() instead of before to prevent that the value of
hba->is_sys_suspended or hba->is_wlu_sys_suspended changes after having
been checked and before the UFS device is accessed?


is_sys_suspended and is_wlu_sys_suspended only represent system PM status,
not runtime PM status.

My understanding is that user threads are frozen before system PM starts,
so it does not matter we call  ufshcd_is_user_access_allowed() before or
after ufshcd_rpm_get_sync().

If my understanding is wrong, then we need to either call lock_system_sleep() in get_user_access() or wrap ufshcd_suspend_prepare/ufshcd_resume_complete()
with host_sem.

Thanks,

Can Guo.

Thanks,

Bart.



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