Re: [PATCH v1] ufs: core: fix deadlock when rtc update

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On 7/12/24 2:43 AM, peter.wang@xxxxxxxxxxxx wrote:
Three have deadlock when runtime suspend wait flush rtc work,
and rtc work call ufshcd_rpm_put_sync to wait runtime resume.

"Three have"? The above description is very hard to understand. Please
improve it.

-	 /* Update RTC only when there are no requests in progress and UFSHCI is operational */
-	if (!ufshcd_is_ufs_dev_busy(hba) && hba->ufshcd_state == UFSHCD_STATE_OPERATIONAL)
+	 /*
+	  * Update RTC only when
+	  * 1. there are no requests in progress
+	  * 2. UFSHCI is operational
+	  * 3. pm operation is not in progress
+	  */
+	if (!ufshcd_is_ufs_dev_busy(hba) &&
+	    hba->ufshcd_state == UFSHCD_STATE_OPERATIONAL &&
+	    !hba->pm_op_in_progress)
  		ufshcd_update_rtc(hba);
if (ufshcd_is_ufs_dev_active(hba) && hba->dev_info.rtc_update_period)

The above seems racy to me. I don't think there is any mechanism that
prevents that hba->pm_op_in_progress is set after it has been checked
and before ufshcd_update_rtc() is called. Has it been considered to add
an ufshcd_rpm_get_sync_nowait() call before the hba->pm_op_in_progress
check and a ufshcd_rpm_put_sync() call after the ufshcd_update_rtc()
call?

Thanks,

Bart.




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