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

[Bart Van Assche]

On 7/12/24 2:43 AM, peter.wang at mediatek.com 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.