linux-kernel - Re: [PATCH v3 1/9] scsi: ufs: Differentiate status between hba pm ops and wl pm ops

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Date:   Wed, 23 Jun 2021 09:32:28 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Bart Van Assche <bvanassche@....org>
Cc:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, ziqichen@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kiwoong Kim <kwmad.kim@...sung.com>,
        Satya Tangirala <satyat@...gle.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/9] scsi: ufs: Differentiate status between hba pm ops
 and wl pm ops

Hi Bart,

On 2021-06-17 01:50, Bart Van Assche wrote:
> On 6/9/21 9:43 PM, Can Guo wrote:
>> @@ -8784,7 +8786,7 @@ static int __ufshcd_wl_suspend(struct ufs_hba 
>> *hba, enum ufs_pm_op pm_op)
>>  	enum ufs_dev_pwr_mode req_dev_pwr_mode;
>>  	enum uic_link_state req_link_state;
>> 
>> -	hba->pm_op_in_progress = true;
>> +	hba->wl_pm_op_in_progress = true;
>>  	if (pm_op != UFS_SHUTDOWN_PM) {
>>  		pm_lvl = pm_op == UFS_RUNTIME_PM ?
>>  			 hba->rpm_lvl : hba->spm_lvl;
>> @@ -8919,7 +8921,7 @@ static int __ufshcd_wl_suspend(struct ufs_hba 
>> *hba, enum ufs_pm_op pm_op)
>>  		hba->clk_gating.is_suspended = false;
>>  		ufshcd_release(hba);
>>  	}
>> -	hba->pm_op_in_progress = false;
>> +	hba->wl_pm_op_in_progress = false;
>>  	return ret;
>>  }
> 
> Are the __ufshcd_wl_suspend() calls serialized in any way? If not, will
> the value of wl_pm_op_in_progress be incorrect if multiple kernel
> threads run __ufshcd_wl_suspend() concurrently and one of the
> __ufshcd_wl_suspend() instances returns earlier than the other?
> 

Sorry for getting back late on this... I was stuck by some urgent 
issues.

Yes, __ufshcd_wl_suspend() calls are serilized, because it is called by
either runtime suspend or system suspend, and runtime suspend and system
suspend are serialized - Rafael J. Wysocki has put a lot of efforts on 
it,
see also 1e2ef05bb8cf8 ("PM: Limit race conditions between runtime PM 
and
system sleep (v2)")).

> Thanks,
> 
> Bart.