linux-kernel - Re: [PATCH v4] scsi: ufs: core: Don't perform UFS clkscale if host asyn scan in progress

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Message-ID: <81e403f0-51b4-4efd-a06c-c6d7b02802dd@quicinc.com>
Date: Tue, 5 Aug 2025 14:03:24 +0800
From: Ziqi Chen <quic_ziqichen@...cinc.com>
To: Peter Wang (王信友) <peter.wang@...iatek.com>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "avri.altman@....com"
	<avri.altman@....com>,
        "neil.armstrong@...aro.org"
	<neil.armstrong@...aro.org>,
        "quic_cang@...cinc.com" <quic_cang@...cinc.com>,
        "quic_nitirawa@...cinc.com" <quic_nitirawa@...cinc.com>,
        "quic_nguyenb@...cinc.com" <quic_nguyenb@...cinc.com>,
        "bvanassche@....org"
	<bvanassche@....org>,
        "luca.weiss@...rphone.com" <luca.weiss@...rphone.com>,
        "konrad.dybcio@....qualcomm.com" <konrad.dybcio@....qualcomm.com>,
        "junwoo80.lee@...sung.com" <junwoo80.lee@...sung.com>,
        "mani@...nel.org"
	<mani@...nel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "quic_rampraka@...cinc.com" <quic_rampraka@...cinc.com>
CC: "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        Tze-nan Wu (吳澤南) <Tze-nan.Wu@...iatek.com>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "manivannan.sadhasivam@...aro.org" <manivannan.sadhasivam@...aro.org>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "James.Bottomley@...senPartnership.com"
	<James.Bottomley@...senPartnership.com>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] scsi: ufs: core: Don't perform UFS clkscale if host
 asyn scan in progress



On 8/4/2025 8:43 PM, Peter Wang (王信友) wrote:
> On Mon, 2025-08-04 at 15:54 +0800, Ziqi Chen wrote:
>>
>> Hi  Peter && Bart,
>>
>> How do you think about using
>>
>> if (!mutex_trylock(&hba->host->scan_mutex))
>>          return -EAGAIN;
>>
>> instead of
>>
>> mutex_lock(&hba->host->scan_mutex);
>>
>> But this way will cause one line print of devfreq failed.
>>
>> BRs
>> Ziqi
> 
> 
> Hi Ziqi,
> 
> After applying the patch below, the lockdep issue no longer appears.
> Would you be able to upstream this fix?
> 
> ---
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 2ff91f2..0af34ce 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -1435,7 +1435,8 @@ static int ufshcd_clock_scaling_prepare(struct
> ufs_hba *hba, u64 timeout_us)
>   	 * make sure that there are no outstanding requests when
>   	 * clock scaling is in progress
>   	 */
> -	mutex_lock(&hba->host->scan_mutex);
> +	if(!mutex_trylock(&hba->host->scan_mutex))
> +		return -EAGAIN;
>   	blk_mq_quiesce_tagset(&hba->host->tag_set);
>   	mutex_lock(&hba->wb_mutex);
>   	down_write(&hba->clk_scaling_lock);
> 
> 
> Thanks.
> Peter

Hi Peter,

I saw you raised a ACK change to revert this whole change on branch
Android16-6.12. Without this change, you will meet stuck issue during
stability reboot test due to request queue quiesce and unquiesce
mismatch.

This lockdep print just a warning, and as per my analysis before, This
is a misjudgment. But stuck/crash issue is a real issue which has real 
instance.

Can you abort your reverting change?


BRs,
Ziqi