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

[Ziqi Chen <quic_ziqichen@quicinc.com>]

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