Re: [PATCH v1] scsi: ufs: Fix deadlock issue in ufshcd_wait_for_doorbell_clr()

[John Stultz]

On Mon, Dec 13, 2021 at 8:15 PM Bart Van Assche <bvanassche@xxxxxxx> wrote:
>
> On 12/13/21 3:00 PM, Bean Huo wrote:
> > Call shost_for_each_device() with host->host_lock is held will cause
> > a deadlock situation, which will cause the system to stall (the log
> > as follow). Fix this issue by narrowing the scope of the lock.
>
> Hi Bean,
>
> As you probably know I do not have access to a test setup that supports clock
> scaling. Has the following patch been considered?
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 6d692aae67ce..244eddf0caf8 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1084,7 +1084,9 @@ static u32 ufshcd_pending_cmds(struct ufs_hba *hba)
>         struct scsi_device *sdev;
>         u32 pending = 0;
>
> -       shost_for_each_device(sdev, hba->host)
> +       lockdep_assert_held(hba->host->host_lock);
> +
> +       __shost_for_each_device(sdev, hba->host)
>                 pending += sbitmap_weight(&sdev->budget_map);

We hit the same issue today as well, and this solution works on db845c.

Reported-by: YongQin Liu <yongqin.liu@xxxxxxxxxx>
Reported-by: Amit Pundir <amit.pundir@xxxxxxxxxx>
Tested-by: John Stultz <john.stultz@xxxxxxxxxx>

thanks
-john