RE: [PATCH v3] scsi: ufs: Cleanup completed request without interrupt notification

[Avri Altman <Avri.Altman@wdc.com>]

 
> 
> If somehow no interrupt notification is raised for a completed request
> and its doorbell bit is cleared by host, UFS driver needs to cleanup
> its outstanding bit in ufshcd_abort().
Theoretically, this case is already accounted for - 
See line 6407: a proper error is issued and eventually outstanding req is cleared.

Can you go over the scenario you are attending line by line,
And explain why ufshcd_abort does not account for it?

> 
> Otherwise, system may crash by below abnormal flow:
> 
> After this request is requeued by SCSI layer with its
> outstanding bit set, the next completed request will trigger
> ufshcd_transfer_req_compl() to handle all "completed outstanding
> bits". In this time, the "abnormal outstanding bit" will be detected
> and the "requeued request" will be chosen to execute request
> post-processing flow. This is wrong and blk_finish_request() will
> BUG_ON because this request is still "alive".
> 
> It is worth mentioning that before ufshcd_abort() cleans the timed-out
> request, driver need to check again if this request is really not
> handled by __ufshcd_transfer_req_compl() yet because it may be
> possible that the interrupt comes very lately before the cleaning.
What do you mean? Why checking the outstanding reqs isn't enough?

> 
> Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
> ---
>  drivers/scsi/ufs/ufshcd.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 8603b07045a6..f23fb14df9f6 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -6462,7 +6462,7 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
>                         /* command completed already */
>                         dev_err(hba->dev, "%s: cmd at tag %d successfully cleared from
> DB.\n",
>                                 __func__, tag);
> -                       goto out;
> +                       goto cleanup;
But you've arrived here only if (!(test_bit(tag, &hba->outstanding_reqs))) - 
See line 6400. 

>                 } else {
>                         dev_err(hba->dev,
>                                 "%s: no response from device. tag = %d, err %d\n",
> @@ -6496,9 +6496,14 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
>                 goto out;
>         }
> 
> +cleanup:
> +       spin_lock_irqsave(host->host_lock, flags);
> +       if (!test_bit(tag, &hba->outstanding_reqs)) {
> +               spin_unlock_irqrestore(host->host_lock, flags);
> +               goto out;
> +       }
>         scsi_dma_unmap(cmd);
> 
> -       spin_lock_irqsave(host->host_lock, flags);
>         ufshcd_outstanding_req_clear(hba, tag);
>         hba->lrb[tag].cmd = NULL;
>         spin_unlock_irqrestore(host->host_lock, flags);
> --
> 2.18.0