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From:   Avri Altman <Avri.Altman@wdc.com>
To:     Stanley Chu <stanley.chu@mediatek.com>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
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Subject: RE: [PATCH v3] scsi: ufs: Cleanup completed request without interrupt
 notification
Thread-Topic: [PATCH v3] scsi: ufs: Cleanup completed request without
 interrupt notification
Thread-Index: AQHWU5heDqJFApuOo0yQOIjuO+/O36j+4j7g
Date:   Thu, 9 Jul 2020 08:31:38 +0000
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References: <20200706132113.21096-1-stanley.chu@mediatek.com>
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=20
>=20
> 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 -=20
See line 6407: a proper error is issued and eventually outstanding req is c=
leared.

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

>=20
> Otherwise, system may crash by below abnormal flow:
>=20
> 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".
>=20
> 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?

>=20
> Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
> ---
>  drivers/scsi/ufs/ufshcd.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>=20
> 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))) =
-=20
See line 6400.=20

>                 } else {
>                         dev_err(hba->dev,
>                                 "%s: no response from device. tag =3D %d,=
 err %d\n",
> @@ -6496,9 +6496,14 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
>                 goto out;
>         }
>=20
> +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);
>=20
> -       spin_lock_irqsave(host->host_lock, flags);
>         ufshcd_outstanding_req_clear(hba, tag);
>         hba->lrb[tag].cmd =3D NULL;
>         spin_unlock_irqrestore(host->host_lock, flags);
> --
> 2.18.0