Messages in this thread Patch in this message |  | | Subject | RE: [PATCH v3] scsi: ufs: Cleanup completed request without interrupt notification | From | Stanley Chu <> | Date | Sun, 12 Jul 2020 09:26:00 +0800 |
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Hi Avri,
On Thu, 2020-07-09 at 08:31 +0000, Avri Altman wrote: > > > > 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?
Sure.
If a request using tag N is completed by UFS device without interrupt notification till timeout happens, ufshcd_abort() will be invoked.
Since request completion flow is not executed, current status may be
- Tag N in hba->outstanding_reqs is set - Tag N in doorbell register is not set
In this case, ufshcd_abort() flow would be
- This log is printed: "ufshcd_abort: cmd was completed, but without a notifying intr, tag = N" - This log is printed: "ufshcd_abort: Device abort task at tag N" - If hba->req_abort_skip is zero, QUERY_TASK command is sent - Device responds "UPIU_TASK_MANAGEMENT_FUNC_COMPL" - This log is printed: "ufshcd_abort: cmd at tag N not pending in the device." - Doorbell tells that tag N is not set, so the driver goes to label "out" with this log printed: "ufshcd_abort: cmd at tag %d successfully cleared from DB." - In label "out" section, no cleanup will be made, and then ufshcd_abort exits - This request will be re-queued to request queue by SCSI timeout handler
Now, Inconsistent state shows-up: A request is "re-queued" but its corresponding resource in UFS layer is not cleared, below flow will trigger bad things,
- A new request with tag M is finished - Interrupt is raised and ufshcd_transfer_req_compl() found both tag N and M can process the completion flow - The post-processing flow for tag N will be executed while its request is still alive
I am sorry that below messages are only for old kernel in non-blk-mq case. However above scenario will also trigger bad thing in blk-mq case.
> > > > > 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
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