Re: [PATCH v4] scsi: ufs: Cleanup completed request without interrupt notification

Bart Van Assche
2020-07-31T04:06:50Z

On 2020-07-30 18:30, Stanley Chu wrote:
> On Mon, 2020-07-27 at 11:18 +0000, Avri Altman wrote:
>> Looks good to me.
>> But better wait and see if Bart have any further reservations.
>
> Would you have any further suggestions?

Today is the first time that I took a look at ufshcd_abort(). The
approach of that function looks wrong to me. This is how I think that a
SCSI LLD abort handler should work:
(1) Serialize against the completion path
(__ufshcd_transfer_req_compl()) such that it cannot happen that the
abort handler and the regular completion path both call
cmd->scsi_done(cmd) at the same time. I'm not sure whether an existing
synchronization object can be used for this purpose or whether a new
synchronization object has to be introduced to serialize scsi_done()
calls from __ufshcd_transfer_req_compl() and ufshcd_abort().
(2) While holding that synchronization object, check whether the SCSI
command is still outstanding. If so, submit a SCSI abort TMR to the device.
(3) If the command has been aborted, call scsi_done() and return
SUCCESS. If aborting failed and the command is still in progress, return
FAILED.

An example is available in srp_abort() in
drivers/infiniband/ulp/srp/ib_srp.c.

Bart.