On 9/15/21 8:35 AM, Adrian Hunter wrote:

Thanks for the idea.  Unfortunately it does not work for pass-through
requests, refer scsi_noretry_cmd().  sdev_ufs_device and sdev_rpmb are
used with pass-through requests.

How about allocating and submitting the REQUEST SENSE command from the context
of a workqueue, or in other words, switching back to scsi_execute()? Although
that approach doesn't guarantee that the unit attention condition is cleared
before the first SCSI command is received from outside the UFS driver, I don't
see any other solution since my understanding is that the deadlock between
blk_mq_freeze_queue() and blk_get_request() from inside ufshcd_err_handler()
can also happen without "ufs: Synchronize SCSI and UFS error handling".

The only code I know of that relies on the UFS driver clearing unit attentions
is this code:
https://android.googlesource.com/platform/system/core/+/master/trusty/storage/proxy/rpmb.c
The code that submits a REQUEST SENSE was added in the UFS driver as the result
of a request from the team that maintains the Trusty code. Earlier today I have
been promised that unit attention handling support will be added in Trusty but I
do not when this will be realized.

Bart.