Re: [PATCH V3 1/3] scsi: ufs: Fix error handler clear ua deadlock

[Adrian Hunter <adrian.hunter@intel.com>]

On 16/09/21 1:41 am, Bart Van Assche wrote:
> 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 issue can also be fixed by sending REQUEST SENSE directly avoiding the
SCSI queues.  Please see V4.

> 
> 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.
> 
>