Re: [PATCH V6 1/3] scsi: ufs: Fix error handler clear ua deadlock

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

On 01/10/2021 01:10, Bart Van Assche wrote:
> On 9/30/21 5:42 AM, Adrian Hunter wrote:
>> There is no guarantee to be able to enter the queue if requests are
>> blocked. That is because freezing the queue will block entry to the
>> queue, but freezing also waits for outstanding requests which can make
>> no progress while the queue is blocked.
>>
>> That situation can happen when the error handler issues requests to
>> clear unit attention condition. Requests are blocked if the ufshcd_state is
>> UFSHCD_STATE_EH_SCHEDULED_FATAL, which can happen as a result of
>> prior error handler activity. Requests cannot make progress when
>> ufshcd_state is UFSHCD_STATE_EH_SCHEDULED_FATAL, and only the error
>> handler can change that, so if the error handler is waiting to enter
>> the queue and blk_mq_freeze_queue() is waiting for outstanding requests,
>> they will deadlock.
>>
>> Fix by issuing REQUEST_SENSE directly avoiding the SCSI queues, in
>> a similar fashion as other device commands.
> 
> Hi Adrian,
> 
> Although I appreciate all the work that you have done on this patch, there
> is at least one application (the Android Trusty software) that needs the
> RPMB unit attention information to work correctly. Hence my request to drop
> this patch and to integrate the following patch series in the upstream kernel:
> https://lore.kernel.org/linux-scsi/aacbec00-34e8-f082-51a5-15391bf99710@acm.org/T/#t

That's fine.  It is always good to have options.

I made a couple of minor comments on the patch series.