Jens Axboe [off-list ref] writes:

On 07/27/2017 08:47 AM, Bart Van Assche wrote:

quoted

On Thu, 2017-07-27 at 08:02 -0600, Jens Axboe wrote:

quoted

The bug looks like SCSI running the queue inline from IRQ
context, that's not a good idea.

...

quoted

scsi_run_queue() works fine if no scheduler is configured. Additionally, that
code predates the introduction of blk-mq I/O schedulers. I think it is
nontrivial for block driver authors to figure out that a queue has to be run
from process context if a scheduler has been configured that does not support
to be run from interrupt context.

No it doesn't, you could never run the queue from interrupt context with
async == false. So I don't think that's confusing at all, you should
always be aware of the context.

quoted

How about adding WARN_ON_ONCE(in_interrupt()) to
blk_mq_start_hw_queue() or replacing the above patch by the following:

No, I hate having dependencies like that, because they always just catch
one of them. Looks like the IPR path that hits this should just offload
to a workqueue or similar, you don't have to make any scsi_run_queue()
async.

OK, so the resolution is "fix it in IPR" ?

cheers