On 07/27/2017 08:47 AM, Bart Van Assche wrote: > On Thu, 2017-07-27 at 08:02 -0600, Jens Axboe wrote: >> The bug looks like SCSI running the queue inline from IRQ >> context, that's not a good idea. Can you confirm the below works for >> you? >> >> >> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c >> index f6097b89d5d3..78740ebf966c 100644 >> --- a/drivers/scsi/scsi_lib.c >> +++ b/drivers/scsi/scsi_lib.c >> @@ -497,7 +497,7 @@ static void scsi_run_queue(struct request_queue *q) >> scsi_starved_list_run(sdev->host); >> >> if (q->mq_ops) >> - blk_mq_run_hw_queues(q, false); >> + blk_mq_run_hw_queues(q, true); >> else >> blk_run_queue(q); >> } > > Hello Jens, > > 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. > 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. -- Jens Axboe
