On 11/03/2017 07:55 PM, Ming Lei wrote: > It is very expensive to atomic_inc/atomic_dec the host wide counter of > host->busy_count, and it should have been avoided via blk-mq's mechanism > of getting driver tag, which uses the more efficient way of sbitmap queue. > > Also we don't check atomic_read(&sdev->device_busy) in scsi_mq_get_budget() > and don't run queue if the counter becomes zero, so IO hang may be caused > if all requests are completed just before the current SCSI device > is added to shost->starved_list.
This looks like an improvement. I have added it for 4.15. Bart, does this fix your hang? -- Jens Axboe
