On Tue, Jun 30, 2020 at 12:23:12PM -0700, Bart Van Assche wrote: > On 2020-06-30 11:02, Alan Stern wrote: > > Right now there doesn't seem to be any mechanism for resuming the queue > > if an REQ_PREEMPT request is added while the queue is suspended. > > I do not agree with the above statement. My understanding is that resuming > happens as follows if a request is submitted against a runtime suspended > queue owned by a SCSI LLD: > > blk_queue_enter() > -> blk_pm_request_resume()
Assume that BLK_MQ_REQ_PREEMPT is set in flags. Then where exactly does blk_queue_enter(q, flags) call blk_pm_request_resume(q)? Nowhere, as far as I can see. Alan Stern > -> pm_request_resume(dev) > -> __pm_runtime_resume(dev, RPM_ASYNC) > -> rpm_resume(dev, RPM_ASYNC) > -> dev->power.request = RPM_REQ_RESUME; > -> queue_work(pm_wq, &dev->power.work) > -> pm_runtime_work() > -> rpm_resume(dev, RPM_NOWAIT) > -> callback = scsi_runtime_resume; > -> rpm_callback(callback, dev); > -> scsi_runtime_resume(dev); > -> sdev_runtime_resume(dev); > -> blk_pre_runtime_resume(sdev->request_queue); > -> q->rpm_status = RPM_RESUMING; > -> sd_resume(dev); > -> sd_start_stop_device(sdkp); > -> sd_pm_ops.runtime_resume == scsi_execute(sdp, > START); > -> blk_get_request(..., ..., BLK_MQ_REQ_PREEMPT) > -> blk_mq_alloc_request() > -> blk_queue_enter() > -> __blk_mq_alloc_request() > -> blk_execute_rq() > -> blk_put_request() > -> blk_post_runtime_resume(sdev->request_queue); > -> q->rpm_status = RPM_ACTIVE; > -> pm_runtime_mark_last_busy(q->dev); > -> pm_request_autosuspend(q->dev); > > Bart.
