[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/6] xen-blkfront: avoid to use start/stop queue
On Tue, Jul 11, 2017 at 06:41:29PM +0000, Bart Van Assche wrote: > On Wed, 2017-07-12 at 02:20 +0800, Ming Lei wrote: > > This interfaces will be removed soon, so use quiesce and > > unquiesce instead, which should be more safe. > > > > The only one usage will be removed in the following > > congestion control patches. > > Hello Ming, > > The title of this patch is misleading since this patch does not touch the > calls > related to queue congestion (blk_mq_stop_hw_queue() and > blk_mq_start_stopped_hw_queues()). I assume that you meant that this patch > avoids > that the xen-blkfront driver uses blk_mq_(start|stop)_hw_queues() (with > queues in > plural form)? Can you please reflect that in the subject of this and related > patches? > > Additionally, it's probably a good idea that this is not just an interface > change > but that this kind of patches fix a (hard to trigger?) race condition. > > > static inline void kick_pending_request_queues_locked(struct > > blkfront_ring_info *rinfo) > > { > > - if (!RING_FULL(&rinfo->ring)) > > + if (!RING_FULL(&rinfo->ring)) { > > blk_mq_start_stopped_hw_queues(rinfo->dev_info->rq, true); > > + blk_mq_kick_requeue_list(rinfo->dev_info->rq); > > + } > > } > > > > static void kick_pending_request_queues(struct blkfront_ring_info *rinfo) > > @@ -1225,7 +1227,8 @@ static void kick_pending_request_queues(struct > > blkfront_ring_info *rinfo) > > unsigned long flags; > > > > spin_lock_irqsave(&rinfo->ring_lock, flags); > > - kick_pending_request_queues_locked(rinfo); > > + if (!RING_FULL(&rinfo->ring)) > > + blk_mq_run_hw_queues(rinfo->dev_info->rq, true); > > spin_unlock_irqrestore(&rinfo->ring_lock, flags); > > } > > Why do some kick_pending_request_queues_locked() kick the requeue list and why > has the above kick_pending_request_queues_locked() call been converted into a > blk_mq_run_hw_queues() call and thereby ignores the requeue list? Looks I forget to reply the question about requeue list. Actually blk_mq_kick_requeue_list() is only needed run where the queue is restarted, so this patch moves it after blk_mq_start_stopped_hw_queues(). In other path, we don't stop queue anymore, so needn't to kick requeue list. -- Ming _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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