Hello, On Thu, Apr 04, 2013 at 10:16:39PM +0800, Aaron Lu wrote: > It probably wouldn't happen for normal user, only for some SCSI driver > developers like me, e.g. the sr_mod will normally load during boot, and > when I made some changes to the code, I'll unload the driver and reload > it. This is found when I was developing ZPODD code and I just found some > time to see what happened.
Does that unregister and register the same queue? Ah, crap, it does. > The queue for the scsi device will always be there, the queue(and the > device) will not go away on driver unregistration. So it will be left in > normal mode, and on next blk_register_queue call, the warning will show > up. > > > Starting a bypass mode can be very expensive and some drivers create > > and destroy a lot of queues during probing. We don't want a call to > > blk_queue_bypass_start() on every queue creation / destruction cycle. > > By expensive, do you mean the drain of the queue? Since the queue is to > be unregistered, I suppose the queue has to be drained somewhere? The problematic one is synchronize_rcu(). It adds up pretty quickly. I'd suggest just skipping blk_queue_bypass_end() during registration if the queue is not bypassing. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
