Il 23/10/2012 14:04, Jan Kiszka ha scritto: >>> >> >>> >> So the stop_machine idea is thrown away? >> > >> > IIRC I convinced myself that it's just as bad. > One tricky part with stop machine is that legacy code may trigger it > while holding the BQL, does not expect to lose that lock even for a > brief while, but synchronizing on other threads does require dropping > the lock right now. Maybe an implementation detail, but at least a nasty > one.
But it would only be triggered by hot-unplug, no? That is already an asynchronous action, so it is not a problem to delay the actual stop_machine+qdev_free (and just that part!) to a bottom half or another place when it is safe to drop the BQL. Paolo
