On Fri, 16 Mar 2012, Tejun Heo wrote: > On Fri, Mar 16, 2012 at 05:10:48PM -0400, Alan Stern wrote: > > I don't understand. How would we miss a change of medium if we cancel > > the existing work item and resubmit in on a non-freezable workqueue? > > > > If the work item wasn't queued to begin with, cancelling it won't > > change anything. If the work item has already started running, > > cancelling it won't do anything. > > > > If the work item is queued but hasn't started running yet (perhaps > > because the workqueue is already frozen), the cancel call will succeed > > and then the work item will run on the non-freezable workqueue. In > > turn, the freezer will wait until disk_clear_events() finishes, which > > means it will wait until the work item finishes. > > > > Either way, the medium change will be detected. The one danger is that > > after the work item is cancelled, some other thread might resubmit it > > to the freezable workqueue before it can be put on the non-freezable > > workqueue. > > Why not just lock out freezing across that issue / flush section? Currently there is no way to lock out freezing. Besides, it may already have started. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
