On Mon, 28 May 2007, Pavel Machek wrote: > > The theoretical answer is that it behaves the way we want. The kernel > > thread does selective resumes in response to device requests. If such > > a request comes in while the system is asleep it will awaken the > > system; so it's only logical that a request coming in while the system > > is in the process of going to sleep should abort the suspend. > > I'd say that it shows ppc being broken. User wanted to suspend the > system, and now unrelated task did lsusb... and system will not sleep. > > AFAICT it is DoS issue -- if one of your users keeps doing lsusb, root > will not be able to suspend the system. This is a matter of one's philosophy. In suspend-to-RAM, should tasks be frozen or should I/O queues be frozen? With the USB subsystem I have followed the approach taken by the PM core, which is that tasks are frozen. But one can -- and Linus has on at least one occasion -- make a good case that tasks should be left running while only I/O is frozen. This would require the subsystem to distinguish between a selective device suspend and a system-wide suspend-to-RAM, so that selective resume could be enabled on demand in one case but not the other. It's quite doable in principle -- it's just not the technique I used. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
