* Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> [100506 11:42]: > On Thu, 6 May 2010, Tony Lindgren wrote: > > > Well if your hardware runs off-while-idle or even just > > retention-while-idle, then the basic shell works just fine waking up > > every few seconds or so. > > > > Then you could keep init/shell/suspend policy deamon running until > > it's time to suspend the whole device. To cut down runaway timers, > > you could already freeze the desktop/GUI/whatever earlier. > > This comes down mostly to efficiency. Although the suspend blocker > patch does the actual suspending in a workqueue thread, AFAIK there's > no reason it couldn't use a user thread instead. > > The important difference lies in what happens when a suspend fails > because a driver is busy. Without suspend blockers, the kernel has to > go through the whole procedure of freezing userspace and kernel threads > and then suspending a bunch of drivers before hitting the one that's > busy. Then all that work has to be undone. By contrast, with suspend > blockers the suspend attempt can fail right away with minimal overhead. But does that really matter if you're only few tens of times times per day or so? I don't understand why you would want to try to suspend except after some timeout of no user or network activity. > There's also a question of reliability. With suspends controlled by > userspace there is a possibility of races, which could lead the system > to suspend when it shouldn't. With control in the kernel, these races > can be eliminated. I agree the suspend needs to happen without races. But I think the logic for when to suspend should be done in the userspace as it can be device or user specific. Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
