On Thu, May 27, 2010 at 07:15:31PM +0200, Thomas Gleixner wrote: > On Thu, 27 May 2010, Matthew Garrett wrote: > > You still need the in-kernel suspend blockers if you want to guarantee > > that you can't lose wakeup events. But yes, if you're not concerned > > handling badly behaved applications then I believe that you can lose > > opportunistic suspend and just use the scheduler. > > No, we do not. We need correctly implemented drivers and a safe > switchover from normal event delivery to wakeup based. What is a "Correctly implemented driver" in this case? One that receives a wakeup event and then prevents suspend being entered until userspace has acknowledged that event? Because that's what an in-kernel suspend blocker is. > > My question was about explicit suspend states, not implicitly handling > > an identical state based on scheduler constraints. Suspend-as-a-C-state > > isn't usable on x86 - you have to explicitly trigger it based on some > > And why not ? Just because suspend is not implemented as an ACPI > C-state ? > > Nonsense, if we want to push the system into suspend from the idle > state we can do that. It's just not implemented and we've never tried > to do it as it requires a non trivial amount of work, but I have done > it on an ARM two years ago as a prove of concept and it works like a > charm. ACPI provides no guarantees about what level of hardware functionality remains during S3. You don't have any useful ability to determine which events will generate wakeups. And from a purely practical point of view, since the latency is in the range of seconds, you'll never have a low enough wakeup rate to hit it. > > policy. And if you want to be able to do that without risking the loss > > of wakeup events then you need in-kernel suspend blockers. > > Crap. Stop beating on those lost wakeup events. If we lose them then > the drivers are broken and do not handle the switch over correctly. Or > the suspend mechanism is broken as it does not evaluate the system > state correctly. Blockers are just papering over that w/o tackling the > real problem. Ger;kljaserf;kljf;kljer;klj. Suspend blockers are the mechanism for the driver to indicate whether the wakeup event has been handled. That's what they're there for. The in-kernel ones don't paper over anything. -- Matthew Garrett | mjg59@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
