On Fri 2009-12-11 14:48:21, Alexey Starikovskiy wrote: > Lin Ming ??????????: > > On Thu, 2009-12-10 at 20:21 +0800, Alexey Starikovskiy wrote: > >> Hi Xiaotian, > >> > >> I think, this is another round of "armor vs. bullet" race... It will hold until > >> might_sleep() logic changes again. > >> > >> Please consider using preemptible() -- IMHO this is the check we should perform > >> in our case of voluntary preemption. > > > > preemptible() may not work here because it always returns 0 for > > non-preemptible kernel. > Right, and it means that this machine does not care about low latency that much. > The reason we introduced the preemption point in the first place, was unacceptable latency > due to very long AML methods on some machines. We don't need this preemption point for normal > operation, this is exactly what voluntary preemption does -- allows those in hurry to pass by. > If there are none, fine. > > > > #ifdef CONFIG_PREEMPT > > # define preemptible() (preempt_count() == 0 && !irqs_disabled()) > > # define IRQ_EXIT_OFFSET (HARDIRQ_OFFSET-1) > > #else > > # define preemptible() 0 > > # define IRQ_EXIT_OFFSET HARDIRQ_OFFSET > > #endif Well, normally we want low latency even for !CONFIG_PREEMPT kernels. Actually, explicit preemption points are NOPs for CONFIG_PREEMPT kernels, right? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
