On Sun, Sep 28, 2014 at 06:57:18PM +0800, Li Yang wrote: > On Fri, Sep 26, 2014 at 9:20 PM, Mark Rutland <mark.rutl...@arm.com> wrote: > >> > This looks to be a carbon copy of the vexpress pseudo-hotplug in > >> > arch/arm/mach-vexpress/hotplug.c, which is obviously broken in the way > >> > you describe above. Perhaps we should go about ripping that out? > >> > >> The Versatile Express does not support suspend so the only problem case > >> is kexec. However, isn't this support needed for big.LITTLE, and as > >> the Versatile Express is the platform which these features get developed > >> on, having working CPU hotplug seems rather fundamental for ARM kernel > >> feature development. > >> > >> In that regard, Versatile Express is something of a special case. > > > > It is admittedly helpful during development to perform pseudo-hotplug on > > Versatile Express. I have a local patch adding vexpress_cpu_disable so I > > can test for bugs that only trigger if CPU0 is hotplugged. > > > > Given that, perhaps we should make it clearer that Versatile Express is > > not a reference implementation for CPU hotplug; add some Kconfig (e.g. > > VEXPRESS_PSEUDO_HOTPLUG) that depends on !KEXEC && !SUSPEND, and putting > > a note in hotplug.c stating it's not suitable as a reference > > implementation. > > > > ...but perhaps that's overkill. > > I agree that the pseudo-hotplug is breaking the kexec. However, I > don't think it breaks the system suspend case as tasks and interrupts > have been moved out of the non-booting CPU. The pseudo-hotplug would > be even better than real hotplug as it introduces less latency.
Sorry, that's not an acceptable reason to use it. NAK. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
