Messages in this thread | | | Date | Wed, 29 Mar 2006 14:47:46 -0800 | From | Andrew Morton <> | Subject | Re: [rfc] fix Kconfig, hotplug_cpu is needed for swsusp |
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Pavel Machek <pavel@ucw.cz> wrote: > > HOTPLUG_CPU is needed on normal PCs, too -- it is neccessary for > software suspend. > > Signed-off-by: Pavel Machek <pavel@suse.cz> > > --- > commit 2206dab43d50723d6b15caa8821e8d97c6b5ef28 > tree cbfc324e15d216aa91ce6a51927668076de5b7db > parent dd76aabd03933b80c61fa5b0c0c995950246c603 > author <pavel@amd.ucw.cz> Thu, 30 Mar 2006 00:06:31 +0200 > committer <pavel@amd.ucw.cz> Thu, 30 Mar 2006 00:06:31 +0200 > > arch/i386/Kconfig | 8 ++++---- > kernel/power/process.c | 3 +-- > kernel/signal.c | 1 + > 3 files changed, 6 insertions(+), 6 deletions(-) > > diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig > index f7db71d..955dc08 100644 > --- a/arch/i386/Kconfig > +++ b/arch/i386/Kconfig > @@ -741,12 +741,12 @@ config PHYSICAL_START > > config HOTPLUG_CPU > bool "Support for hot-pluggable CPUs (EXPERIMENTAL)" > - depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER && !X86_PC > + depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER > ---help--- > - Say Y here to experiment with turning CPUs off and on. CPUs > - can be controlled through /sys/devices/system/cpu. > + Say Y here to experiment with turning CPUs off and on, and to > + enable suspend on SMP systems. CPUs can be controlled through > + /sys/devices/system/cpu. > > - Say N. >
OK, this will get ugly. APICs are involved.
That patch simply undoes this one:
> [PATCH] x86: make CONFIG_HOTPLUG_CPU depend on !X86_PC > > Make CONFIG_HOTPLUG_CPU depend on !X86_PC, so we need to turn on either > CONFIG_GENERICARCH, CONFIG_BIGSMP or any other subarch except X86_PC when > CONFIG_HOTPLUG_CPU=y > > With 2.6.15+ kernels when CONFIG_HOTPLUG_CPU is turned on we switch to > bigsmp mode for sending IPI's and ioapic configurations that caused the > following error message. > > >> More than 8 CPUs detected and CONFIG_X86_PC cannot handle it. > >> Use CONFIG_X86_GENERICARCH or CONFIG_X86_BIGSMP. > > Originally bigsmp was added just to handle >8 cpus, but now with hotplug > cpu support we need to use bigsmp mode (why? see below), that cause the > above error message even if there were less than 8 cpus in the system. > > The message is bogus, but we are cannot use logical flat mode due to issues > with broadcast IPI can confuse a CPU just comming up. We use flat physical > mode just like x86_64 case. More details on why bigsmp now uses flat > physical mode (vs. cluster mode) in following link. > > http://marc.theaimsgroup.com/?l=linux-kernel&m=113261865814107&w=2 >
Which I was distinctly uncomfortable with. (And glad I nixed it for 2.6.16 ;))
Ashok, we need to do something better, but what? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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