Pavel Machek <[email protected]> wrote:
>
> HOTPLUG_CPU is needed on normal PCs, too -- it is neccessary for
> software suspend.
>
> Signed-off-by: Pavel Machek <[email protected]>
>
> ---
> commit 2206dab43d50723d6b15caa8821e8d97c6b5ef28
> tree cbfc324e15d216aa91ce6a51927668076de5b7db
> parent dd76aabd03933b80c61fa5b0c0c995950246c603
> author <[email protected]> Thu, 30 Mar 2006 00:06:31 +0200
> committer <[email protected]> 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?
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