Patch "powerpc/pseries: Always enable CONFIG_HOTPLUG_CPU on PSERIES SMP" has been added to the 3.9-stable tree

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This is a note to let you know that I've just added the patch titled

    powerpc/pseries: Always enable CONFIG_HOTPLUG_CPU on PSERIES SMP

to the 3.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     powerpc-pseries-always-enable-config_hotplug_cpu-on-pseries-smp.patch
and it can be found in the queue-3.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From f274ef8747d3be649bba8708696fb31cb00fa75a Mon Sep 17 00:00:00 2001
From: "Srivatsa S. Bhat" <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Date: Tue, 21 May 2013 09:32:48 +0000
Subject: powerpc/pseries: Always enable CONFIG_HOTPLUG_CPU on PSERIES SMP

From: "Srivatsa S. Bhat" <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>

commit f274ef8747d3be649bba8708696fb31cb00fa75a upstream.

Adam Lackorzynski reported the following build failure on
!CONFIG_HOTPLUG_CPU configuration:

  CC      arch/powerpc/kernel/rtas.o
arch/powerpc/kernel/rtas.c: In function â??rtas_cpu_state_change_maskâ??:
arch/powerpc/kernel/rtas.c:843:4: error: implicit declaration of function â??cpu_downâ?? [-Werror=implicit-function-declaration]
cc1: all warnings being treated as errors
make[1]: *** [arch/powerpc/kernel/rtas.o] Error 1
make: *** [arch/powerpc/kernel] Error 2

The build fails because cpu_down() is defined only under CONFIG_HOTPLUG_CPU.

Looking further, the mobility code in pseries is one of the call-sites which
uses rtas_ibm_suspend_me(), which in turn calls rtas_cpu_state_change_mask().
And the mobility code is unconditionally compiled-in (it does not fall under
any Kconfig option). And commit 120496ac (powerpc: Bring all threads online
prior to migration/hibernation) which introduced this build regression is
critical for the proper functioning of the migration code. So it appears
that the only solution to this problem is to enable CONFIG_HOTPLUG_CPU if
SMP is enabled on PPC_PSERIES platforms. So make that change in the Kconfig.

Reported-by: Adam Lackorzynski <adam@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/powerpc/platforms/pseries/Kconfig |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/powerpc/platforms/pseries/Kconfig
+++ b/arch/powerpc/platforms/pseries/Kconfig
@@ -18,6 +18,8 @@ config PPC_PSERIES
 	select PPC_PCI_CHOICE if EXPERT
 	select ZLIB_DEFLATE
 	select PPC_DOORBELL
+	select HOTPLUG if SMP
+	select HOTPLUG_CPU if SMP
 	default y
 
 config PPC_SPLPAR


Patches currently in stable-queue which might be from srivatsa.bhat@xxxxxxxxxxxxxxxxxx are

queue-3.9/powerpc-pseries-always-enable-config_hotplug_cpu-on-pseries-smp.patch
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