Subject: Re: FAILED: patch "[PATCH] powerpc/pseries: Always enable CONFIG_HOTPLUG_CPU on PSERIES" failed to apply to 3.9-stable tree

From: "Srivatsa S. Bhat" <[email-masked]>
Date: Mon, 03 Jun 2013 12:16:35 +0530

On 06/02/2013 03:15 AM, [email-masked] wrote:
> 
> The patch below does not apply to the 3.9-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <[email-masked]>.
> 

Please find the 3.9 backport below. Thank you!

Regards,
Srivatsa S. Bhat

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From: Srivatsa S. Bhat <[email-masked]>
Subject: [PATCH] powerpc/pseries: Always enable CONFIG_HOTPLUG_CPU on PSERIES SMP

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 ‘rtas_cpu_state_change_mask’:
arch/powerpc/kernel/rtas.c:843:4: error: implicit declaration of function ‘cpu_down’ [-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 <[email-masked]>
Cc: [email-masked]
Signed-off-by: Srivatsa S. Bhat <[email-masked]>
Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
---

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

diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
index 9a0941b..b9fd0d3 100644
--- 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