Re: (fwd) empty /sys/power/state?

Stefan Richter
2007-05-19T23:33:16Z

Rafael J. Wysocki wrote:
> We use the CPU hotplug code for disabling/enabling nonboot CPUs.
>
> You need to enable it to be able to suspend (BTW, it's also necesary for
> the suspend to RAM).

I now noticed that this is documented in the help text of i386's
Kconfig. But it is not mentioned in the help text of x86_64's Kconfig.
Also, I think that should already be shown in the prompt, not just in
the help text.

From: Stefan Richter <stefanr@s5r6.in-berlin.de>
Subject: i386, x86-64: show that CONFIG_HOTPLUG_CPU is required for suspend on SMP

Point out the non-obvious.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
---
arch/i386/Kconfig | 2 +-
arch/x86_64/Kconfig | 7 +++++--
2 files changed, 6 insertions(+), 3 deletions(-)

Index: linux/arch/i386/Kconfig
===================================================================
--- linux.orig/arch/i386/Kconfig
+++ linux/arch/i386/Kconfig
@@ -891,7 +891,7 @@ config PHYSICAL_ALIGN
Don't change this unless you know what you are doing.

config HOTPLUG_CPU
- bool "Support for hot-pluggable CPUs (EXPERIMENTAL)"
+ bool "Support for suspend on SMP hot-pluggable CPUs (EXPERIMENTAL)"
depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER
---help---
Say Y here to experiment with turning CPUs off and on, and to
Index: linux/arch/x86_64/Kconfig
===================================================================
--- linux.orig/arch/x86_64/Kconfig
+++ linux/arch/x86_64/Kconfig
@@ -428,12 +428,15 @@ config NR_CPUS
memory in the static kernel configuration.

config HOTPLUG_CPU
- bool "Support for hot-pluggable CPUs (EXPERIMENTAL)"
+ bool "Support for suspend on SMP and hot-pluggable CPUs (EXPERIMENTAL)"
depends on SMP && HOTPLUG && EXPERIMENTAL
help
Say Y here to experiment with turning CPUs off and on. CPUs
can be controlled through /sys/devices/system/cpu/cpu#.
- Say N if you want to disable CPU hotplug.
+ This is also required for suspend on SMP systems.
+
+ Say N if you want to disable CPU hotplug and don't need to
+ suspend.

config ARCH_ENABLE_MEMORY_HOTPLUG
def_bool y

--
Stefan Richter
-=====-=-=== -=-= =-=--