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Subject[2.6 patch] SOFTWARE_SUSPEND: handle HOTPLUG_CPU automatically
On Fri, Jul 27, 2007 at 03:57:39PM -0700, Linus Torvalds wrote:
>
>
> On Sat, 28 Jul 2007, Adrian Bunk wrote:
> >
> > The dependency of SUSPEND_SMP on HOTPLUG_CPU is quite unintuitive, so
> > what about something like the patch below?
>
> Yeah, this looks reasonable.
>
> May I suggest another level of indirection, though:
>
> > +config SUSPEND_SMP_POSSIBLE
> > + bool
> > + depends on (X86 && !X86_VOYAGER) || (PPC64 && (PPC_PSERIES || PPC_PMAC))
> > + depends on SMP
> > + default y
>
> How about making this a bit more split up, and do it as
>
> # SMP suspend is possible on ..
> config SUSPEND_SMP_POSSIBLE
> bool
> depends on (X86 && !X86_VOYAGER) || (PPC64 && (PPC_PSERIES || PPC_PMAC))
> default y
>
> # UP suspend is possible on ..
> config SUSPEND_UP_POSSIBLE
> bool
> depends on X86 || PPC64_SWSUSP || FRV || PPC32
> default y

Sounds good.

> # Can we suspend?
> config SUSPEND_POSSIBLE
> bool
> depends on (SMP && SUSPEND_SMP_POSSIBLE) || (SUSPEND_UP_POSSIBLE && !SMP)
> default y

IMHO not required:

config SOFTWARE_SUSPEND
bool "Software Suspend (Hibernation)"
depends on PM && SWAP
depends on SUSPEND_UP_POSSIBLE || SUSPEND_SMP_POSSIBLE

> and then we have just a
>
> config SOFTWARE_SUSPEND
> bool "Software Suspend (Hibernation)"
> depends on PM && SWAP
> depends on SUSPEND_POSSIBLE
>
> config SUSPEND_SMP
> bool
> depends on SOFTWARE_SUSPEND && SMP
> select HOTPLUG_CPU
> default y
>
> and now each of the config options looks pretty simple and describe one
> thing.
>
> [ For extra bonus points: the SUSPEND_POSSIBLE thing is still pretty
> complicated, and it might actually be a better idea to make it a
> per-arch config option, and just make the x86/arch say
>
> config SUSPEND_POSSIBLE
> bool
> depends on !(X86_VOYAGER && SMP)
> default y

This would give you "trying to assign nonexistent symbol SUSPEND_POSSIBLE"
kconfig warnings on architectures without SUSPEND_POSSIBLE.

(And you missed the UP case in your example.)

> instead: since SUSPEND_POSSIBLE is always true on x86 regardless of SMP
> or not, just not on X86_VOYAGER. Then, each architecture can have its
> own private rules for whether that architecture has SUSPEND_POSSIBLE or
> not, so on ppc, it might look like
>
> config SUSPEND_POSSIBLE
> bool
> depends on (PPC64 && (PPC_PSERIES || PPC_PMAC)) || PPC_SWSUSP
> bool y
>
> or something, but the point is, now the complexity is a per-architecture
> thing, so other architectures simply don't have to care any more! ]
>
> And the user only ever sees one single question: the one for
> "SOFTWARE_SUSPEND". All the others would directly flow either from the
> architecture choice, or from that.
>
> Anybody willing to rewrite it that way?

Patch below.

> Linus

cu
Adrian


<-- snip -->


An implementation detail of the suspend code that is not intuitive for
the user is the HOTPLUG_CPU dependency of SOFTWARE_SUSPEND if SMP.

This patch handles the dependency of SOFTWARE_SUSPEND on HOTPLUG_CPU
automatically without the user requiring to know about it.

Thanks to Stefan Richter and Linus Torvalds for valuable feedback.

Signed-off-by: Adrian Bunk <bunk@stusta.de>

---

arch/i386/Kconfig | 16 +++++++++++-----
arch/powerpc/Kconfig | 11 +++++++++--
arch/x86_64/Kconfig | 19 ++++++++++++-------
kernel/power/Kconfig | 23 +++++++++++++++++------
4 files changed, 49 insertions(+), 20 deletions(-)

commit bb14e6721dc4e1a97efbfa5398d6021b321af52d
Author: Adrian Bunk <bunk@stusta.de>
Date: Sat Jul 28 06:47:03 2007 +0200

asdf

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index abb582b..eb00a12 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -903,13 +903,19 @@ config PHYSICAL_ALIGN

Don't change this unless you know what you are doing.

-config HOTPLUG_CPU
- bool "Support for suspend on SMP and hot-pluggable CPUs (EXPERIMENTAL)"
+config HOTPLUG_CPU_POSSIBLE
+ bool
depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER
+ select SUSPEND_SMP_POSSIBLE
+ default y
+
+config HOTPLUG_CPU
+ bool "Support for hot-pluggable CPUs (EXPERIMENTAL)" if !SUSPEND_SMP
+ depends on HOTPLUG_CPU_POSSIBLE
+ default y if SUSPEND_SMP
---help---
- 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 Y here to experiment with turning CPUs off and on.
+ CPUs can be controlled through /sys/devices/system/cpu.

config COMPAT_VDSO
bool "Compat VDSO support"
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 00099ef..950be0b 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -192,9 +192,16 @@ config IOMMU_VMERGE
from *_map_sg(). Say Y if you know the drivers you are using are
properly handling this case.

-config HOTPLUG_CPU
- bool "Support for enabling/disabling CPUs"
+config HOTPLUG_CPU_POSSIBLE
+ bool
depends on SMP && HOTPLUG && EXPERIMENTAL && (PPC_PSERIES || PPC_PMAC)
+ select SUSPEND_SMP_POSSIBLE if PPC64
+ default y
+
+config HOTPLUG_CPU
+ bool "Support for enabling/disabling CPUs (EXPERIMENTAL)" if !SUSPEND_SMP
+ depends on HOTPLUG_CPU_POSSIBLE
+ default y if SUSPEND_SMP
---help---
Say Y here to be able to disable and re-enable individual
CPUs at runtime on SMP machines.
diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 45f82ae..810ed4b 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -443,16 +443,21 @@ config PHYSICAL_ALIGN
hex
default "0x200000"

-config HOTPLUG_CPU
- bool "Support for suspend on SMP and hot-pluggable CPUs (EXPERIMENTAL)"
+config HOTPLUG_CPU_POSSIBLE
+ bool
depends on SMP && HOTPLUG && EXPERIMENTAL
+ select SUSPEND_SMP_POSSIBLE
+ default y
+
+config HOTPLUG_CPU
+ bool "Support for hot-pluggable CPUs (EXPERIMENTAL)" if !SUSPEND_SMP
+ depends on HOTPLUG_CPU_POSSIBLE
+ default y if SUSPEND_SMP
help
- Say Y here to experiment with turning CPUs off and on. CPUs
- can be controlled through /sys/devices/system/cpu/cpu#.
- This is also required for suspend/hibernation on SMP systems.
+ 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 and don't need to
- suspend.
+ If unsure, say N.

config ARCH_ENABLE_MEMORY_HOTPLUG
def_bool y
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index c1a106d..c7f74ba 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -72,9 +72,25 @@ config PM_TRACE
CAUTION: this option will cause your machine's real-time clock to be
set to an invalid time after a resume.

+config SUSPEND_UP_POSSIBLE
+ bool
+ depends on FRV || PPC32 || PPC64_SWSUSP || X86
+ depends on !SMP
+ default y
+
+# select'ed from arch/<arch>/Kconfig if supported
+config SUSPEND_SMP_POSSIBLE
+ bool
+
+config SUSPEND_SMP
+ bool
+ depends on SUSPEND_SMP_POSSIBLE && SOFTWARE_SUSPEND
+ default y
+
config SOFTWARE_SUSPEND
bool "Software Suspend (Hibernation)"
- depends on PM && SWAP && (((X86 || PPC64_SWSUSP) && (!SMP || SUSPEND_SMP)) || ((FRV || PPC32) && !SMP))
+ depends on PM && SWAP
+ depends on SUSPEND_UP_POSSIBLE || SUSPEND_SMP_POSSIBLE
---help---
Enable the suspend to disk (STD) functionality, which is usually
called "hibernation" in user interfaces. STD checkpoints the
@@ -132,11 +148,6 @@ config PM_STD_PARTITION
suspended image to. It will simply pick the first available swap
device.

-config SUSPEND_SMP
- bool
- depends on HOTPLUG_CPU && (X86 || PPC64) && PM
- default y
-
config APM_EMULATION
tristate "Advanced Power Management Emulation"
depends on PM && SYS_SUPPORTS_APM_EMULATION
-
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