linux-kernel - Re: [2.6 patch] let SUSPEND select HOTPLUG

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Message-Id: <200707282030.44484.rjw@sisk.pl>
Date:	Sat, 28 Jul 2007 20:30:43 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Adrian Bunk <bunk@...sta.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>, david@...g.hm,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Pavel Machek <pavel@....cz>
Subject: Re: [2.6 patch] let SUSPEND select HOTPLUG_CPU

On Saturday, 28 July 2007 00:25, Adrian Bunk wrote:
> On Thu, Jul 26, 2007 at 01:55:18PM -0700, Linus Torvalds wrote:
> > 
> > 
> > On Thu, 26 Jul 2007, Rafael J. Wysocki wrote:
> > > 
> > > My point is we have ACPI dependent on PM, so if you want ACPI, you end
> > > up with all of the STR stuff built in, which is what you don't like (if I
> > > understand that correctly).  If we have CONFIG_SUSPEND, you'll be able to
> > > choose ACPI alone. :-)
> > 
> > Good point. 
> > 
> > Anyway, I think the ACPI problem really is as trivial as the following 
> > three-liner removal fix. If the user doesn't want suspend, ACPI shouldn't 
> > force it on him.
> > 
> > A nicer fix might be to also make some of the ACPI helper routines depend 
> > on whether they are needed or not (which in turn will depend on whether 
> > suspend support has been compiled into the kernel), but quite frankly, 
> > that's secondary at least for me.
> > 
> > So if we have a few ACPI routines that will never get called (because we 
> > don't even enable the interfaces that would *cause* them to be called), I 
> > don't think that's a huge problem. It's a beauty wart, but nobody really 
> > cares (and it's even something that we could get the compiler to optimize 
> > away for us if we really cared).
> > 
> > 		Linus
> > 
> > ---
> >     Don't force-enable suspend/hibernate support just for ACPI
> >     
> >     It's a totally independent decision for the user whether he wants
> >     suspend and/or hibernation support, and ACPI shouldn't care.
> >     
> >     Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > ---
> >  drivers/acpi/Kconfig |    3 ---
> >  1 files changed, 0 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> > index 251344c..22b401b 100644
> > --- a/drivers/acpi/Kconfig
> > +++ b/drivers/acpi/Kconfig
> > @@ -11,9 +11,6 @@ menuconfig ACPI
> >  	depends on PCI
> >  	depends on PM
> >  	select PNP
> > -	# for sleep
> > -	select HOTPLUG_CPU if X86 && SMP
> > -	select SUSPEND_SMP if X86 && SMP
> >  	default y
> >  	---help---
> >  	  Advanced Configuration and Power Interface (ACPI) support for 
> 
> The dependency of SUSPEND_SMP on HOTPLUG_CPU is quite unintuitive, so 
> what about something like the patch below?
> 
> This should address a main issue behind Len's patch.
> 
> 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 changes SOFTWARE_SUSPEND if SMP to select HOTPLUG_CPU instead 
> of depending on it.
> 
> Signed-off-by: Adrian Bunk <bunk@...sta.de>
> 
> ---
> 
>  kernel/power/Kconfig |   20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -72,9 +72,22 @@ 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_SMP_POSSIBLE
> +	bool
> +	depends on (X86 && !X86_VOYAGER) || (PPC64 && (PPC_PSERIES || PPC_PMAC))
> +	depends on SMP
> +	default y
> +
> +config SUSPEND_SMP
> +	bool
> +	depends on SUSPEND_SMP_POSSIBLE && SOFTWARE_SUSPEND
> +	select HOTPLUG_CPU
> +	default y

That should not depend on SOFTWARE_SUSPEND (it's equivalent to HIBERNATION).

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth
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