linux-kernel - Re: 3.2-rc2+: Reported regressions from 3.0 and 3.1

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Date:	Tue, 29 Nov 2011 15:08:15 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Borislav Petkov <bp@...64.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, x86@...nel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux SCSI List <linux-scsi@...r.kernel.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	Linux Wireless List <linux-wireless@...r.kernel.org>,
	DRI <dri-devel@...ts.freedesktop.org>,
	Florian Mickler <florian@...kler.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux PM List <linux-pm@...ts.linux-foundation.org>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	deepthi@...ux.vnet.ibm.com
Subject: Re: 3.2-rc2+: Reported regressions from 3.0 and 3.1

On Tue, Nov 29, 2011 at 07:34:28PM +0100, Borislav Petkov wrote:
> On Tue, Nov 29, 2011 at 01:04:14PM -0500, Konrad Rzeszutek Wilk wrote:
> > This patch:
> > 
> > commit d91ee5863b71e8c90eaf6035bff3078a85e2e7b5
> > Author: Len Brown <len.brown@...el.com>
> > Date:   Fri Apr 1 18:28:35 2011 -0400
> > 
> >     cpuidle: replace xen access to x86 pm_idle and default_idle
> > 
> >     ..scribble on pm_idle and access default_idle,
> >    have it simply disable_cpuidle() so acpi_idle will not load and
> >    architecture default HLT will be used.
> > 
> > idea was to have one call - disable_cpuidle() which would make
> > pm_idle not be molested by other code. It disallows cpuidle_idle_call
> > and acpi_idle_call to not set pm_idle (which is excellent). But the
> 
> what is acpi_idle_call, I can't find it anywhere.

You are right. I had "acpi_idle_enter_*" and its friend in mind. Which
are called from the cpuidle_idle_call.

Let me fix that comment up.
> 
> > amd_e400_idle and mwait_idle can still setup pm_idle which we really
> > do not want.
> 
> This is not the case: rather select_idle_routine()/idle_setup() sets
> pm_idle.

Yes. Let me fix up the comment.
> 
> [..]
> 
> > +bool set_pm_idle_to_default()
> > +{
> > +	if (!pm_idle) {
> > +		pm_idle = default_idle;
> > +		return true;
> > +	}
> > +	return false;
> > +}
> 
> I don't understand what you're trying to achieve here? Do you want
> default_idle to be always the pm_idle for xen or what is the deal here?

Yes (always want default_idle).
> 
> If yes, then simply do:
> 
> bool set_pm_idle_to_default(void)	// remember to add "void" for no function args
> {
> 	bool ret = !!pm_idle;
> 
> 	pm_idle = default_idle;

That would work too.
> 
> 	return ret;
> 
> }
> 
> ...
> 
> >  void stop_this_cpu(void *dummy) 
> >  {
> >  	local_irq_disable();
> > diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> > index 46d6d21..7506181 100644
> > --- a/arch/x86/xen/setup.c
> > +++ b/arch/x86/xen/setup.c
> > @@ -448,6 +448,6 @@ void __init xen_arch_setup(void)
> >  #endif
> >  	disable_cpuidle();
> >  	boot_option_idle_override = IDLE_HALT;
> > -
> > +	WARN_ON(!set_pm_idle_to_default());
> 
> and then do
> 
> 	WARN_ON(set_pm_idle_to_default());
> 
> instead of having arbitrary confusing logic. This way you can warn
> whether something else set pm_idle already. Or?

That would work as well.
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