linux-kernel - Re: [PATCH 1/3] cpuidle: If disable_cpuidle() is called, set pm_idle to default

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Date:	Wed, 09 Nov 2011 15:49:49 +0530
From:	Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	linux-kernel@...r.kernel.org, x86@...nel.org, len.brown@...el.com,
	tglx@...utronix.de, jeremy@...p.org, hpa@...or.com, bp@...en8.de,
	tj@...nel.org, trenn@...e.de, mingo@...hat.com,
	xen-devel@...ts.xensource.com, stable@...nel.org
Subject: Re: [PATCH 1/3] cpuidle: If disable_cpuidle() is called, set pm_idle
 to default_idle.

On Wednesday 09 November 2011 02:45 AM, Konrad Rzeszutek Wilk wrote:
> . however we ignore the disable_cpuidle() directive and
> in select_idle_routine() set it to type preferred by the CPU.
> 
> This is a regression introduced by
> 
>  commit a0bfa1373859e9d11dc92561a8667588803e42d8
>  Author: Len Brown <len.brown@...el.com>
>  Date:   Fri Apr 1 19:34:59 2011 -0400
> 
>      cpuidle: stop depending on pm_idle
> 
> specifically 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.
> 
> .. but the default HLT does not get used. Instead we end up in the
> situation that select_idle_routine() is called from arch/x86/kernel/cpu/common.c
> and if we called cpuidle_disable(), then the pm_idle is not set, and
> we end up setting pm_idle to mwait_idle or amd_e400_idle.
> 
> This patch uses the cpuidle_disabled() functionality and
> makes select_idle_routine() adhere to that.
> 
> Reported-by: Stefan Bader <stefan.bader@...onical.com>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> 
> CC: Thomas Gleixner <tglx@...utronix.de>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: "H. Peter Anvin" <hpa@...or.com>
> CC: x86@...nel.org
> CC: Len Brown <len.brown@...el.com>
> CC: Borislav Petkov <bp@...en8.de>
> CC: Tejun Heo <tj@...nel.org>
> CC: Thomas Renninger <trenn@...e.de>
> CC: stable@...nel.org
> ---
>  arch/x86/kernel/process.c |    5 +++++
>  include/linux/cpuidle.h   |    2 ++
>  2 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index e7e3b01..1f7f8c8 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -14,6 +14,7 @@
>  #include <linux/utsname.h>
>  #include <trace/events/power.h>
>  #include <linux/hw_breakpoint.h>
> +#include <linux/cpuidle.h>
>  #include <asm/cpu.h>
>  #include <asm/system.h>
>  #include <asm/apic.h>
> @@ -587,6 +588,10 @@ void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
>  	if (pm_idle)
>  		return;
> 
> +	if (cpuidle_disabled()) {
> +		pm_idle = default_idle;
> +		return;
> +	}


The above check is needed to initialise pm_idle to default_idle if
cpuidle is disabled but this requirement here is Zen specific. 
On other architectures, if cpuidle is disabled on boot then we 
rather would want mwait_idle or amd_e400_idle to be enabled than 
default_idle. Can we make this check Zen specific ? 

...  if(ZEN_ARCH && cpuidle_disabled()) ... 




>  	if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
>  		/*
>  		 * One CPU supports mwait => All CPUs supports mwait
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index b51629e..123fe9e 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -122,6 +122,7 @@ struct cpuidle_driver {
>  };
> 
>  #ifdef CONFIG_CPU_IDLE
> +extern int cpuidle_disabled(void);
>  extern void disable_cpuidle(void);
>  extern int cpuidle_idle_call(void);
> 
> @@ -137,6 +138,7 @@ extern int cpuidle_enable_device(struct cpuidle_device *dev);
>  extern void cpuidle_disable_device(struct cpuidle_device *dev);
> 
>  #else
> +static inline int cpuidle_disabled(void) { return 1; }
>  static inline void disable_cpuidle(void) { }
>  static inline int cpuidle_idle_call(void) { return -ENODEV; }
> 

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