linux-kernel - Re: [RFC PATCH 1/4] Refcount Based Cpu-Hotplug Implementation

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Date:	Wed, 17 Oct 2007 17:20:47 +0530
From:	Gautham R Shenoy <ego@...ibm.com>
To:	Paul Jackson <pj@....com>
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, vatsa@...ibm.com,
	rusty@...tcorp.com.au, dipankar@...ibm.com, oleg@...sign.ru,
	mingo@...e.hu, paulmck@...ibm.com
Subject: Re: [RFC PATCH 1/4] Refcount Based Cpu-Hotplug Implementation

Hi Paul,

On Wed, Oct 17, 2007 at 04:27:09AM -0700, Paul Jackson wrote:
> With the following patch, the four cpu hotplug patches by
> Gautham R Shenoy boot successfully on my sn2_defconfig ia64
> SN2 Altix system.
> 
> This patch moves the cpu_hotplug_init() code outside of the
> #ifdef CONFIG_HOTPLUG_CPU code.
> 
> I will confess to being confused however as to the best way
> to handle this.  Having "cpu_hotplug_init" be a piece of code
> that has to execute whether or not CONFIG_HOTPLUG_CPU is
> enabled doesn't seem right.

Thanks for the patch! 

I had not tested the patch series with !CONFIG_HOTPLUG_CPU,
so no wonder I missed it.

> 
> Signed-off-by: Paul Jackson <pj@....com>
> 

Acked-by: Gautham R Shenoy <ego@...ibm.com>

> ---
> 
>  include/linux/cpu.h |    3 +--
>  kernel/cpu.c        |    4 ++--
>  2 files changed, 3 insertions(+), 4 deletions(-)
> 
> --- 2.6.23-mm1.orig/include/linux/cpu.h	2007-10-17 03:59:59.529623639 -0700
> +++ 2.6.23-mm1/include/linux/cpu.h	2007-10-17 04:03:56.257223754 -0700
> @@ -83,6 +83,7 @@ static inline void unregister_cpu_notifi
> 
>  #endif /* CONFIG_SMP */
>  extern struct sysdev_class cpu_sysdev_class;
> +extern void cpu_hotplug_init(void);
> 
>  #ifdef CONFIG_HOTPLUG_CPU
>  /* Stop CPUs going up and down. */
> @@ -97,7 +98,6 @@ static inline void cpuhotplug_mutex_unlo
>  	mutex_unlock(cpu_hp_mutex);
>  }
> 
> -extern void cpu_hotplug_init(void);
>  extern void get_online_cpus(void);
>  extern void put_online_cpus(void);
>  #define hotcpu_notifier(fn, pri) {				\
> @@ -117,7 +117,6 @@ static inline void cpuhotplug_mutex_lock
>  static inline void cpuhotplug_mutex_unlock(struct mutex *cpu_hp_mutex)
>  { }
> 
> -#define cpu_hotplug_init()		do { } while (0)
>  #define get_online_cpus()		do { } while (0)
>  #define put_online_cpus()		do { } while (0)
>  #define hotcpu_notifier(fn, pri)	do { (void)(fn); } while (0)
> --- 2.6.23-mm1.orig/kernel/cpu.c	2007-10-17 03:59:59.873628872 -0700
> +++ 2.6.23-mm1/kernel/cpu.c	2007-10-17 04:04:52.522079165 -0700
> @@ -38,8 +38,6 @@ static struct {
> 
>  #define writer_exists() (cpu_hotplug.active_writer != NULL)
> 
> -#ifdef CONFIG_HOTPLUG_CPU
> -
>  void __init cpu_hotplug_init(void)
>  {
>  	cpu_hotplug.active_writer = NULL;
> @@ -48,6 +46,8 @@ void __init cpu_hotplug_init(void)
>  	init_completion(&cpu_hotplug.readers_done);
>  }
> 
> +#ifdef CONFIG_HOTPLUG_CPU
> +
>  void get_online_cpus(void)
>  {
>  	might_sleep();
> 
> 
> -- 
>                   I won't rest till it's the best ...
>                   Programmer, Linux Scalability
>                   Paul Jackson <pj@....com> 1.925.600.0401

-- 
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
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