Re: [patch 05/40] cpu: Restructure cpu_down code

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Thu, Jan 31, 2013 at 12:11:15PM -0000, Thomas Gleixner wrote:
> Split out into separate functions, so we can convert it to a state machine.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> ---
>  kernel/cpu.c |   69 ++++++++++++++++++++++++++++++++++++++++-------------------
>  1 file changed, 47 insertions(+), 22 deletions(-)
> 
> Index: linux-2.6/kernel/cpu.c
> ===================================================================
> --- linux-2.6.orig/kernel/cpu.c
> +++ linux-2.6/kernel/cpu.c
> @@ -168,6 +168,43 @@ static int cpu_notify(unsigned long val,
>  	return __cpu_notify(val, cpu, -1, NULL);
>  }
> 
> +/* Notifier wrappers for transitioning to state machine */
> +static int notify_prepare(unsigned int cpu)
> +{
> +	int nr_calls = 0;
> +	int ret;
> +
> +	ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
> +	if (ret) {
> +		nr_calls--;
> +		printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
> +				__func__, cpu);
> +		__cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
> +	}
> +	return ret;
> +}
> +
> +static int notify_online(unsigned int cpu)
> +{
> +	cpu_notify(CPU_ONLINE, cpu);
> +	return 0;
> +}
> +
> +static int bringup_cpu(unsigned int cpu)
> +{
> +	struct task_struct *idle = idle_thread_get(cpu);
> +	int ret;
> +
> +	/* Arch-specific enabling code. */
> +	ret = __cpu_up(cpu, idle);
> +	if (ret) {
> +		cpu_notify(CPU_UP_CANCELED, cpu);
> +		return ret;
> +	}
> +	BUG_ON(!cpu_online(cpu));
> +	return 0;
> +}
> +
>  #ifdef CONFIG_HOTPLUG_CPU
> 
>  static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
> @@ -340,7 +377,7 @@ EXPORT_SYMBOL(cpu_down);
>  static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
>  {
>  	struct task_struct *idle;
> -	int ret, nr_calls = 0;
> +	int ret;
> 
>  	cpu_hotplug_begin();
> 
> @@ -355,35 +392,23 @@ static int __cpuinit _cpu_up(unsigned in
>  		goto out;
>  	}
> 
> +	cpuhp_tasks_frozen = tasks_frozen;
> +
>  	ret = smpboot_create_threads(cpu);
>  	if (ret)
>  		goto out;
> 
> -	cpuhp_tasks_frozen = tasks_frozen;
> -
> -	ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
> -	if (ret) {
> -		nr_calls--;
> -		printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
> -				__func__, cpu);
> -		goto out_notify;
> -	}
> +	ret = notify_prepare(cpu);
> +	if (ret)
> +		goto out;
> 
> -	/* Arch-specific enabling code. */
> -	ret = __cpu_up(cpu, idle);
> -	if (ret != 0)
> -		goto out_notify;
> -	BUG_ON(!cpu_online(cpu));
> +	ret = bringup_cpu(cpu);
> +	if (ret)
> +		goto out;
> 
>  	/* Wake the per cpu threads */
>  	smpboot_unpark_threads(cpu);
> -
> -	/* Now call notifier in preparation. */
> -	cpu_notify(CPU_ONLINE, cpu);
> -
> -out_notify:
> -	if (ret != 0)
> -		__cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
> +	notify_online(cpu);
>  out:
>  	cpu_hotplug_done();
> 
> 
>