linux-kernel - Re: [PATCH 12/16] cpuidle: coupled: Convert to hotplug state machine

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Date:   Tue, 23 Aug 2016 16:24:52 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, rt@...utronix.de,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org
Subject: Re: [PATCH 12/16] cpuidle: coupled: Convert to hotplug state machine

On 08/18/2016 02:57 PM, Sebastian Andrzej Siewior wrote:
> Install the callbacks via the state machine.
> 
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Cc: linux-pm@...r.kernel.org
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---

[ ... ]

> -
>  	mutex_lock(&cpuidle_lock);
>  
>  	dev = per_cpu(cpuidle_devices, cpu);
>  	if (!dev || !dev->coupled)
>  		goto out;
>  
> -	switch (action & ~CPU_TASKS_FROZEN) {
> -	case CPU_UP_PREPARE:
> -	case CPU_DOWN_PREPARE:
> -		cpuidle_coupled_prevent_idle(dev->coupled);
> -		break;
> -	case CPU_ONLINE:
> -	case CPU_DEAD:
> -		cpuidle_coupled_update_online_cpus(dev->coupled);
> -		/* Fall through */
> -	case CPU_UP_CANCELED:
> -	case CPU_DOWN_FAILED:
> -		cpuidle_coupled_allow_idle(dev->coupled);
> -		break;
> -	}
> -
> +	cpuidle_coupled_update_online_cpus(dev->coupled);
> +	cpuidle_coupled_allow_idle(dev->coupled);
>  out:
>  	mutex_unlock(&cpuidle_lock);
> -	return NOTIFY_OK;
> +	return 0;

You can remove the useless label 'out':

if (dev && dev->coupled) {
	cpuidle_coupled_update_online_cpus(dev->coupled);
	cpuidle_coupled_allow_idle(dev->coupled);
}

>  }
>  
> -static struct notifier_block cpuidle_coupled_cpu_notifier = {
> -	.notifier_call = cpuidle_coupled_cpu_notify,
> -};
> +static int coupled_cpu_up_prepare(unsigned int cpu)
> +{
> +	struct cpuidle_device *dev;
> +
> +	mutex_lock(&cpuidle_lock);
> +
> +	dev = per_cpu(cpuidle_devices, cpu);
> +	if (!dev || !dev->coupled)
> +		goto out;
> +
> +	cpuidle_coupled_prevent_idle(dev->coupled);
> +out:
> +	mutex_unlock(&cpuidle_lock);
> +	return 0;

Same comment here.

> +}
>  
>  static int __init cpuidle_coupled_init(void)
>  {
> -	return register_cpu_notifier(&cpuidle_coupled_cpu_notifier);
> +	int ret;
> +
> +	ret = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_COUPLED_PREPARE,
> +					"CPUIDLE_COUPLED_PREPARE",
> +					coupled_cpu_up_prepare,
> +					coupled_cpu_online);
> +	if (ret)
> +		goto err;

There is nothing to undo here.

	if (ret)
		return ret;

> +	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
> +					"CPUIDLE_COUPLED_ONLINE",
> +					coupled_cpu_online,
> +					coupled_cpu_up_prepare);
> +	if (ret < 0)
> +		goto err;

	if (ret)
		cpuhp_remove_state_nocalls(
			CPUHP_CPUIDLE_COUPLED_PREPARE);
		
	return ret;

> +	return 0;
> +err:
> +	cpuhp_remove_state_nocalls(CPUHP_CPUIDLE_COUPLED_PREPARE);
> +	return ret;

  ^^^^^ zaaap !



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