Re: [PATCH 1/2] cpuidle: add hotplug support to initialize the timer broadcast

[Daniel Lezcano <daniel.lezcano@linaro.org>]

On 07/30/2013 03:54 PM, Daniel Lezcano wrote:
> Commit 89878baa73f0f1c679355006bd8632e5d78f96c2 introduced the flag
> CPUIDLE_FLAG_TIMER_STOP where we specify a specific idle state stops the local
> timer.
> 
> Commit a06df062a189a8d5588babb8bf0bb78672497798 introduced the initialization
> of the timer broadcast framework depending of the flag presence.
> 
> If a system is booted with some cpus offline, by setting for example, maxcpus=1
> in the kernel command line, and then they are set online, the timer broadcast
> won't be setup automatically.
> 
> Fix this by adding the cpu hotplug notifier and enable/disable the timer
> broadcast automatically. So no need to handle that at the arch specific driver
> level like eg. intel_idle does.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> ---

Len, Rafael,

any comment on these two patches ?

Thanks
  -- Daniel


>  drivers/cpuidle/driver.c |   48 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 48 insertions(+)
> 
> diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
> index 3ac499d..e976994 100644
> --- a/drivers/cpuidle/driver.c
> +++ b/drivers/cpuidle/driver.c
> @@ -10,6 +10,7 @@
>  
>  #include <linux/mutex.h>
>  #include <linux/module.h>
> +#include <linux/cpu.h>
>  #include <linux/cpuidle.h>
>  #include <linux/cpumask.h>
>  #include <linux/clockchips.h>
> @@ -147,6 +148,48 @@ static void cpuidle_setup_broadcast_timer(void *arg)
>  }
>  
>  /**
> + * cpuidle_hotplug_notify: notifier callback when a cpu is onlined/offlined
> + * @n: the notifier block
> + * @action: an unsigned long giving the event related to the notification
> + * @hcpu: a void pointer but used as the cpu number which the event is related
> + *
> + * The kernel can boot with some cpus offline, we have to init the timer
> + * broadcast for these cpus when they are onlined. Also we have to disable
> + * the timer broadcast when the cpu is down.
> + *
> + * Returns NOTIFY_OK
> + */
> +static int cpuidle_hotplug_notify(struct notifier_block *n,
> +				  unsigned long action, void *hcpu)
> +{
> +	int cpu = (unsigned long)hcpu;
> +	struct cpuidle_driver *drv;
> +
> +	drv = __cpuidle_get_cpu_driver(cpu);
> +	if (!drv || !drv->bctimer)
> +		goto out;
> +
> +	switch (action & 0xf) {
> +	case CPU_ONLINE:
> +		smp_call_function_single(cpu, cpuidle_setup_broadcast_timer,
> +					 (void *)CLOCK_EVT_NOTIFY_BROADCAST_ON,
> +					 1);
> +		break;
> +	case CPU_DEAD:
> +		smp_call_function_single(cpu, cpuidle_setup_broadcast_timer,
> +					 (void *)CLOCK_EVT_NOTIFY_BROADCAST_OFF,
> +					 1);
> +		break;
> +	}
> +out:
> +	return NOTIFY_OK;
> +}
> +
> +static struct notifier_block cpuidle_hotplug_notifier = {
> +	.notifier_call = cpuidle_hotplug_notify,
> +};
> +
> +/**
>   * __cpuidle_driver_init - initialize the driver's internal data
>   * @drv: a valid pointer to a struct cpuidle_driver
>   *
> @@ -262,6 +305,9 @@ int cpuidle_register_driver(struct cpuidle_driver *drv)
>  	ret = __cpuidle_register_driver(drv);
>  	spin_unlock(&cpuidle_driver_lock);
>  
> +	if (!ret)
> +		ret = register_cpu_notifier(&cpuidle_hotplug_notifier);
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(cpuidle_register_driver);
> @@ -276,6 +322,8 @@ EXPORT_SYMBOL_GPL(cpuidle_register_driver);
>   */
>  void cpuidle_unregister_driver(struct cpuidle_driver *drv)
>  {
> +	unregister_cpu_notifier(&cpuidle_hotplug_notifier);
> +
>  	spin_lock(&cpuidle_driver_lock);
>  	__cpuidle_unregister_driver(drv);
>  	spin_unlock(&cpuidle_driver_lock);
> 


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