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

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

On 08/06/2013 04:10 PM, Rafael J. Wysocki wrote:
> On Tuesday, August 06, 2013 10:36:21 AM Daniel Lezcano wrote:
>> 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 ?
> 
> Honestly, I didn't have the time to look into that and Len is on vacation.
> 
> It's on my todo list, however.

Ah, ok. 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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