Re: [linux-pm] acpi_idle and max_cpus

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

On 06/18/2012 02:25 PM, Deepthi Dharwar wrote:
> Hi Daniel,
> 
> On 06/18/2012 01:48 AM, Daniel Lezcano wrote:
> 
>> On 06/15/2012 05:28 PM, Daniel Lezcano wrote:
>>>
>>> Hi all,
>>>
>>> I have a dual core Intel T9500.
>>>
>>> I boot the cpu with the acpi_idle driver and intel_idle enabled in the
>>> config.
>>>
>>> The kernel is booted with maxcpus=1.
>>>
>>> After the system has boot, I put cpu1 online via sysfs.
>>>
>>> But I don't see any 'cpuidle' directory in the cpu's sysfs entry:
>>>
>>> /sys/devices/system/cpu/cpu1/cpuidle (?)
>>>
>>> When I look at the code I see the notifier is present for hotplug in
>>> processor_driver.c and the cpuidle intel init routine should be called
>>> there.
>>>
> 
> 
> Yes, we have a hotplug notifier.
> Commit 99b72508  by Thomas Renninger fixed this issue.
> 
> Please let me know which kernel version you are running and what is idle
> driver registered ?

The kernel version is 3.5.0-rc1
The registered driver is acpi_idle (with intel_idle if I am not wrong).

Thomas's patch is in this version.

Maybe I am wrong but I think the patch is not correct because:

static int __cpuinit acpi_processor_add(struct acpi_device *device)
{

 ...

#ifdef CONFIG_SMP
	if (pr->id >= setup_max_cpus && pr->id != 0)
		return 0;
#endif

 ...

	per_cpu(processors, pr->id) = pr;

...
}

With max_cpus=1 we exit before setting up 'pr'.

So the condition in:

static int acpi_cpu_soft_notify(...)
{

	unsigned int cpu = (unsigned long)hcpu;
	struct acpi_processor *pr = per_cpu(processors, cpu);

	if (action == CPU_ONLINE && pr) {

...
}

Is always false because pr == NULL

I did the change but I don't still see the 'cpuidle' directory
appearing, I suspect also pr->flags.need_hotplug_init is not correctly
initialized but I did not investigate more.

>>> I am wondering is it a bug or an expected behavior ?
>>
>> Any thoughts on that ?
>>
>> Thanks
>>   -- Daniel
>>
>>
> 
> 
> Cheers
> Deepthi
> 


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