Re: [PATCH V2] ACPI/Processor: Rework processor throttling with work_on_cpu()

[Lan Tianyu <tianyu.lan@intel.com>]

On 02/26/2014 09:30 PM, Rafael J. Wysocki wrote:
> On Wednesday, February 26, 2014 09:03:05 PM Lan Tianyu wrote:
>> acpi_processor_set_throttling() uses set_cpus_allowed_ptr() to make
>> sure struct acpi_processor->acpi_processor_set_throttling() callback
>> run on associated cpu. But the function maybe called in a worker which
>> has been bound to a cpu. The patch is to replace set_cpus_allowed_ptr()
>> with work_on_cpu().
>>
>> Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
>
> OK
>
> I suppose we need this in -stable?

Yes.

>
> Which series of -stable should it go to?  All of them or just recent?

I think it should be all of them. Checking thermal zone device in a 
worker was already there before 2.6.30-rc1 when moved thermal trip 
handling to generic thermal layer from ACPI.

commit b1569e99c795bf83b4ddf41c4f1c42761ab7f75e
Author: Matthew Garrett <mjg59@srcf.ucam.org>
Date:   Wed Dec 3 17:55:32 2008 +0000

     ACPI: move thermal trip handling to generic thermal layer

     The ACPI code currently carries its own thermal trip handling, 
meaning that any other thermal implementation will need to reimplement
it. Move the code to the generic thermal layer.

>
>
>> ---
>> Change since v1:
>>         Remove temp variable p_throttling and reference struct
>> acpi_processor_throttling pointer directly from struct
>> acpi_processor.
>>
>>   drivers/acpi/processor_throttling.c | 69 +++++++++++++++++--------------------
>>   1 file changed, 32 insertions(+), 37 deletions(-)
>>
>> diff --git a/drivers/acpi/processor_throttling.c b/drivers/acpi/processor_throttling.c
>> index 28baa05..84243c3 100644
>> --- a/drivers/acpi/processor_throttling.c
>> +++ b/drivers/acpi/processor_throttling.c
>> @@ -56,6 +56,12 @@ struct throttling_tstate {
>>   	int target_state;		/* target T-state */
>>   };
>>
>> +struct acpi_processor_throttling_arg {
>> +	struct acpi_processor *pr;
>> +	int target_state;
>> +	bool force;
>> +};
>> +
>>   #define THROTTLING_PRECHANGE       (1)
>>   #define THROTTLING_POSTCHANGE      (2)
>>
>> @@ -1060,16 +1066,24 @@ static int acpi_processor_set_throttling_ptc(struct acpi_processor *pr,
>>   	return 0;
>>   }
>>
>> +static long acpi_processor_throttling_fn(void *data)
>> +{
>> +	struct acpi_processor_throttling_arg *arg = data;
>> +	struct acpi_processor *pr = arg->pr;
>> +
>> +	return pr->throttling.acpi_processor_set_throttling(pr,
>> +			arg->target_state, arg->force);
>> +}
>> +
>>   int acpi_processor_set_throttling(struct acpi_processor *pr,
>>   						int state, bool force)
>>   {
>> -	cpumask_var_t saved_mask;
>>   	int ret = 0;
>>   	unsigned int i;
>>   	struct acpi_processor *match_pr;
>>   	struct acpi_processor_throttling *p_throttling;
>> +	struct acpi_processor_throttling_arg arg;
>>   	struct throttling_tstate t_state;
>> -	cpumask_var_t online_throttling_cpus;
>>
>>   	if (!pr)
>>   		return -EINVAL;
>> @@ -1080,14 +1094,6 @@ int acpi_processor_set_throttling(struct acpi_processor *pr,
>>   	if ((state < 0) || (state > (pr->throttling.state_count - 1)))
>>   		return -EINVAL;
>>
>> -	if (!alloc_cpumask_var(&saved_mask, GFP_KERNEL))
>> -		return -ENOMEM;
>> -
>> -	if (!alloc_cpumask_var(&online_throttling_cpus, GFP_KERNEL)) {
>> -		free_cpumask_var(saved_mask);
>> -		return -ENOMEM;
>> -	}
>> -
>>   	if (cpu_is_offline(pr->id)) {
>>   		/*
>>   		 * the cpu pointed by pr->id is offline. Unnecessary to change
>> @@ -1096,17 +1102,15 @@ int acpi_processor_set_throttling(struct acpi_processor *pr,
>>   		return -ENODEV;
>>   	}
>>
>> -	cpumask_copy(saved_mask, &current->cpus_allowed);
>>   	t_state.target_state = state;
>>   	p_throttling = &(pr->throttling);
>> -	cpumask_and(online_throttling_cpus, cpu_online_mask,
>> -		    p_throttling->shared_cpu_map);
>> +
>>   	/*
>>   	 * The throttling notifier will be called for every
>>   	 * affected cpu in order to get one proper T-state.
>>   	 * The notifier event is THROTTLING_PRECHANGE.
>>   	 */
>> -	for_each_cpu(i, online_throttling_cpus) {
>> +	for_each_cpu_and(i, cpu_online_mask, p_throttling->shared_cpu_map) {
>>   		t_state.cpu = i;
>>   		acpi_processor_throttling_notifier(THROTTLING_PRECHANGE,
>>   							&t_state);
>> @@ -1118,21 +1122,18 @@ int acpi_processor_set_throttling(struct acpi_processor *pr,
>>   	 * it can be called only for the cpu pointed by pr.
>>   	 */
>>   	if (p_throttling->shared_type == DOMAIN_COORD_TYPE_SW_ANY) {
>> -		/* FIXME: use work_on_cpu() */
>> -		if (set_cpus_allowed_ptr(current, cpumask_of(pr->id))) {
>> -			/* Can't migrate to the pr->id CPU. Exit */
>> -			ret = -ENODEV;
>> -			goto exit;
>> -		}
>> -		ret = p_throttling->acpi_processor_set_throttling(pr,
>> -						t_state.target_state, force);
>> +		arg.pr = pr;
>> +		arg.target_state = state;
>> +		arg.force = force;
>> +		ret = work_on_cpu(pr->id, acpi_processor_throttling_fn, &arg);
>>   	} else {
>>   		/*
>>   		 * When the T-state coordination is SW_ALL or HW_ALL,
>>   		 * it is necessary to set T-state for every affected
>>   		 * cpus.
>>   		 */
>> -		for_each_cpu(i, online_throttling_cpus) {
>> +		for_each_cpu_and(i, cpu_online_mask,
>> +		    p_throttling->shared_cpu_map) {
>>   			match_pr = per_cpu(processors, i);
>>   			/*
>>   			 * If the pointer is invalid, we will report the
>> @@ -1153,13 +1154,12 @@ int acpi_processor_set_throttling(struct acpi_processor *pr,
>>   					"on CPU %d\n", i));
>>   				continue;
>>   			}
>> -			t_state.cpu = i;
>> -			/* FIXME: use work_on_cpu() */
>> -			if (set_cpus_allowed_ptr(current, cpumask_of(i)))
>> -				continue;
>> -			ret = match_pr->throttling.
>> -				acpi_processor_set_throttling(
>> -				match_pr, t_state.target_state, force);
>> +
>> +			arg.pr = match_pr;
>> +			arg.target_state = state;
>> +			arg.force = force;
>> +			ret = work_on_cpu(pr->id, acpi_processor_throttling_fn,
>> +				&arg);
>>   		}
>>   	}
>>   	/*
>> @@ -1168,17 +1168,12 @@ int acpi_processor_set_throttling(struct acpi_processor *pr,
>>   	 * affected cpu to update the T-states.
>>   	 * The notifier event is THROTTLING_POSTCHANGE
>>   	 */
>> -	for_each_cpu(i, online_throttling_cpus) {
>> +	for_each_cpu_and(i, cpu_online_mask, p_throttling->shared_cpu_map) {
>>   		t_state.cpu = i;
>>   		acpi_processor_throttling_notifier(THROTTLING_POSTCHANGE,
>>   							&t_state);
>>   	}
>> -	/* restore the previous state */
>> -	/* FIXME: use work_on_cpu() */
>> -	set_cpus_allowed_ptr(current, saved_mask);
>> -exit:
>> -	free_cpumask_var(online_throttling_cpus);
>> -	free_cpumask_var(saved_mask);
>> +
>>   	return ret;
>>   }
>>
>>
>


-- 
Best Regards
Tianyu Lan