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

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

On 2014年02月26日 09:23, Rafael J. Wysocki wrote:
> On Friday, February 21, 2014 01:35:45 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>
>> ---
>>  drivers/acpi/processor_throttling.c | 70 +++++++++++++++++--------------------
>>  1 file changed, 33 insertions(+), 37 deletions(-)
>>
>> diff --git a/drivers/acpi/processor_throttling.c b/drivers/acpi/processor_throttling.c
>> index 28baa05..2db105a 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 +1066,25 @@ 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;
>> +	struct acpi_processor_throttling *p_throttling = &pr->throttling;
>> +
>> +	return p_throttling->acpi_processor_set_throttling(pr,
>> +			arg->target_state, arg->force);
> 
> What about doing
> 
> 	return pr->throttling.acpi_processor_set_throttling(...);
> 
> directly without using the extra p_throttling pointer?

This is better. I will update soon.

> 
>> +}
>> +
>>  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 +1095,6 @@ 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 +1103,15 @@ 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 +1123,18 @@ 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 +1155,12 @@ 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 +1169,12 @@ 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