Hi, Viresh
On 05/20/2013 03:12 PM, Viresh Kumar wrote:
> Hi Michael,
>
> I haven't followed this mail chain earlier and saw this mail only as I am
> added in cc now. I probably have answers to few questions here:
Thanks for your quick respond :)
>
> On 20 May 2013 12:36, Michael Wang <wangyun@xxxxxxxxxxxxxxxxxx> wrote:
>> On 05/20/2013 02:58 PM, Michael Wang wrote:
>>> On 05/20/2013 02:47 PM, Borislav Petkov wrote:
>>>> On Mon, May 20, 2013 at 02:23:37PM +0800, Michael Wang wrote:
>>>>> On 05/20/2013 12:50 PM, Borislav Petkov wrote:
>>>>> So there are two questions here:
>>>>> 1. Is gov_queue_work() want to queue the work on offline cpu?
>
> No. We are only working with online cpus now in cpufreq core and governors.
>
>>> Besides, the cpu gov_queue_work() is using 'policy->cpus' which seems to
>>> be updated during UP DOWN notify, I think they are supposed to be online.
>>>
>>> But we need expert in cpufreq to confirm all these...
>
> I confirm this. policy->cpus only contains online cpus.. and
> policy->related_cpus
> always contain online+offline cpus.
Nice to be confirmed :)
>
>> And I guess this may help to reduce the chance to trigger WARN:
>>
>> diff --git a/drivers/cpufreq/cpufreq_governor.c
>> b/drivers/cpufreq/cpufreq_governor.c
>> index 443442d..0f96013 100644
>> --- a/drivers/cpufreq/cpufreq_governor.c
>> +++ b/drivers/cpufreq/cpufreq_governor.c
>> @@ -180,7 +180,7 @@ void gov_queue_work(struct dbs_data *dbs_data,
>> struct cpufreq_policy *policy,
>> if (!all_cpus) {
>> __gov_queue_work(smp_processor_id(), dbs_data, delay);
>> } else {
>> - for_each_cpu(i, policy->cpus)
>> + for_each_cpu_and(i, policy->cpus, cpu_online_mask)
>> __gov_queue_work(i, dbs_data, delay);
>> }
>> }
>
> Not required at all... policy->cpus is guaranteed to have only online cpus.
Yeah, that's right, I guess the issue is, although the policy->cpus is
correct at a given time, after get cpu from it, it's possible to be
changed, unless we disabled preempt or irq, or hotplug before we use it...
Like such issue cases:
get x from policy->cpus
DOWN notifier
change policy->cpus
do offline x
send ipi to x
Will that happen?
Regards,
Michael Wang
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