Re: [PATCH v2 1/3] hrtimer: add hrtimer_init_cpu()

[Stephane Eranian <eranian@google.com>]

On Wed, Sep 12, 2012 at 4:38 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, 2012-09-12 at 16:33 +0200, Stephane Eranian wrote:
>
>>
>> If I do:
>>   for_each_possible_cpu(cpu) {
>>        cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
>>        hr = &cpuctx->hrtimer;
>>        hrtimer_init(hr)
>> }
>> I don't understand why I would have to refer to per-cpu data
>> (hrtimer_bases) from
>> a CPU that is not equal to "cpu" here. Unless you're telling me it's
>> read-only data.
>
> No its not read only, but it is unused until you do *hrtimer_start*(),
> which will test and fix.
>
>> But still if it's per-cpu why not initialize with the correct CPU from
>> the start?
>
> To keep the interface simpler I guess. There's no great harm in your
> proposal, but it is strictly speaking superfluous. I'm not sure the max
> one time avoidance of a base swizzle is worth the extra interface, I'll
> leave that up to Thomas.
>
> Also, what Eric said ;-)

I am fine with dropping this patch. I just found it odd there was a per-cpu
data reference embedded deep into the call. I wanted things to be more
explicit. I know it works without the proposed change.