Re: [Xen-devel] [PATCH v7 for Xen 4.7 1/4] xen: enable per-VCPU parameter settings for RTDS scheduler

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.03.16 at 21:42, <lichong659@xxxxxxxxx> wrote:
> On Thu, Mar 17, 2016 at 5:03 AM, Dario Faggioli
> <dario.faggioli@xxxxxxxxxx> wrote:
>> On Wed, 2016-03-16 at 11:47 -0500, Chong Li wrote:
> 
>>
>>> --- a/xen/common/sched_rt.c
>>> +++ b/xen/common/sched_rt.c
>>> @@ -1129,24 +1145,22 @@ rt_dom_cntl(
>>>      struct vcpu *v;
>>>      unsigned long flags;
>>>      int rc = 0;
>>> +    xen_domctl_schedparam_vcpu_t local_sched;
>>> +    s_time_t period, budget;
>>> +    uint32_t index = 0;
>>>
>>>      switch ( op->cmd )
>>>      {
>>>      case XEN_DOMCTL_SCHEDOP_getinfo:
>>> -        if ( d->max_vcpus > 0 )
>>> -        {
>>> -            spin_lock_irqsave(&prv->lock, flags);
>>> -            svc = rt_vcpu(d->vcpu[0]);
>>> -            op->u.rtds.period = svc->period / MICROSECS(1);
>>> -            op->u.rtds.budget = svc->budget / MICROSECS(1);
>>> -            spin_unlock_irqrestore(&prv->lock, flags);
>>> -        }
>>> -        else
>>> -        {
>>> -            /* If we don't have vcpus yet, let's just return the
>>> defaults. */
>>> -            op->u.rtds.period = RTDS_DEFAULT_PERIOD;
>>> -            op->u.rtds.budget = RTDS_DEFAULT_BUDGET;
>>> -        }
>>> +        /* Return the default parameters.
>>> +         * A previous bug fixed here:
>>> +         * The default PERIOD or BUDGET should be divided by
>>> MICROSECS(1),
>>> +         * before returned to upper caller.
>>> +         */
>> Comment style (missing opening '/*').
>>
>> Also, putting this kind of things in comments is not at all ideal. If
>> doing this in this patch, you should mention it in the changelog. Or
>> you do it in a separate patch (that you put before this one in the
>> series).
>>
>> I'd say that, in this specific case, is not a big deal which one of the
>> two approaches you take (mentioning or separate patch), but the having
>> a separate one is indeed almost always preferable (e.g., the fix can be
>> backported).
> 
> If I choose mentioning, do I move the comment to the changelog? Or do I keep
> it here and say it again in the changelog?

Just consider what would happen if everyone mentioned in
comments the bugs they fixed. I think the answer to you question
is obvious then...

Jan


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