Re: [PATCH] sched: correct how RT task is picked

[Hillf Danton]

On Wed, May 11, 2011 at 4:43 PM, Yong Zhang <yong.zhang0@xxxxxxxxx> wrote:
> On Tue, May 10, 2011 at 9:04 PM, Hillf Danton <dhillf@xxxxxxxxx> wrote:
>> When picking RT task for given CPU,
>> [1] if the cpu is invalid for cpumask test, right result could not be
>
> 'cpu is invalid' means weather we care it or not, it's not real 'invalid'
>
If cpu is not cared, how to determine whether it is allowed for task to run?

>> reached even by further checking nr_cpus_allowed,
>> on the other hand, the input cpu is valid in two cases that
>> pick_next_highest_task_rt() is called, thus the invalid input cpu
>> looks over-concern.
>> [2] if the cpu is valid for cpumask test, further checking
>> nr_cpus_allowed looks overwork, since it is computed based on
>> cpus_allowed,
>
> No, cpumask_test_cpu(cpu, &p->cpus_allowed) doesn't mean
> p->rt.nr_cpus_allowed > 1.
>
If cpu is allowed for task to run, then why more cpus are enforced?

thanks
          Hillf
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