Re: [PATCH 1/2] do-not-allow-prio-less-than-one-in-cyclictest.patch

[John Kacur <jkacur@redhat.com>]

On Tue, Mar 9, 2010 at 7:02 PM, David Sommerseth <davids@redhat.com> wrote:
> On 07/03/10 23:37, John Kacur wrote:
>> On Sun, Mar 7, 2010 at 9:39 PM, Carsten Emde <C.Emde@osadl.org> wrote:
>>> If not in SMP testing mode, the priority may go below 1, if the specified
>>> priority is lower than the number of threads, e.g.
>>> # cyclictest -p2 -t3
>>> T: 0 (21970) P: 2 [..]
>>> T: 1 (21971) P: 1 [..]
>>> T: 2 (21972) P: 0 [..]
>>>
>>> Do not allow priority to go below 1.
>>>
>>> Signed-off-by: Carsten Emde <C.Emde@osadl.org>
>>>
>>> Index: rt-tests/src/cyclictest/cyclictest.c
>>> ===================================================================
>>> --- rt-tests.orig/src/cyclictest/cyclictest.c
>>> +++ rt-tests/src/cyclictest/cyclictest.c
>>> @@ -1304,7 +1304,7 @@ int main(int argc, char **argv)
>>>                }
>>>
>>>                par->prio = priority;
>>> -               if (!sameprio)
>>> +               if (priority > 1 && !sameprio)
>>>                        priority--;
>>>                 if      (priority && policy <= 1) par->policy = SCHED_FIFO;
>>>                 else if (priority && policy == 2) par->policy = SCHED_RR;
>>>
>>> --
>>
>> I'm not sure about this, why not allow a priority below 1? The code
>> below properly sets the third thead to SCHED_OTHER.
>> I could imagine wanting to test that too. If you don't want to go
>> below 1 then just set a higher prio, p3 in the scenario you
>> showed.
>
> Maybe I'm misreading and misunderstanding the patch ... but I believe
> the if statement should say:
>
>        if (priority > 0 && !sameprio)
>                priority--;
>
> Just to avoid the situation the commit log says, priority to go below 0.
>
>
> kind regards,
>
> David Sommerseth

The code in general there was buggy, so I reverted the patch that
caused the problems in the first place.
(assuming Clark merges it).

Now the code will read (as it did before)

 if (priority && !histogram && !smp && !numa)
                        priority--;
--
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