Messages in this thread Patch in this message | | | Date | Wed, 11 May 2011 16:43:49 +0800 | Subject | Re: [PATCH] sched: correct how RT task is picked | From | Yong Zhang <> |
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On Tue, May 10, 2011 at 9:04 PM, Hillf Danton <dhillf@gmail.com> 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'
> 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.
Thanks, Yong
> what is more, the combination of cpus_allowed and nr_cpus_allowed > could lead to incorrect result if the input cpu == rq->cpu, as in the > case of next_prio() where no pulling task is concerned. > > In this work, invalid cpu is not removed but leads to negative result, > but nr_cpus_allowed is. > > Signed-off-by: Hillf Danton <dhillf@gmail.com> > --- > > --- a/kernel/sched_rt.c 2011-04-27 11:48:50.000000000 +0800 > +++ b/kernel/sched_rt.c 2011-05-10 20:30:38.000000000 +0800 > @@ -1149,10 +1149,12 @@ static void deactivate_task(struct rq *r > > static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu) > { > - if (!task_running(rq, p) && > - (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) && > - (p->rt.nr_cpus_allowed > 1)) > - return 1; > + if (!task_running(rq, p)) { > + if (cpu < 0) > + return 0; > + if (cpumask_test_cpu(cpu, &p->cpus_allowed)) > + return 1; > + } > return 0; > } >
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