Re: [PATCH -v2 4/7] RT overloaded runqueues accounting

[Paul Menage]

On 10/22/07, Paul Jackson <pj@xxxxxxx> wrote:
> Steven wrote:
> > +void cpuset_rt_set_overload(struct task_struct *tsk, int cpu)
> > +{
> > +     cpu_set(cpu, task_cs(tsk)->rt_overload);
> > +}
>
> Question for Steven:
>
>   What locks are held when cpuset_rt_set_overload() is called?
>
> Questions for Paul Menage:
>
>   Does 'tsk' need to be locked for the above task_cs() call?

Cgroups doesn't change the locking rules for accessing a cpuset from a
task - you have to have one of:

- task_lock(task)

- callback_mutex

- be in an RCU section from the point when you call task_cs to the
point when you stop using its result. (Additionally, in this case
there's no guarantee that the task stays in this cpuset for the
duration of the RCU section).

Paul
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/