Re: [PATCH 1/2] perf_events: add cgroup support (v8)

[Peter Zijlstra <peterz@infradead.org>]

On Thu, 2011-01-20 at 15:30 +0200, Stephane Eranian wrote:
> @@ -4259,8 +4261,20 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
>  
>         /* Reassign the task to the init_css_set. */
>         task_lock(tsk);
> +       /*
> +        * we mask interrupts to prevent:
> +        * - timer tick to cause event rotation which
> +        *   could schedule back in cgroup events after
> +        *   they were switched out by perf_cgroup_sched_out()
> +        *
> +        * - preemption which could schedule back in cgroup events
> +        */
> +       local_irq_save(flags);
> +       perf_cgroup_sched_out(tsk);
>         cg = tsk->cgroups;
>         tsk->cgroups = &init_css_set;
> +       perf_cgroup_sched_in(tsk);
> +       local_irq_restore(flags);
>         task_unlock(tsk);
>         if (cg)
>                 put_css_set_taskexit(cg); 

So you too need a callback on cgroup change there.. Li, Paul, any chance
we can fix this cgroup_subsys::exit callback? The scheduler code needs
to do funny thing because its in the wrong place as well.