Re: [PATCH v10 4/4] cgroups: implement the PIDs subsystem

[Tejun Heo <tj@kernel.org>]

Hello, Aleksa.

On Sat, Apr 25, 2015 at 12:07:34AM +1000, Aleksa Sarai wrote:
> Would something like this suffice?
> 
> struct cgroup_subsys_state *task_get_css(struct task_struct *task, int
> subsys_id) {
>         bool have_ref = false;
>         struct cgroup_subsys_state *css;
> 
>         while(!have_ref) {
>                 rcu_read_lock();
>                 css = task_css(task, subsys_id);
>                 have_ref = !css_tryget(css);
>                 rcu_read_unlock();
>         }
> 
>         return css;
> }

I was thinking why this felt so familiar and realized that I have the
patch pending.

 http://lkml.kernel.org/g/1428350318-8215-8-git-send-email-tj@kernel.org

Please feel free to include it in the patch series.  I'll sort out the
merging later.

> Also, as a side note (in the same vein I guess), does a ref on a
> css_set give you an implicit ref on a css inside that css_set, or are
> those two orthogonal operations?

Yes, it does, but if you're gonna depend on that, please document that.

Thanks.

-- 
tejun