Re: [PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup

[Paul Menage <menage@google.com>]

On Tue, Nov 23, 2010 at 9:37 PM, Colin Cross <ccross@android.com> wrote:
> @@ -364,12 +372,8 @@ static void __put_css_set(struct css_set *cg, int taskexit)
>                struct cgroup *cgrp = link->cgrp;
>                list_del(&link->cg_link_list);
>                list_del(&link->cgrp_link_list);
> -               if (atomic_dec_and_test(&cgrp->count) &&
> -                   notify_on_release(cgrp)) {
> -                       if (taskexit)
> -                               set_bit(CGRP_RELEASABLE, &cgrp->flags);
> +               if (atomic_dec_and_test(&cgrp->count))
>                        check_for_release(cgrp);
> -               }

We seem to have lost some notify_on_release() checks - maybe move that
to check_for_release()?
>  /* Caller must verify that the css is not for root cgroup */
> +void __css_get(struct cgroup_subsys_state *css, int count)
> +{
> +       atomic_add(count, &css->refcnt);
> +       set_bit(CGRP_RELEASABLE, &css->cgroup->flags);
> +}

Is css_get() the right place to be putting this? It's not clear to me
why a subsystem taking a refcount on a cgroup's state should render it
releasable when it drops that refcount.

Should we maybe clear the CGRP_RELEASABLE flag right before doing the
userspace callback?

Paul