Re: [PATCH 4/7] cgroups: New cancel_attach_task subsystem callback

Paul Menage
2011-07-26T00:58:16Z

On Mon, Jul 11, 2011 at 7:15 AM, Frederic Weisbecker <fweisbec@gmail.com> wrote:
> To cancel a process attachment on a subsystem, we only call the
> cancel_attach() callback once on the leader but we have no
> way to cancel the attachment individually for each member of
> the process group.
>
> This is going to be needed for the max number of tasks susbystem
> that is coming.
>
> To prepare for this integration, call a new cancel_attach_task()
> callback on each task of the group until we reach the member that
> failed to attach.
>
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

Acked-by: Paul Menage <menage@google.com>

> Cc: Paul Menage <menage@google.com>
> Cc: Li Zefan <lizf@cn.fujitsu.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Aditya Kali <adityakali@google.com>
> ---
>  include/linux/cgroup.h |    1 +
>  kernel/cgroup.c        |   15 ++++++++++++---
>  2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index e8288a0..94454143 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -472,6 +472,7 @@ struct cgroup_subsys {
>                               struct task_struct *tsk);
>        void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
>                              struct task_struct *tsk);
> +       void (*cancel_attach_task)(struct cgroup *cgrp, struct task_struct *tsk);
>        void (*pre_attach)(struct cgroup *cgrp);
>        void (*attach_task)(struct cgroup *cgrp, struct cgroup *old_cgrp, struct task_struct *tsk);
>        void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index c3ee4cf..210dc05 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -1989,7 +1989,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
>  {
>        int retval, i, group_size;
>        struct cgroup_subsys *ss, *failed_ss = NULL;
> -       bool cancel_failed_ss = false;
> +       struct task_struct *failed_task = NULL;
>        /* guaranteed to be initialized later, but the compiler needs this */
>        struct cgroup *oldcgrp = NULL;
>        struct css_set *oldcg;
> @@ -2077,7 +2077,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
>                                retval = ss->can_attach_task(cgrp, oldcgrp, tsk);
>                                if (retval) {
>                                        failed_ss = ss;
> -                                       cancel_failed_ss = true;
> +                                       failed_task = tsk;
>                                        goto out_cancel_attach;
>                                }
>                        }
> @@ -2172,8 +2172,17 @@ out_cancel_attach:
>        /* same deal as in cgroup_attach_task */
>        if (retval) {
>                for_each_subsys(root, ss) {
> +                       if (ss->cancel_attach_task && (ss != failed_ss || failed_task)) {
> +                               for (i = 0; i < group_size; i++) {
> +                                       tsk = flex_array_get_ptr(group, i);
> +                                       if (tsk == failed_task)
> +                                               break;
> +                                       ss->cancel_attach_task(cgrp, tsk);
> +                               }
> +                       }
> +
>                        if (ss == failed_ss) {
> -                               if (cancel_failed_ss && ss->cancel_attach)
> +                               if (failed_task && ss->cancel_attach)
>                                        ss->cancel_attach(ss, cgrp, leader);
>                                break;
>                        }
> --
> 1.7.5.4
>
>