On Sat, 20 Feb 2010 00:28:17 +0200
"Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> wrote:
> Events should be removed after rmdir of cgroup directory, but before
> destroying subsystem state objects. Let's take reference to cgroup
> directory dentry to do that.
>
> Signed-off-by: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Okay, I welcome this.
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hioryu@xxxxxxxxxxxxxx>
Just a quesion...After this change, if cgroup has remaining event,
cgroup is removed by workqueue of event->remove() -> d_put(), finally. Right ?
Do you have a test set for checking this behavior ?
Thanks,
-Kame
> ---
> include/linux/cgroup.h | 3 ---
> kernel/cgroup.c | 8 ++++++++
> mm/memcontrol.c | 9 ---------
> 3 files changed, 8 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index 64cebfe..1719c75 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -395,9 +395,6 @@ struct cftype {
> * closes the eventfd or on cgroup removing.
> * This callback must be implemented, if you want provide
> * notification functionality.
> - *
> - * Be careful. It can be called after destroy(), so you have
> - * to keep all nesessary data, until all events are removed.
> */
> int (*unregister_event)(struct cgroup *cgrp, struct cftype *cft,
> struct eventfd_ctx *eventfd);
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 46903cb..d142524 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -2979,6 +2979,7 @@ static void cgroup_event_remove(struct work_struct *work)
>
> eventfd_ctx_put(event->eventfd);
> kfree(event);
> + dput(cgrp->dentry);
> }
>
> /*
> @@ -3099,6 +3100,13 @@ static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
> goto fail;
> }
>
> + /*
> + * Events should be removed after rmdir of cgroup directory, but before
> + * destroying subsystem state objects. Let's take reference to cgroup
> + * directory dentry to do that.
> + */
> + dget(cgrp->dentry);
> +
> spin_lock(&cgrp->event_list_lock);
> list_add(&event->list, &cgrp->event_list);
> spin_unlock(&cgrp->event_list_lock);
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a443c30..8fe6e7f 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3358,12 +3358,6 @@ static int mem_cgroup_register_event(struct cgroup *cgrp, struct cftype *cft,
> }
> }
>
> - /*
> - * We need to increment refcnt to be sure that all thresholds
> - * will be unregistered before calling __mem_cgroup_free()
> - */
> - mem_cgroup_get(memcg);
> -
> if (type == _MEM)
> rcu_assign_pointer(memcg->thresholds, thresholds_new);
> else
> @@ -3457,9 +3451,6 @@ assign:
> /* To be sure that nobody uses thresholds before freeing it */
> synchronize_rcu();
>
> - for (i = 0; i < thresholds->size - size; i++)
> - mem_cgroup_put(memcg);
> -
> kfree(thresholds);
> unlock:
> mutex_unlock(&memcg->thresholds_lock);
> --
> 1.6.6.2
>
>
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