On Sat, Feb 20, 2010 at 6:22 AM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> 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 ?
Yes
> Do you have a test set for checking this behavior ?
Run ./cgroup_event_listener to listen any event in the cgroup. Remove directory
of the cgroup (cgroup_event_listener will detect it). And check 'num_cgroups'
column in /proc/cgroups.
>
> 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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