On Tue 14-05-24 13:11:06, Xiu Jianfeng wrote:
> The event_list for memcg is only valid for v1 and not used for v2,
> so it's unnessesary to handle event_list for v2.
You are right but the code as is works just fine. The list will be
empty. It is true that we do not need to take event_list_lock lock but
nobody should be using this lock anyway. Also the offline callback is
not particularly hot path. So why do we want to change the code?
>
> Signed-off-by: Xiu Jianfeng <xiujianfeng@xxxxxxxxxx>
> ---
> mm/memcontrol.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index d127c9c5fabf..4254f9cd05f4 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5881,12 +5881,14 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
> * Notify userspace about cgroup removing only after rmdir of cgroup
> * directory to avoid race between userspace and kernelspace.
> */
> - spin_lock_irq(&memcg->event_list_lock);
> - list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
> - list_del_init(&event->list);
> - schedule_work(&event->remove);
> + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
> + spin_lock_irq(&memcg->event_list_lock);
> + list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
> + list_del_init(&event->list);
> + schedule_work(&event->remove);
> + }
> + spin_unlock_irq(&memcg->event_list_lock);
> }
> - spin_unlock_irq(&memcg->event_list_lock);
>
> page_counter_set_min(&memcg->memory, 0);
> page_counter_set_low(&memcg->memory, 0);
> --
> 2.34.1
--
Michal Hocko
SUSE Labs
