| Message ID | 20200917105900.4337-1-linmiaohe@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] mm: memcontrol: remove obsolete comment of mem_cgroup_unmark_under_oom() | expand |
On Thu 17-09-20 06:59:00, Miaohe Lin wrote: > Since commit 79dfdaccd1d5 ("memcg: make oom_lock 0 and 1 based rather than > counter"), the mem_cgroup_unmark_under_oom() is added and the comment of > the mem_cgroup_oom_unlock() is moved here. But this comment make no sense > here because mem_cgroup_oom_lock() does not operate on under_oom field. OK, so I've looked into this more deeply and I finally remember why we have this comment here. The point is that under_oom shouldn't underflow and that we have to explicitly check for > 0 because a new child memcg could have been added between mem_cgroup_mark_under_oom and mem_cgroup_unmark_under_oom. So the comment makes sense although it is not as helpful as it could be. I think that changing it to the following will be more usefule /* * Be careful about under_oom underflows becase a child memcg * could have neem added after mem_cgroup_mark_under_oom */ > > Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> > --- > mm/memcontrol.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index cd5f83de9a6f..e44f5afaf78b 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1848,10 +1848,6 @@ static void mem_cgroup_unmark_under_oom(struct mem_cgroup *memcg) > { > struct mem_cgroup *iter; > > - /* > - * When a new child is created while the hierarchy is under oom, > - * mem_cgroup_oom_lock() may not be called. Watch for underflow. > - */ > spin_lock(&memcg_oom_lock); > for_each_mem_cgroup_tree(iter, memcg) > if (iter->under_oom > 0) > -- > 2.19.1
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index cd5f83de9a6f..e44f5afaf78b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1848,10 +1848,6 @@ static void mem_cgroup_unmark_under_oom(struct mem_cgroup *memcg) { struct mem_cgroup *iter; - /* - * When a new child is created while the hierarchy is under oom, - * mem_cgroup_oom_lock() may not be called. Watch for underflow. - */ spin_lock(&memcg_oom_lock); for_each_mem_cgroup_tree(iter, memcg) if (iter->under_oom > 0)
Since commit 79dfdaccd1d5 ("memcg: make oom_lock 0 and 1 based rather than counter"), the mem_cgroup_unmark_under_oom() is added and the comment of the mem_cgroup_oom_unlock() is moved here. But this comment make no sense here because mem_cgroup_oom_lock() does not operate on under_oom field. Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> --- mm/memcontrol.c | 4 ---- 1 file changed, 4 deletions(-)