> On Jul 24, 2024, at 02:39, Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote: > > On Mon, Jul 22, 2024 at 03:08:10PM GMT, Muchun Song wrote: >> The obj_cgroup_memcg() is supposed to safe to prevent the returned >> memory cgroup from being freed only when the caller is holding the >> rcu read lock or objcg_lock or cgroup_mutex. It is very easy to >> ignore thoes conditions when users call some upper APIs which call >> obj_cgroup_memcg() internally like mem_cgroup_from_slab_obj() (See >> the link below). So it is better to add lockdep assertion to >> obj_cgroup_memcg() to find those issues ASAP. >> >> Because there is no user of obj_cgroup_memcg() holding objcg_lock >> to make the returned memory cgroup safe, do not add objcg_lock >> assertion (We should export objcg_lock if we really want to do) >> and leave a comment to indicate it is intentional. >> > > Do we expect non-memcg code to access objcg_lock? To me this is some > internal implementation detail of memcg and should not be accessible > outside memcg code. So, I would recommend to not mention objcg_lock at > all. Also make sense. Will update next version.
