On Tue, Oct 27, 2020 at 8:51 PM Muchun Song <songmuc...@bytedance.com> wrote: > > The rcu_read_lock/unlock only can guarantee that the memcg will > not be freed, but it cannot guarantee the success of css_get to > memcg. > > If the whole process of a cgroup offlining is completed between > reading a objcg->memcg pointer and bumping the css reference on > another CPU, and there are exactly 0 external references to this > memory cgroup (how we get to the obj_cgroup_charge() then?), > css_get() can change the ref counter from 0 back to 1. > > Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") > Signed-off-by: Muchun Song <songmuc...@bytedance.com> > Acked-by: Roman Gushchin <g...@fb.com>
Reviewed-by: Shakeel Butt <shake...@google.com>