On 2013/6/26 2:48, Tejun Heo wrote: > task->cgroups is a RCU pointer pointing to struct css_set. A task > switches to a different css_set on cgroup migration but a css_set > doesn't change once created and its pointers to cgroup_subsys_states > aren't RCU protected. > > task_subsys_state[_check]() is the macro to acquire css given a task > and subsys_id pair. It RCU-dereferences task->cgroups->subsys[] not > task->cgroups, so the RCU pointer task->cgroups ends up being > dereferenced without read_barrier_depends() after it. It's broken. > > Fix it by introducing task_css_set[_check]() which does > RCU-dereference on task->cgroups. task_subsys_state[_check]() is > reimplemented to directly dereference ->subsys[] of the css_set > returned from task_css_set[_check](). > > This removes some of sparse RCU warnings in cgroup. > > v2: Fixed unbalanced parenthsis and there's no need to use > rcu_dereference_raw() when !CONFIG_PROVE_RCU. Both spotted by Li. > > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> > Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx Acked-by: Li Zefan <lizefan@xxxxxxxxxx> _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
