On Fri, Jun 21, 2013 at 03:51:17PM -0700, 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. > > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> > Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx Applied 1-3 to cgroup/for-3.11. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
