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SubjectRe: [PATCH] cgroup: Fix potential race between cgroup_exit and migrate path
On Wed, Aug 30, 2017 at 05:55:45PM -0700, Tejun Heo wrote:
> Would something like the following fix the issue? Thanks.
>
> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index df2e0f1..cd85ca0 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -683,7 +683,7 @@ static void css_set_move_task(struct task_struct *task,
> if (it->task_pos == &task->cg_list)
> css_task_iter_advance(it);
>
> - list_del_init(&task->cg_list);
> + list_del(&task->cg_list);
> if (!css_set_populated(from_cset))
> css_set_update_populated(from_cset, false);
> } else {

Oops, more like the following.

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index df2e0f1..6f34025 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -683,7 +683,7 @@ static void css_set_move_task(struct task_struct *task,
if (it->task_pos == &task->cg_list)
css_task_iter_advance(it);

- list_del_init(&task->cg_list);
+ list_del(&task->cg_list);
if (!css_set_populated(from_cset))
css_set_update_populated(from_cset, false);
} else {
@@ -702,6 +702,8 @@ static void css_set_move_task(struct task_struct *task,
rcu_assign_pointer(task->cgroups, to_cset);
list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
&to_cset->tasks);
+ } else {
+ INIT_LIST_HEAD(&task->cg_list);
}
}


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