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Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c15
1 files changed, 12 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index c6bd67b3fcf6..548d8d4e86d0 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4595,10 +4595,19 @@ void cgroup_post_fork(struct task_struct *child)
{
if (use_task_css_set_links) {
write_lock(&css_set_lock);
- task_lock(child);
- if (list_empty(&child->cg_list))
+ if (list_empty(&child->cg_list)) {
+ /*
+ * It's safe to use child->cgroups without task_lock()
+ * here because we are protected through
+ * threadgroup_change_begin() against concurrent
+ * css_set change in cgroup_task_migrate(). Also
+ * the task can't exit at that point until
+ * wake_up_new_task() is called, so we are protected
+ * against cgroup_exit() setting child->cgroup to
+ * init_css_set.
+ */
list_add(&child->cg_list, &child->cgroups->tasks);
- task_unlock(child);
+ }
write_unlock(&css_set_lock);
}
}