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Currently, cgroup_task_exit() adds thread group leaders with live member threads to their css_set's dying_tasks list (so cgroup.procs iteration can still see the leader), and cgroup_task_release() later removes them with list_del_init(&task->cg_list). An upcoming patch will defer the dying_tasks list addition, moving it from cgroup_task_exit() (called from do_exit()) to a new function called from finish_task_switch(). However, release_task() (which calls cgroup_task_release()) can run either before or after finish_task_switch(), creating a race where cgroup_task_release() might try to remove the task from dying_tasks before or while it's being added. Move the list_del_init() from cgroup_task_release() to cgroup_task_free() to fix this race. cgroup_task_free() runs from __put_task_struct(), which is always after both paths, making the cleanup safe. Cc: Dan Schatzberg <dschatzberg@meta.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Tejun Heo <tj@kernel.org>