Commit 6fe96014 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Tejun Heo
Browse files

cgroup: avoid the unnecessary list_add(dying_tasks) in cgroup_exit() 



cgroup_exit() needs to do this only if the exiting task is a leader and it
is not the last live thread.  The patch doesn't use delay_group_leader(),
atomic_read(signal->live) matches the code css_task_iter_advance() more.

cgroup_release() can now check list_empty(task->cg_list) before it takes
css_set_lock and calls ss_set_skip_task_iters().

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 1805c172

kernel/cgroup/cgroup.c

+9 −5
Original line number Diff line number Diff line
@@ -6701,8 +6701,10 @@ void cgroup_exit(struct task_struct *tsk) 
	WARN_ON_ONCE(list_empty(&tsk->cg_list));

	cset = task_css_set(tsk);

	css_set_move_task(tsk, cset, NULL, false);

	list_add_tail(&tsk->cg_list, &cset->dying_tasks);

	cset->nr_tasks--;

	/* matches the signal->live check in css_task_iter_advance() */

	if (thread_group_leader(tsk) && atomic_read(&tsk->signal->live))

		list_add_tail(&tsk->cg_list, &cset->dying_tasks);



	if (dl_task(tsk))

		dec_dl_tasks_cs(tsk);
@@ -6729,11 +6731,13 @@ void cgroup_release(struct task_struct *task) 
		ss->release(task);

	} while_each_subsys_mask();



	if (!list_empty(&task->cg_list)) {

		spin_lock_irq(&css_set_lock);

		css_set_skip_task_iters(task_css_set(task), task);

		list_del_init(&task->cg_list);

		spin_unlock_irq(&css_set_lock);

	}

}



void cgroup_free(struct task_struct *task)

{