Commit f43caa2a authored by Michal Koutný's avatar Michal Koutný Committed by Tejun Heo
Browse files

cgroup: Clean up css_set task traversal 



css_task_iter stores pointer to head of each iterable list, this dates
back to commit 0f0a2b4f ("cgroup: reorganize css_task_iter") when we
did not store cur_cset. Let us utilize list heads directly in cur_cset
and streamline css_task_iter_advance_css_set a bit. This is no
intentional function change.

Signed-off-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 9c974c77

include/linux/cgroup.h

+0 −3
Original line number Diff line number Diff line
@@ -58,9 +58,6 @@ struct css_task_iter { 
	struct list_head		*tcset_head;



	struct list_head		*task_pos;

	struct list_head		*tasks_head;

	struct list_head		*mg_tasks_head;

	struct list_head		*dying_tasks_head;



	struct list_head		*cur_tasks_head;

	struct css_set			*cur_cset;

kernel/cgroup/cgroup.c

+28 −33
Original line number Diff line number Diff line
@@ -4391,29 +4391,24 @@ static void css_task_iter_advance_css_set(struct css_task_iter *it) 


	lockdep_assert_held(&css_set_lock);



	/* Advance to the next non-empty css_set */

	do {

		cset = css_task_iter_next_css_set(it);

		if (!cset) {

			it->task_pos = NULL;

			return;

		}

	} while (!css_set_populated(cset) && list_empty(&cset->dying_tasks));



	/* Advance to the next non-empty css_set and find first non-empty tasks list*/

	while ((cset = css_task_iter_next_css_set(it))) {

		if (!list_empty(&cset->tasks)) {

		it->task_pos = cset->tasks.next;

			it->cur_tasks_head = &cset->tasks;

			break;

		} else if (!list_empty(&cset->mg_tasks)) {

		it->task_pos = cset->mg_tasks.next;

			it->cur_tasks_head = &cset->mg_tasks;

	} else {

		it->task_pos = cset->dying_tasks.next;

			break;

		} else if (!list_empty(&cset->dying_tasks)) {

			it->cur_tasks_head = &cset->dying_tasks;

			break;

		}



	it->tasks_head = &cset->tasks;

	it->mg_tasks_head = &cset->mg_tasks;

	it->dying_tasks_head = &cset->dying_tasks;

	}

	if (!cset) {

		it->task_pos = NULL;

		return;

	}

	it->task_pos = it->cur_tasks_head->next;



	/*

	 * We don't keep css_sets locked across iteration steps and thus
@@ -4458,24 +4453,24 @@ static void css_task_iter_advance(struct css_task_iter *it) 
repeat:

	if (it->task_pos) {

		/*

		 * Advance iterator to find next entry.  cset->tasks is

		 * consumed first and then ->mg_tasks.  After ->mg_tasks,

		 * we move onto the next cset.

		 * Advance iterator to find next entry. We go through cset

		 * tasks, mg_tasks and dying_tasks, when consumed we move onto

		 * the next cset.

		 */

		if (it->flags & CSS_TASK_ITER_SKIPPED)

			it->flags &= ~CSS_TASK_ITER_SKIPPED;

		else

			it->task_pos = it->task_pos->next;



		if (it->task_pos == it->tasks_head) {

			it->task_pos = it->mg_tasks_head->next;

			it->cur_tasks_head = it->mg_tasks_head;

		if (it->task_pos == &it->cur_cset->tasks) {

			it->cur_tasks_head = &it->cur_cset->mg_tasks;

			it->task_pos = it->cur_tasks_head->next;

		}

		if (it->task_pos == it->mg_tasks_head) {

			it->task_pos = it->dying_tasks_head->next;

			it->cur_tasks_head = it->dying_tasks_head;

		if (it->task_pos == &it->cur_cset->mg_tasks) {

			it->cur_tasks_head = &it->cur_cset->dying_tasks;

			it->task_pos = it->cur_tasks_head->next;

		}

		if (it->task_pos == it->dying_tasks_head)

		if (it->task_pos == &it->cur_cset->dying_tasks)

			css_task_iter_advance_css_set(it);

	} else {

		/* called from start, proceed to the first cset */
@@ -4493,12 +4488,12 @@ repeat: 
			goto repeat;



		/* and dying leaders w/o live member threads */

		if (it->cur_tasks_head == it->dying_tasks_head &&

		if (it->cur_tasks_head == &it->cur_cset->dying_tasks &&

		    !atomic_read(&task->signal->live))

			goto repeat;

	} else {

		/* skip all dying ones */

		if (it->cur_tasks_head == it->dying_tasks_head)

		if (it->cur_tasks_head == &it->cur_cset->dying_tasks)

			goto repeat;

	}

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE