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Commit ecb9d535 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: reorganize css_task_iter functions 



* Rename css_advance_task_iter() to css_task_iter_advance_css_set()
  and make it clear it->task_pos too at the end of the iteration.

* Factor out css_task_iter_advance() from css_task_iter_next().  The
  new function whines if called on a terminated iterator.

Except for the termination check, this is pure reorganization and
doesn't introduce any behavior changes.  This will help the planned
locking update for css_task_iter.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent f6d7d049

kernel/cgroup.c

+28 −21
Original line number Diff line number Diff line
@@ -3793,12 +3793,12 @@ bool css_has_online_children(struct cgroup_subsys_state *css) 
}



/**

 * css_advance_task_iter - advance a task itererator to the next css_set

 * css_task_iter_advance_css_set - advance a task itererator to the next css_set

 * @it: the iterator to advance

 *

 * Advance @it to the next css_set to walk.

 */

static void css_advance_task_iter(struct css_task_iter *it)

static void css_task_iter_advance_css_set(struct css_task_iter *it)

{

	struct list_head *l = it->cset_pos;

	struct cgrp_cset_link *link;
@@ -3809,6 +3809,7 @@ static void css_advance_task_iter(struct css_task_iter *it) 
		l = l->next;

		if (l == it->cset_head) {

			it->cset_pos = NULL;

			it->task_pos = NULL;

			return;

		}
@@ -3832,6 +3833,28 @@ static void css_advance_task_iter(struct css_task_iter *it) 
	it->mg_tasks_head = &cset->mg_tasks;

}



static void css_task_iter_advance(struct css_task_iter *it)

{

	struct list_head *l = it->task_pos;



	WARN_ON_ONCE(!l);



	/*

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

	 * first and then ->mg_tasks.  After ->mg_tasks, we move onto the

	 * next cset.

	 */

	l = l->next;



	if (l == it->tasks_head)

		l = it->mg_tasks_head->next;



	if (l == it->mg_tasks_head)

		css_task_iter_advance_css_set(it);

	else

		it->task_pos = l;

}



/**

 * css_task_iter_start - initiate task iteration

 * @css: the css to walk tasks of
@@ -3864,7 +3887,7 @@ void css_task_iter_start(struct cgroup_subsys_state *css, 


	it->cset_head = it->cset_pos;



	css_advance_task_iter(it);

	css_task_iter_advance_css_set(it);

}



/**
@@ -3878,28 +3901,12 @@ void css_task_iter_start(struct cgroup_subsys_state *css, 
struct task_struct *css_task_iter_next(struct css_task_iter *it)

{

	struct task_struct *res;

	struct list_head *l = it->task_pos;



	/* If the iterator cg is NULL, we have no tasks */

	if (!it->cset_pos)

		return NULL;

	res = list_entry(l, struct task_struct, cg_list);



	/*

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

	 * first and then ->mg_tasks.  After ->mg_tasks, we move onto the

	 * next cset.

	 */

	l = l->next;



	if (l == it->tasks_head)

		l = it->mg_tasks_head->next;



	if (l == it->mg_tasks_head)

		css_advance_task_iter(it);

	else

		it->task_pos = l;



	res = list_entry(it->task_pos, struct task_struct, cg_list);

	css_task_iter_advance(it);

	return res;

}