[PATCH v3 2/7] cgroup: implement __cgroup_task_count() helper

Roman Gushchin
2018-11-17T00:38:42Z

The helper is identical to the existing cgroup_task_count()
except it doesn't take the css_set_lock by itself, assuming
that the caller does.

Also, move cgroup_task_count() implementation into
kernel/cgroup/cgroup.c, as there is nothing specific to cgroup v1.

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: kernel-team@fb.com
---
kernel/cgroup/cgroup-internal.h | 1 +
kernel/cgroup/cgroup-v1.c | 16 ----------------
kernel/cgroup/cgroup.c | 33 +++++++++++++++++++++++++++++++++
3 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index 75568fcf2180..fe01a9fa4a8d 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -224,6 +224,7 @@ int cgroup_rmdir(struct kernfs_node *kn);
int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
struct kernfs_root *kf_root);

+int __cgroup_task_count(const struct cgroup *cgrp);
int cgroup_task_count(const struct cgroup *cgrp);

/*
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 51063e7a93c2..6134fef07d57 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -336,22 +336,6 @@ static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
return l;
}

-/**
- * cgroup_task_count - count the number of tasks in a cgroup.
- * @cgrp: the cgroup in question
- */
-int cgroup_task_count(const struct cgroup *cgrp)
-{
- int count = 0;
- struct cgrp_cset_link *link;
-
- spin_lock_irq(&css_set_lock);
- list_for_each_entry(link, &cgrp->cset_links, cset_link)
- count += link->cset->nr_tasks;
- spin_unlock_irq(&css_set_lock);
- return count;
-}
-
/*
* Load a cgroup's pidarray with either procs' tgids or tasks' pids
*/
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 4a3dae2a8283..ef3442555b32 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -561,6 +561,39 @@ static void cgroup_get_live(struct cgroup *cgrp)
css_get(&cgrp->self);
}

+/**
+ * __cgroup_task_count - count the number of tasks in a cgroup. The caller
+ * is responsible for taking the css_set_lock.
+ * @cgrp: the cgroup in question
+ */
+int __cgroup_task_count(const struct cgroup *cgrp)
+{
+ int count = 0;
+ struct cgrp_cset_link *link;
+
+ lockdep_assert_held(&css_set_lock);
+
+ list_for_each_entry(link, &cgrp->cset_links, cset_link)
+ count += link->cset->nr_tasks;
+
+ return count;
+}
+
+/**
+ * cgroup_task_count - count the number of tasks in a cgroup.
+ * @cgrp: the cgroup in question
+ */
+int cgroup_task_count(const struct cgroup *cgrp)
+{
+ int count;
+
+ spin_lock_irq(&css_set_lock);
+ count = __cgroup_task_count(cgrp);
+ spin_unlock_irq(&css_set_lock);
+
+ return count;
+}
+
struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
{
struct cgroup *cgrp = of->kn->parent->priv;
--
2.17.2