Implement trivial cgroup_has_tasks() which tests whether
cgrp->nr_populated_csets is zero and replace the explicit local
populated test in cgroup_subtree_control(). This simplifies the code
and cgroup_has_tasks() will be used in more places later.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
Applying to cgroup/for-4.14.
Thanks.
kernel/cgroup/cgroup.c | 30 ++++++++----------------------
1 file changed, 8 insertions(+), 22 deletions(-)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -325,6 +325,11 @@ static struct cgroup *cgroup_parent(stru
return NULL;
}
+static bool cgroup_has_tasks(struct cgroup *cgrp)
+{
+ return cgrp->nr_populated_csets;
+}
+
/* subsystems visibly enabled on a cgroup */
static u16 cgroup_control(struct cgroup *cgrp)
{
@@ -2971,28 +2976,9 @@ static ssize_t cgroup_subtree_control_wr
* Except for the root, subtree_control must be zero for a cgroup
* with tasks so that child cgroups don't compete against tasks.
*/
- if (enable && cgroup_parent(cgrp)) {
- struct cgrp_cset_link *link;
-
- /*
- * Because namespaces pin csets too, @cgrp->cset_links
- * might not be empty even when @cgrp is empty. Walk and
- * verify each cset.
- */
- spin_lock_irq(&css_set_lock);
-
- ret = 0;
- list_for_each_entry(link, &cgrp->cset_links, cset_link) {
- if (css_set_populated(link->cset)) {
- ret = -EBUSY;
- break;
- }
- }
-
- spin_unlock_irq(&css_set_lock);
-
- if (ret)
- goto out_unlock;
+ if (enable && cgroup_parent(cgrp) && cgroup_has_tasks(cgrp)) {
+ ret = -EBUSY;
+ goto out_unlock;
}
/* save and update control masks and prepare csses */
--
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