cgroup: kill and release paths serialize

Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org> Change-Id: Ibb30852f14b5e1cb6715eb30da7bbfbcd876c24b
tstruk · Jun 3, 2022 · c0f1b2f · c0f1b2f
1 parent 17d8e3d
commit c0f1b2f
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Showing 2 changed files with 21 additions and 3 deletions.
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
@@ -53,6 +53,8 @@ enum {
 	CSS_RELEASED	= (1 << 2), /* refcnt reached zero, released */
 	CSS_VISIBLE	= (1 << 3), /* css is visible to userland */
 	CSS_DYING	= (1 << 4), /* css is dying */
+	CSS_KILL_ENQED	= (1 << 5), /* css is dying */
+	CSS_NEED_RELESE	= (1 << 6), /* css is dying */
 };
 
 /* bits in struct cgroup flags field */

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
@@ -5210,8 +5210,14 @@ static void css_release(struct percpu_ref *ref)
 	struct cgroup_subsys_state *css =
 		container_of(ref, struct cgroup_subsys_state, refcnt);
 
-	INIT_WORK(&css->destroy_work, css_release_work_fn);
-	queue_work(cgroup_destroy_wq, &css->destroy_work);
+	if (!(css->flags & CSS_KILL_ENQED)) {
+printk("!!!! css_release css %llx release enqueue\n", css);
+		INIT_WORK(&css->destroy_work, css_release_work_fn);
+		queue_work(cgroup_destroy_wq, &css->destroy_work);
+	} else {
+printk("!!!! css_release css %llx release postopne\n", css);
+		css->flags |= CSS_NEED_RELESE;
+	}
 }
 
 static void init_and_link_css(struct cgroup_subsys_state *css,
@@ -5545,10 +5551,12 @@ int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
  */
 static void css_killed_work_fn(struct work_struct *work)
 {
-	struct cgroup_subsys_state *css =
+	struct cgroup_subsys_state *css_killed, *css =
 		container_of(work, struct cgroup_subsys_state, destroy_work);
 
 	mutex_lock(&cgroup_mutex);
+	css_killed = css;
+	css_killed->flags &= ~CSS_KILL_ENQED;
 
 	do {
 		offline_css(css);
@@ -5557,6 +5565,13 @@ static void css_killed_work_fn(struct work_struct *work)
 		css = css->parent;
 	} while (css && atomic_dec_and_test(&css->online_cnt));
 
+	if (css_killed->flags & CSS_NEED_RELESE) {
+printk("!!!! css_killed now releasing css %llx \n", css_killed);
+		INIT_WORK(&css_killed->destroy_work, css_release_work_fn);
+		queue_work(cgroup_destroy_wq, &css_killed->destroy_work);
+		css_killed->flags &= ~CSS_NEED_RELESE;
+	}
+
 	mutex_unlock(&cgroup_mutex);
 }
 
@@ -5567,6 +5582,7 @@ static void css_killed_ref_fn(struct percpu_ref *ref)
 		container_of(ref, struct cgroup_subsys_state, refcnt);
 
 	if (atomic_dec_and_test(&css->online_cnt)) {
+		css->flags |= CSS_KILL_ENQED;
 		INIT_WORK(&css->destroy_work, css_killed_work_fn);
 		queue_work(cgroup_destroy_wq, &css->destroy_work);
 	}