Merge tag 'v5.2-rc6' into asoc-5.3

Linux 5.2-rc6

1 files changed, 12 insertions, 2 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c0077adeea83..0297f930a56e 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -43,6 +43,9 @@
 /* walk all threaded css_sets in the domain */
 #define CSS_TASK_ITER_THREADED		(1U << 1)
 
+/* internal flags */
+#define CSS_TASK_ITER_SKIPPED		(1U << 16)
+
 /* a css_task_iter should be treated as an opaque object */
 struct css_task_iter {
 	struct cgroup_subsys		*ss;
@@ -57,6 +60,7 @@ struct css_task_iter {
 	struct list_head		*task_pos;
 	struct list_head		*tasks_head;
 	struct list_head		*mg_tasks_head;
+	struct list_head		*dying_tasks_head;
 
 	struct css_set			*cur_cset;
 	struct css_set			*cur_dcset;
@@ -487,7 +491,7 @@ static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
  *
  * Find the css for the (@task, @subsys_id) combination, increment a
  * reference on and return it.  This function is guaranteed to return a
- * valid css.
+ * valid css.  The returned css may already have been offlined.
  */
 static inline struct cgroup_subsys_state *
 task_get_css(struct task_struct *task, int subsys_id)
@@ -497,7 +501,13 @@ task_get_css(struct task_struct *task, int subsys_id)
 	rcu_read_lock();
 	while (true) {
 		css = task_css(task, subsys_id);
-		if (likely(css_tryget_online(css)))
+		/*
+		 * Can't use css_tryget_online() here.  A task which has
+		 * PF_EXITING set may stay associated with an offline css.
+		 * If such task calls this function, css_tryget_online()
+		 * will keep failing.
+		 */
+		if (likely(css_tryget(css)))
 			break;
 		cpu_relax();
 	}