v4.19.13 snapshot.
diff --git a/include/linux/task_work.h b/include/linux/task_work.h
new file mode 100644
index 0000000..bd9a6a9
--- /dev/null
+++ b/include/linux/task_work.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_TASK_WORK_H
+#define _LINUX_TASK_WORK_H
+
+#include <linux/list.h>
+#include <linux/sched.h>
+
+typedef void (*task_work_func_t)(struct callback_head *);
+
+static inline void
+init_task_work(struct callback_head *twork, task_work_func_t func)
+{
+ twork->func = func;
+}
+
+int task_work_add(struct task_struct *task, struct callback_head *twork, bool);
+struct callback_head *task_work_cancel(struct task_struct *, task_work_func_t);
+void task_work_run(void);
+
+static inline void exit_task_work(struct task_struct *task)
+{
+ task_work_run();
+}
+
+#endif /* _LINUX_TASK_WORK_H */