v4.19.13 snapshot.
diff --git a/include/linux/kthread.h b/include/linux/kthread.h
new file mode 100644
index 0000000..c196176
--- /dev/null
+++ b/include/linux/kthread.h
@@ -0,0 +1,211 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_KTHREAD_H
+#define _LINUX_KTHREAD_H
+/* Simple interface for creating and stopping kernel threads without mess. */
+#include <linux/err.h>
+#include <linux/sched.h>
+#include <linux/cgroup.h>
+
+__printf(4, 5)
+struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
+ void *data,
+ int node,
+ const char namefmt[], ...);
+
+/**
+ * kthread_create - create a kthread on the current node
+ * @threadfn: the function to run in the thread
+ * @data: data pointer for @threadfn()
+ * @namefmt: printf-style format string for the thread name
+ * @arg...: arguments for @namefmt.
+ *
+ * This macro will create a kthread on the current node, leaving it in
+ * the stopped state. This is just a helper for kthread_create_on_node();
+ * see the documentation there for more details.
+ */
+#define kthread_create(threadfn, data, namefmt, arg...) \
+ kthread_create_on_node(threadfn, data, NUMA_NO_NODE, namefmt, ##arg)
+
+
+struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
+ void *data,
+ unsigned int cpu,
+ const char *namefmt);
+
+/**
+ * kthread_run - create and wake a thread.
+ * @threadfn: the function to run until signal_pending(current).
+ * @data: data ptr for @threadfn.
+ * @namefmt: printf-style name for the thread.
+ *
+ * Description: Convenient wrapper for kthread_create() followed by
+ * wake_up_process(). Returns the kthread or ERR_PTR(-ENOMEM).
+ */
+#define kthread_run(threadfn, data, namefmt, ...) \
+({ \
+ struct task_struct *__k \
+ = kthread_create(threadfn, data, namefmt, ## __VA_ARGS__); \
+ if (!IS_ERR(__k)) \
+ wake_up_process(__k); \
+ __k; \
+})
+
+void free_kthread_struct(struct task_struct *k);
+void kthread_bind(struct task_struct *k, unsigned int cpu);
+void kthread_bind_mask(struct task_struct *k, const struct cpumask *mask);
+int kthread_stop(struct task_struct *k);
+bool kthread_should_stop(void);
+bool kthread_should_park(void);
+bool kthread_freezable_should_stop(bool *was_frozen);
+void *kthread_data(struct task_struct *k);
+void *kthread_probe_data(struct task_struct *k);
+int kthread_park(struct task_struct *k);
+void kthread_unpark(struct task_struct *k);
+void kthread_parkme(void);
+
+int kthreadd(void *unused);
+extern struct task_struct *kthreadd_task;
+extern int tsk_fork_get_node(struct task_struct *tsk);
+
+/*
+ * Simple work processor based on kthread.
+ *
+ * This provides easier way to make use of kthreads. A kthread_work
+ * can be queued and flushed using queue/kthread_flush_work()
+ * respectively. Queued kthread_works are processed by a kthread
+ * running kthread_worker_fn().
+ */
+struct kthread_work;
+typedef void (*kthread_work_func_t)(struct kthread_work *work);
+void kthread_delayed_work_timer_fn(struct timer_list *t);
+
+enum {
+ KTW_FREEZABLE = 1 << 0, /* freeze during suspend */
+};
+
+struct kthread_worker {
+ unsigned int flags;
+ spinlock_t lock;
+ struct list_head work_list;
+ struct list_head delayed_work_list;
+ struct task_struct *task;
+ struct kthread_work *current_work;
+};
+
+struct kthread_work {
+ struct list_head node;
+ kthread_work_func_t func;
+ struct kthread_worker *worker;
+ /* Number of canceling calls that are running at the moment. */
+ int canceling;
+};
+
+struct kthread_delayed_work {
+ struct kthread_work work;
+ struct timer_list timer;
+};
+
+#define KTHREAD_WORKER_INIT(worker) { \
+ .lock = __SPIN_LOCK_UNLOCKED((worker).lock), \
+ .work_list = LIST_HEAD_INIT((worker).work_list), \
+ .delayed_work_list = LIST_HEAD_INIT((worker).delayed_work_list),\
+ }
+
+#define KTHREAD_WORK_INIT(work, fn) { \
+ .node = LIST_HEAD_INIT((work).node), \
+ .func = (fn), \
+ }
+
+#define KTHREAD_DELAYED_WORK_INIT(dwork, fn) { \
+ .work = KTHREAD_WORK_INIT((dwork).work, (fn)), \
+ .timer = __TIMER_INITIALIZER(kthread_delayed_work_timer_fn,\
+ TIMER_IRQSAFE), \
+ }
+
+#define DEFINE_KTHREAD_WORKER(worker) \
+ struct kthread_worker worker = KTHREAD_WORKER_INIT(worker)
+
+#define DEFINE_KTHREAD_WORK(work, fn) \
+ struct kthread_work work = KTHREAD_WORK_INIT(work, fn)
+
+#define DEFINE_KTHREAD_DELAYED_WORK(dwork, fn) \
+ struct kthread_delayed_work dwork = \
+ KTHREAD_DELAYED_WORK_INIT(dwork, fn)
+
+/*
+ * kthread_worker.lock needs its own lockdep class key when defined on
+ * stack with lockdep enabled. Use the following macros in such cases.
+ */
+#ifdef CONFIG_LOCKDEP
+# define KTHREAD_WORKER_INIT_ONSTACK(worker) \
+ ({ kthread_init_worker(&worker); worker; })
+# define DEFINE_KTHREAD_WORKER_ONSTACK(worker) \
+ struct kthread_worker worker = KTHREAD_WORKER_INIT_ONSTACK(worker)
+#else
+# define DEFINE_KTHREAD_WORKER_ONSTACK(worker) DEFINE_KTHREAD_WORKER(worker)
+#endif
+
+extern void __kthread_init_worker(struct kthread_worker *worker,
+ const char *name, struct lock_class_key *key);
+
+#define kthread_init_worker(worker) \
+ do { \
+ static struct lock_class_key __key; \
+ __kthread_init_worker((worker), "("#worker")->lock", &__key); \
+ } while (0)
+
+#define kthread_init_work(work, fn) \
+ do { \
+ memset((work), 0, sizeof(struct kthread_work)); \
+ INIT_LIST_HEAD(&(work)->node); \
+ (work)->func = (fn); \
+ } while (0)
+
+#define kthread_init_delayed_work(dwork, fn) \
+ do { \
+ kthread_init_work(&(dwork)->work, (fn)); \
+ __init_timer(&(dwork)->timer, \
+ kthread_delayed_work_timer_fn, \
+ TIMER_IRQSAFE); \
+ } while (0)
+
+int kthread_worker_fn(void *worker_ptr);
+
+__printf(2, 3)
+struct kthread_worker *
+kthread_create_worker(unsigned int flags, const char namefmt[], ...);
+
+__printf(3, 4) struct kthread_worker *
+kthread_create_worker_on_cpu(int cpu, unsigned int flags,
+ const char namefmt[], ...);
+
+bool kthread_queue_work(struct kthread_worker *worker,
+ struct kthread_work *work);
+
+bool kthread_queue_delayed_work(struct kthread_worker *worker,
+ struct kthread_delayed_work *dwork,
+ unsigned long delay);
+
+bool kthread_mod_delayed_work(struct kthread_worker *worker,
+ struct kthread_delayed_work *dwork,
+ unsigned long delay);
+
+void kthread_flush_work(struct kthread_work *work);
+void kthread_flush_worker(struct kthread_worker *worker);
+
+bool kthread_cancel_work_sync(struct kthread_work *work);
+bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *work);
+
+void kthread_destroy_worker(struct kthread_worker *worker);
+
+#ifdef CONFIG_BLK_CGROUP
+void kthread_associate_blkcg(struct cgroup_subsys_state *css);
+struct cgroup_subsys_state *kthread_blkcg(void);
+#else
+static inline void kthread_associate_blkcg(struct cgroup_subsys_state *css) { }
+static inline struct cgroup_subsys_state *kthread_blkcg(void)
+{
+ return NULL;
+}
+#endif
+#endif /* _LINUX_KTHREAD_H */