v4.19.13 snapshot.
diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h
new file mode 100644
index 0000000..6fd615a
--- /dev/null
+++ b/include/linux/rtmutex.h
@@ -0,0 +1,125 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * RT Mutexes: blocking mutual exclusion locks with PI support
+ *
+ * started by Ingo Molnar and Thomas Gleixner:
+ *
+ * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ * Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
+ *
+ * This file contains the public data structure and API definitions.
+ */
+
+#ifndef __LINUX_RT_MUTEX_H
+#define __LINUX_RT_MUTEX_H
+
+#include <linux/linkage.h>
+#include <linux/rbtree.h>
+#include <linux/spinlock_types.h>
+
+extern int max_lock_depth; /* for sysctl */
+
+/**
+ * The rt_mutex structure
+ *
+ * @wait_lock: spinlock to protect the structure
+ * @waiters: rbtree root to enqueue waiters in priority order;
+ * caches top-waiter (leftmost node).
+ * @owner: the mutex owner
+ */
+struct rt_mutex {
+ raw_spinlock_t wait_lock;
+ struct rb_root_cached waiters;
+ struct task_struct *owner;
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+ int save_state;
+ const char *name, *file;
+ int line;
+ void *magic;
+#endif
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lockdep_map dep_map;
+#endif
+};
+
+struct rt_mutex_waiter;
+struct hrtimer_sleeper;
+
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+ extern int rt_mutex_debug_check_no_locks_freed(const void *from,
+ unsigned long len);
+ extern void rt_mutex_debug_check_no_locks_held(struct task_struct *task);
+#else
+ static inline int rt_mutex_debug_check_no_locks_freed(const void *from,
+ unsigned long len)
+ {
+ return 0;
+ }
+# define rt_mutex_debug_check_no_locks_held(task) do { } while (0)
+#endif
+
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+# define __DEBUG_RT_MUTEX_INITIALIZER(mutexname) \
+ , .name = #mutexname, .file = __FILE__, .line = __LINE__
+
+# define rt_mutex_init(mutex) \
+do { \
+ static struct lock_class_key __key; \
+ __rt_mutex_init(mutex, __func__, &__key); \
+} while (0)
+
+ extern void rt_mutex_debug_task_free(struct task_struct *tsk);
+#else
+# define __DEBUG_RT_MUTEX_INITIALIZER(mutexname)
+# define rt_mutex_init(mutex) __rt_mutex_init(mutex, NULL, NULL)
+# define rt_mutex_debug_task_free(t) do { } while (0)
+#endif
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#define __DEP_MAP_RT_MUTEX_INITIALIZER(mutexname) \
+ , .dep_map = { .name = #mutexname }
+#else
+#define __DEP_MAP_RT_MUTEX_INITIALIZER(mutexname)
+#endif
+
+#define __RT_MUTEX_INITIALIZER(mutexname) \
+ { .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(mutexname.wait_lock) \
+ , .waiters = RB_ROOT_CACHED \
+ , .owner = NULL \
+ __DEBUG_RT_MUTEX_INITIALIZER(mutexname) \
+ __DEP_MAP_RT_MUTEX_INITIALIZER(mutexname)}
+
+#define DEFINE_RT_MUTEX(mutexname) \
+ struct rt_mutex mutexname = __RT_MUTEX_INITIALIZER(mutexname)
+
+/**
+ * rt_mutex_is_locked - is the mutex locked
+ * @lock: the mutex to be queried
+ *
+ * Returns 1 if the mutex is locked, 0 if unlocked.
+ */
+static inline int rt_mutex_is_locked(struct rt_mutex *lock)
+{
+ return lock->owner != NULL;
+}
+
+extern void __rt_mutex_init(struct rt_mutex *lock, const char *name, struct lock_class_key *key);
+extern void rt_mutex_destroy(struct rt_mutex *lock);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+extern void rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass);
+#define rt_mutex_lock(lock) rt_mutex_lock_nested(lock, 0)
+#else
+extern void rt_mutex_lock(struct rt_mutex *lock);
+#define rt_mutex_lock_nested(lock, subclass) rt_mutex_lock(lock)
+#endif
+
+extern int rt_mutex_lock_interruptible(struct rt_mutex *lock);
+extern int rt_mutex_timed_lock(struct rt_mutex *lock,
+ struct hrtimer_sleeper *timeout);
+
+extern int rt_mutex_trylock(struct rt_mutex *lock);
+
+extern void rt_mutex_unlock(struct rt_mutex *lock);
+
+#endif