v4.19.13 snapshot.
diff --git a/include/linux/rwsem-spinlock.h b/include/linux/rwsem-spinlock.h
new file mode 100644
index 0000000..e475683
--- /dev/null
+++ b/include/linux/rwsem-spinlock.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* rwsem-spinlock.h: fallback C implementation
+ *
+ * Copyright (c) 2001 David Howells (dhowells@redhat.com).
+ * - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de>
+ * - Derived also from comments by Linus
+ */
+
+#ifndef _LINUX_RWSEM_SPINLOCK_H
+#define _LINUX_RWSEM_SPINLOCK_H
+
+#ifndef _LINUX_RWSEM_H
+#error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
+#endif
+
+#ifdef __KERNEL__
+/*
+ * the rw-semaphore definition
+ * - if count is 0 then there are no active readers or writers
+ * - if count is +ve then that is the number of active readers
+ * - if count is -1 then there is one active writer
+ * - if wait_list is not empty, then there are processes waiting for the semaphore
+ */
+struct rw_semaphore {
+ __s32 count;
+ raw_spinlock_t wait_lock;
+ struct list_head wait_list;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lockdep_map dep_map;
+#endif
+};
+
+#define RWSEM_UNLOCKED_VALUE 0x00000000
+
+extern void __down_read(struct rw_semaphore *sem);
+extern int __must_check __down_read_killable(struct rw_semaphore *sem);
+extern int __down_read_trylock(struct rw_semaphore *sem);
+extern void __down_write(struct rw_semaphore *sem);
+extern int __must_check __down_write_killable(struct rw_semaphore *sem);
+extern int __down_write_trylock(struct rw_semaphore *sem);
+extern void __up_read(struct rw_semaphore *sem);
+extern void __up_write(struct rw_semaphore *sem);
+extern void __downgrade_write(struct rw_semaphore *sem);
+extern int rwsem_is_locked(struct rw_semaphore *sem);
+
+#endif /* __KERNEL__ */
+#endif /* _LINUX_RWSEM_SPINLOCK_H */