v4.19.13 snapshot.
diff --git a/include/linux/rwlock.h b/include/linux/rwlock.h
new file mode 100644
index 0000000..3dcd617
--- /dev/null
+++ b/include/linux/rwlock.h
@@ -0,0 +1,131 @@
+#ifndef __LINUX_RWLOCK_H
+#define __LINUX_RWLOCK_H
+
+#ifndef __LINUX_SPINLOCK_H
+# error "please don't include this file directly"
+#endif
+
+/*
+ * rwlock related methods
+ *
+ * split out from spinlock.h
+ *
+ * portions Copyright 2005, Red Hat, Inc., Ingo Molnar
+ * Released under the General Public License (GPL).
+ */
+
+#ifdef CONFIG_DEBUG_SPINLOCK
+ extern void __rwlock_init(rwlock_t *lock, const char *name,
+ struct lock_class_key *key);
+# define rwlock_init(lock) \
+do { \
+ static struct lock_class_key __key; \
+ \
+ __rwlock_init((lock), #lock, &__key); \
+} while (0)
+#else
+# define rwlock_init(lock) \
+ do { *(lock) = __RW_LOCK_UNLOCKED(lock); } while (0)
+#endif
+
+#ifdef CONFIG_DEBUG_SPINLOCK
+ extern void do_raw_read_lock(rwlock_t *lock) __acquires(lock);
+#define do_raw_read_lock_flags(lock, flags) do_raw_read_lock(lock)
+ extern int do_raw_read_trylock(rwlock_t *lock);
+ extern void do_raw_read_unlock(rwlock_t *lock) __releases(lock);
+ extern void do_raw_write_lock(rwlock_t *lock) __acquires(lock);
+#define do_raw_write_lock_flags(lock, flags) do_raw_write_lock(lock)
+ extern int do_raw_write_trylock(rwlock_t *lock);
+ extern void do_raw_write_unlock(rwlock_t *lock) __releases(lock);
+#else
+
+#ifndef arch_read_lock_flags
+# define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
+#endif
+
+#ifndef arch_write_lock_flags
+# define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
+#endif
+
+# define do_raw_read_lock(rwlock) do {__acquire(lock); arch_read_lock(&(rwlock)->raw_lock); } while (0)
+# define do_raw_read_lock_flags(lock, flags) \
+ do {__acquire(lock); arch_read_lock_flags(&(lock)->raw_lock, *(flags)); } while (0)
+# define do_raw_read_trylock(rwlock) arch_read_trylock(&(rwlock)->raw_lock)
+# define do_raw_read_unlock(rwlock) do {arch_read_unlock(&(rwlock)->raw_lock); __release(lock); } while (0)
+# define do_raw_write_lock(rwlock) do {__acquire(lock); arch_write_lock(&(rwlock)->raw_lock); } while (0)
+# define do_raw_write_lock_flags(lock, flags) \
+ do {__acquire(lock); arch_write_lock_flags(&(lock)->raw_lock, *(flags)); } while (0)
+# define do_raw_write_trylock(rwlock) arch_write_trylock(&(rwlock)->raw_lock)
+# define do_raw_write_unlock(rwlock) do {arch_write_unlock(&(rwlock)->raw_lock); __release(lock); } while (0)
+#endif
+
+/*
+ * Define the various rw_lock methods. Note we define these
+ * regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The various
+ * methods are defined as nops in the case they are not required.
+ */
+#define read_trylock(lock) __cond_lock(lock, _raw_read_trylock(lock))
+#define write_trylock(lock) __cond_lock(lock, _raw_write_trylock(lock))
+
+#define write_lock(lock) _raw_write_lock(lock)
+#define read_lock(lock) _raw_read_lock(lock)
+
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+
+#define read_lock_irqsave(lock, flags) \
+ do { \
+ typecheck(unsigned long, flags); \
+ flags = _raw_read_lock_irqsave(lock); \
+ } while (0)
+#define write_lock_irqsave(lock, flags) \
+ do { \
+ typecheck(unsigned long, flags); \
+ flags = _raw_write_lock_irqsave(lock); \
+ } while (0)
+
+#else
+
+#define read_lock_irqsave(lock, flags) \
+ do { \
+ typecheck(unsigned long, flags); \
+ _raw_read_lock_irqsave(lock, flags); \
+ } while (0)
+#define write_lock_irqsave(lock, flags) \
+ do { \
+ typecheck(unsigned long, flags); \
+ _raw_write_lock_irqsave(lock, flags); \
+ } while (0)
+
+#endif
+
+#define read_lock_irq(lock) _raw_read_lock_irq(lock)
+#define read_lock_bh(lock) _raw_read_lock_bh(lock)
+#define write_lock_irq(lock) _raw_write_lock_irq(lock)
+#define write_lock_bh(lock) _raw_write_lock_bh(lock)
+#define read_unlock(lock) _raw_read_unlock(lock)
+#define write_unlock(lock) _raw_write_unlock(lock)
+#define read_unlock_irq(lock) _raw_read_unlock_irq(lock)
+#define write_unlock_irq(lock) _raw_write_unlock_irq(lock)
+
+#define read_unlock_irqrestore(lock, flags) \
+ do { \
+ typecheck(unsigned long, flags); \
+ _raw_read_unlock_irqrestore(lock, flags); \
+ } while (0)
+#define read_unlock_bh(lock) _raw_read_unlock_bh(lock)
+
+#define write_unlock_irqrestore(lock, flags) \
+ do { \
+ typecheck(unsigned long, flags); \
+ _raw_write_unlock_irqrestore(lock, flags); \
+ } while (0)
+#define write_unlock_bh(lock) _raw_write_unlock_bh(lock)
+
+#define write_trylock_irqsave(lock, flags) \
+({ \
+ local_irq_save(flags); \
+ write_trylock(lock) ? \
+ 1 : ({ local_irq_restore(flags); 0; }); \
+})
+
+#endif /* __LINUX_RWLOCK_H */