v4.19.13 snapshot.
diff --git a/include/linux/spinlock_up.h b/include/linux/spinlock_up.h
new file mode 100644
index 0000000..0ac9112
--- /dev/null
+++ b/include/linux/spinlock_up.h
@@ -0,0 +1,72 @@
+#ifndef __LINUX_SPINLOCK_UP_H
+#define __LINUX_SPINLOCK_UP_H
+
+#ifndef __LINUX_SPINLOCK_H
+# error "please don't include this file directly"
+#endif
+
+#include <asm/processor.h> /* for cpu_relax() */
+#include <asm/barrier.h>
+
+/*
+ * include/linux/spinlock_up.h - UP-debug version of spinlocks.
+ *
+ * portions Copyright 2005, Red Hat, Inc., Ingo Molnar
+ * Released under the General Public License (GPL).
+ *
+ * In the debug case, 1 means unlocked, 0 means locked. (the values
+ * are inverted, to catch initialization bugs)
+ *
+ * No atomicity anywhere, we are on UP. However, we still need
+ * the compiler barriers, because we do not want the compiler to
+ * move potentially faulting instructions (notably user accesses)
+ * into the locked sequence, resulting in non-atomic execution.
+ */
+
+#ifdef CONFIG_DEBUG_SPINLOCK
+#define arch_spin_is_locked(x) ((x)->slock == 0)
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+ lock->slock = 0;
+ barrier();
+}
+
+static inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+ char oldval = lock->slock;
+
+ lock->slock = 0;
+ barrier();
+
+ return oldval > 0;
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+ barrier();
+ lock->slock = 1;
+}
+
+/*
+ * Read-write spinlocks. No debug version.
+ */
+#define arch_read_lock(lock) do { barrier(); (void)(lock); } while (0)
+#define arch_write_lock(lock) do { barrier(); (void)(lock); } while (0)
+#define arch_read_trylock(lock) ({ barrier(); (void)(lock); 1; })
+#define arch_write_trylock(lock) ({ barrier(); (void)(lock); 1; })
+#define arch_read_unlock(lock) do { barrier(); (void)(lock); } while (0)
+#define arch_write_unlock(lock) do { barrier(); (void)(lock); } while (0)
+
+#else /* DEBUG_SPINLOCK */
+#define arch_spin_is_locked(lock) ((void)(lock), 0)
+/* for sched/core.c and kernel_lock.c: */
+# define arch_spin_lock(lock) do { barrier(); (void)(lock); } while (0)
+# define arch_spin_lock_flags(lock, flags) do { barrier(); (void)(lock); } while (0)
+# define arch_spin_unlock(lock) do { barrier(); (void)(lock); } while (0)
+# define arch_spin_trylock(lock) ({ barrier(); (void)(lock); 1; })
+#endif /* DEBUG_SPINLOCK */
+
+#define arch_spin_is_contended(lock) (((void)(lock), 0))
+
+#endif /* __LINUX_SPINLOCK_UP_H */