jump-label: initialize jump-label subsystem much earlier

Initialize jump_labels much, much earlier, so they're available for use
during system setup.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

include/linux/jump_label.h

@@ -16,7 +16,7 @@ struct jump_label_key {
 
 # include <asm/jump_label.h>
 # define HAVE_JUMP_LABEL
-#endif
+#endif	/* CC_HAVE_ASM_GOTO && CONFIG_JUMP_LABEL */
 
 enum jump_label_type {
 	JUMP_LABEL_DISABLE = 0,
@@ -41,6 +41,7 @@ static __always_inline bool static_branch(struct jump_label_key *key)
 extern struct jump_entry __start___jump_table[];
 extern struct jump_entry __stop___jump_table[];
 
+extern void jump_label_init(void);
 extern void jump_label_lock(void);
 extern void jump_label_unlock(void);
 extern void arch_jump_label_transform(struct jump_entry *entry,
@@ -53,7 +54,7 @@ extern void jump_label_dec(struct jump_label_key *key);
 extern bool jump_label_enabled(struct jump_label_key *key);
 extern void jump_label_apply_nops(struct module *mod);
 
-#else
+#else  /* !HAVE_JUMP_LABEL */
 
 #include <linux/atomic.h>
 
@@ -63,6 +64,10 @@ struct jump_label_key {
 	atomic_t enabled;
 };
 
+static __always_inline void jump_label_init(void)
+{
+}
+
 static __always_inline bool static_branch(struct jump_label_key *key)
 {
 	if (unlikely(atomic_read(&key->enabled)))
@@ -97,7 +102,6 @@ static inline int jump_label_apply_nops(struct module *mod)
 {
 	return 0;
 }
+#endif	/* HAVE_JUMP_LABEL */
 
-#endif
-
-#endif
+#endif	/* _LINUX_JUMP_LABEL_H */

init/main.c

@@ -515,6 +515,9 @@ asmlinkage void __init start_kernel(void)
 	parse_args("Booting kernel", static_command_line, __start___param,
 		   __stop___param - __start___param,
 		   &unknown_bootoption);
+
+	jump_label_init();
+
 	/*
 	 * These use large bootmem allocations and must precede
 	 * kmem_cache_init()

kernel/jump_label.c

@@ -133,7 +133,7 @@ static void __jump_label_update(struct jump_label_key *key,
 	}
 }
 
-static __init int jump_label_init(void)
+void __init jump_label_init(void)
 {
 	struct jump_entry *iter_start = __start___jump_table;
 	struct jump_entry *iter_stop = __stop___jump_table;
@@ -159,10 +159,7 @@ static __init int jump_label_init(void)
 #endif
 	}
 	jump_label_unlock();
-
-	return 0;
 }
-early_initcall(jump_label_init);
 
 #ifdef CONFIG_MODULES