static_call: Fix return type of static_call_init

Functions that are passed to early_initcall should be of type
initcall_t, which expects a return type of int. This is not currently an
error but a patch in the Clang LTO series could change that in the
future.

Fixes: 9183c3f ("static_call: Add inline static call infrastructure")
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/lkml/20200903203053.3411268-17-samitolvanen@google.com/

Author: nathanchance

include/linux/static_call.h

@@ -136,7 +136,7 @@ extern void arch_static_call_transform(void *site, void *tramp, void *func, bool
 
 #ifdef CONFIG_HAVE_STATIC_CALL_INLINE
 
-extern void __init static_call_init(void);
+extern int __init static_call_init(void);
 
 struct static_call_mod {
 	struct static_call_mod *next;
@@ -187,7 +187,7 @@ extern int static_call_text_reserved(void *start, void *end);
 
 #elif defined(CONFIG_HAVE_STATIC_CALL)
 
-static inline void static_call_init(void) { }
+static inline int static_call_init(void) { return 0; }
 
 struct static_call_key {
 	void *func;
@@ -234,7 +234,7 @@ static inline int static_call_text_reserved(void *start, void *end)
 
 #else /* Generic implementation */
 
-static inline void static_call_init(void) { }
+static inline int static_call_init(void) { return 0; }
 
 struct static_call_key {
 	void *func;

kernel/static_call.c

@@ -410,12 +410,12 @@ int static_call_text_reserved(void *start, void *end)
 	return __static_call_mod_text_reserved(start, end);
 }
 
-void __init static_call_init(void)
+int __init static_call_init(void)
 {
 	int ret;
 
 	if (static_call_initialized)
-		return;
+		return 0;
 
 	cpus_read_lock();
 	static_call_lock();
@@ -434,6 +434,7 @@ void __init static_call_init(void)
 #ifdef CONFIG_MODULES
 	register_module_notifier(&static_call_module_nb);
 #endif
+	return 0;
 }
 early_initcall(static_call_init);