kthread: add __printf attributes

When commit fbae2d44aa1d ("kthread: add kthread_create_worker*()")
introduced some kthread_create_...() functions which were taking
printf-like parametter, it introduced __printf attributes to some
functions (e.g.  kthread_create_worker()).  Nevertheless some new
functions were forgotten (they have been detected thanks to
-Wmissing-format-attribute warning flag).

Add the missing __printf attributes to the newly-introduced functions in
order to detect formatting issues at build-time with -Wformat flag.

Link: http://lkml.kernel.org/r/20161126193543.22672-1-nicolas.iooss_linux@m4x.org
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kthread.h

@@ -175,7 +175,7 @@ __printf(2, 3)
 struct kthread_worker *
 kthread_create_worker(unsigned int flags, const char namefmt[], ...);
 
-struct kthread_worker *
+__printf(3, 4) struct kthread_worker *
 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
 			     const char namefmt[], ...);
 

kernel/kthread.c

@@ -261,7 +261,8 @@ static void create_kthread(struct kthread_create_info *create)
 	}
 }
 
-static struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
+static __printf(4, 0)
+struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
 						    void *data, int node,
 						    const char namefmt[],
 						    va_list args)
@@ -635,7 +636,7 @@ repeat:
 }
 EXPORT_SYMBOL_GPL(kthread_worker_fn);
 
-static struct kthread_worker *
+static __printf(3, 0) struct kthread_worker *
 __kthread_create_worker(int cpu, unsigned int flags,
 			const char namefmt[], va_list args)
 {