[PATCH] printk: Make multiple inclusion of kernel/printk/internal.h safe

[Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>]

kernel test robot reported that kernel/printk/internal.h is not ready
to be #include'd for multiple times, and that vprintk_func() for
CONFIG_PRINTK=n should be marked as "static inline".

Since "tty: use printk_safe context at tty_msg()" will make
kernel/printk/internal.h be #include'd for multiple times, let's fix
this problem first.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 099f1c84c0052ec1 ("printk: introduce per-cpu safe_print seq buffer")
Cc: <stable@vger.kernel.org> # 4.11+
---
 kernel/printk/internal.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 3a8fd491758c..2119c546cba2 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -2,6 +2,10 @@
 /*
  * internal.h - printk internal definitions
  */
+
+#ifndef _KERNEL_PRINTK_INTERNAL_H
+#define _KERNEL_PRINTK_INTERNAL_H
+
 #include <linux/percpu.h>
 
 #ifdef CONFIG_PRINTK
@@ -56,7 +60,7 @@ void defer_console_output(void);
 
 #else
 
-__printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; }
+static inline __printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; }
 
 /*
  * In !PRINTK builds we still export logbuf_lock spin_lock, console_sem
@@ -72,3 +76,5 @@ __printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; }
 static inline void printk_safe_init(void) { }
 static inline bool printk_percpu_data_ready(void) { return false; }
 #endif /* CONFIG_PRINTK */
+
+#endif
-- 
2.18.4