[PATCH] printk: fix _entry_ptr build warning

[Chunhui Li]

We build with Werror and suffer build error when
enable CONFIG_PRINTK_INDEX, such as
gfp.h:223:2: error: unused variable '_entry_ptr'
ratelimit.h:31:3: error: unused variable '_entry_ptr'
kallsyms.h:172:2: error: unused variable '_entry_ptr'
[-Werror,-Wunused-variable]

Fix the warning by appending __attribute__((unused)).

Signed-off-by: Chunhui Li <chunhui.li@xxxxxxxxxxxx>
---
 include/linux/printk.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 8ef499ab3c1e..749c1c4257f1 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -392,7 +392,7 @@ struct pi_entry {
 				.level = __builtin_constant_p(_level) ? (_level) : NULL, \
 				.subsys_fmt_prefix = _subsys_fmt_prefix,\
 			};						\
-			static const struct pi_entry *_entry_ptr	\
+			static const struct pi_entry *_entry_ptr __attribute__((unused)) \
 			__used __section(".printk_index") = &_entry;	\
 		}							\
 	} while (0)
-- 
2.18.0