linux-kernel - [PATCH] tracing: avoid build warning with HAVE_NOP

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Date:   Wed, 5 Jun 2019 13:11:58 +0200
From:   Vasily Gorbik <gor@...ux.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] tracing: avoid build warning with HAVE_NOP_MCOUNT

Selecting HAVE_NOP_MCOUNT enables -mnop-mcount (if gcc supports it)
and sets CC_USING_NOP_MCOUNT. Reuse __is_defined (which is suitable for
testing CC_USING_* defines) to avoid conditional compilation and fix
the following gcc 9 warning on s390:

kernel/trace/ftrace.c:2514:1: warning: ‘ftrace_code_disable’ defined
but not used [-Wunused-function]

Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
---
 kernel/trace/ftrace.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index a12aff849c04..e77a6c92620f 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2935,14 +2935,13 @@ static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs)
 			p = &pg->records[i];
 			p->flags = rec_flags;
 
-#ifndef CC_USING_NOP_MCOUNT
 			/*
 			 * Do the initial record conversion from mcount jump
 			 * to the NOP instructions.
 			 */
-			if (!ftrace_code_disable(mod, p))
+			if (!__is_defined(CC_USING_NOP_MCOUNT) &&
+			    !ftrace_code_disable(mod, p))
 				break;
-#endif
 
 			update_cnt++;
 		}
-- 
2.21.0