linux-kernel - [PATCH sysctl-next] ftrace: fix building with SYSCTL=n but DYNAMIC

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Date:   Fri, 15 Apr 2022 14:54:04 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     YueHaibing <yuehaibing@...wei.com>, mingo@...hat.com,
        xiaowei66@...wei.com, patches@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: [PATCH sysctl-next] ftrace: fix building with SYSCTL=n but
 DYNAMIC_FTRACE=y

One can enable dyanmic tracing but disable sysctls.
When this is doen we get the compile kernel warning:

  CC      kernel/trace/ftrace.o
kernel/trace/ftrace.c:3086:13: warning: ‘ftrace_shutdown_sysctl’ defined
but not used [-Wunused-function]
 3086 | static void ftrace_shutdown_sysctl(void)
      |             ^~~~~~~~~~~~~~~~~~~~~~
kernel/trace/ftrace.c:3068:13: warning: ‘ftrace_startup_sysctl’ defined
but not used [-Wunused-function]
 3068 | static void ftrace_startup_sysctl(void)

When CONFIG_DYNAMIC_FTRACE=n the ftrace_startup_sysctl() and
routines ftrace_shutdown_sysctl() still compiles, so these
are actually more just used for when SYSCTL=y.

Fix this then by just moving these routines to when sysctls
are enabled.

Fixes: 7cde53da38a3 ("ftrace: move sysctl_ftrace_enabled to ftrace.c")
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
---

Steven,

As with the other fixes I can take this in through sysctl-next if you
are OK with that, please let me know.

 kernel/trace/ftrace.c | 71 +++++++++++++++++++++----------------------
 1 file changed, 34 insertions(+), 37 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index db8d553728b6..d9424fd9a183 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3065,40 +3065,6 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command)
 	return 0;
 }
 
-static void ftrace_startup_sysctl(void)
-{
-	int command;
-
-	if (unlikely(ftrace_disabled))
-		return;
-
-	/* Force update next time */
-	saved_ftrace_func = NULL;
-	/* ftrace_start_up is true if we want ftrace running */
-	if (ftrace_start_up) {
-		command = FTRACE_UPDATE_CALLS;
-		if (ftrace_graph_active)
-			command |= FTRACE_START_FUNC_RET;
-		ftrace_startup_enable(command);
-	}
-}
-
-static void ftrace_shutdown_sysctl(void)
-{
-	int command;
-
-	if (unlikely(ftrace_disabled))
-		return;
-
-	/* ftrace_start_up is true if ftrace is running */
-	if (ftrace_start_up) {
-		command = FTRACE_DISABLE_CALLS;
-		if (ftrace_graph_active)
-			command |= FTRACE_STOP_FUNC_RET;
-		ftrace_run_update_code(command);
-	}
-}
-
 static u64		ftrace_update_time;
 unsigned long		ftrace_update_tot_cnt;
 unsigned long		ftrace_number_of_pages;
@@ -7267,9 +7233,6 @@ core_initcall(ftrace_nodyn_init);
 static inline int ftrace_init_dyn_tracefs(struct dentry *d_tracer) { return 0; }
 static inline void ftrace_startup_all(int command) { }
 
-# define ftrace_startup_sysctl()	do { } while (0)
-# define ftrace_shutdown_sysctl()	do { } while (0)
-
 static void ftrace_update_trampoline(struct ftrace_ops *ops)
 {
 }
@@ -7910,6 +7873,40 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
 EXPORT_SYMBOL_GPL(unregister_ftrace_function);
 
 #ifdef CONFIG_SYSCTL
+static void ftrace_startup_sysctl(void)
+{
+	int command;
+
+	if (unlikely(ftrace_disabled))
+		return;
+
+	/* Force update next time */
+	saved_ftrace_func = NULL;
+	/* ftrace_start_up is true if we want ftrace running */
+	if (ftrace_start_up) {
+		command = FTRACE_UPDATE_CALLS;
+		if (ftrace_graph_active)
+			command |= FTRACE_START_FUNC_RET;
+		ftrace_startup_enable(command);
+	}
+}
+
+static void ftrace_shutdown_sysctl(void)
+{
+	int command;
+
+	if (unlikely(ftrace_disabled))
+		return;
+
+	/* ftrace_start_up is true if ftrace is running */
+	if (ftrace_start_up) {
+		command = FTRACE_DISABLE_CALLS;
+		if (ftrace_graph_active)
+			command |= FTRACE_STOP_FUNC_RET;
+		ftrace_run_update_code(command);
+	}
+}
+
 static bool is_permanent_ops_registered(void)
 {
 	struct ftrace_ops *op;
-- 
2.30.2