rcu: Move rcu_stall related sysctls into rcu/tree_stall.h

Move sysctl_panic_on_rcu_stall and sysctl_max_rcu_stall_to_panic into
the kernel/rcu subdirectory. Make these static in tree_stall.h and
removed them as extern from panic.h as their scope is now confined into
one file.

This is part of a greater effort to move ctl tables into their
respective subsystems which will reduce the merge conflicts in
kernel/sysctl.c.

Reviewed-by: Luis Chamberlain <[email protected]>
Reviewed-by: Joel Fernandes <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Signed-off-by: Joel Granados <[email protected]>

Author: Joelgranados

include/linux/panic.h

@@ -25,8 +25,6 @@ extern int panic_on_warn;
 extern unsigned long panic_on_taint;
 extern bool panic_on_taint_nousertaint;
 
-extern int sysctl_panic_on_rcu_stall;
-extern int sysctl_max_rcu_stall_to_panic;
 extern int sysctl_panic_on_stackoverflow;
 
 extern bool crash_kexec_post_notifiers;

kernel/rcu/tree_stall.h

@@ -17,8 +17,37 @@
 // Controlling CPU stall warnings, including delay calculation.
 
 /* panic() on RCU Stall sysctl. */
-int sysctl_panic_on_rcu_stall __read_mostly;
-int sysctl_max_rcu_stall_to_panic __read_mostly;
+static int sysctl_panic_on_rcu_stall __read_mostly;
+static int sysctl_max_rcu_stall_to_panic __read_mostly;
+
+static const struct ctl_table rcu_stall_sysctl_table[] = {
+	{
+		.procname	= "panic_on_rcu_stall",
+		.data		= &sysctl_panic_on_rcu_stall,
+		.maxlen		= sizeof(sysctl_panic_on_rcu_stall),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{
+		.procname	= "max_rcu_stall_to_panic",
+		.data		= &sysctl_max_rcu_stall_to_panic,
+		.maxlen		= sizeof(sysctl_max_rcu_stall_to_panic),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ONE,
+		.extra2		= SYSCTL_INT_MAX,
+	},
+};
+
+static int __init init_rcu_stall_sysctl(void)
+{
+	register_sysctl_init("kernel", rcu_stall_sysctl_table);
+	return 0;
+}
+
+subsys_initcall(init_rcu_stall_sysctl);
 
 #ifdef CONFIG_SYSFS
 

kernel/sysctl.c

@@ -1706,26 +1706,6 @@ static const struct ctl_table kern_table[] = {
 		.proc_handler	= proc_dointvec,
 	},
 #endif
-#ifdef CONFIG_TREE_RCU
-	{
-		.procname	= "panic_on_rcu_stall",
-		.data		= &sysctl_panic_on_rcu_stall,
-		.maxlen		= sizeof(sysctl_panic_on_rcu_stall),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
-	},
-	{
-		.procname	= "max_rcu_stall_to_panic",
-		.data		= &sysctl_max_rcu_stall_to_panic,
-		.maxlen		= sizeof(sysctl_max_rcu_stall_to_panic),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ONE,
-		.extra2		= SYSCTL_INT_MAX,
-	},
-#endif
 };
 
 int __init sysctl_init_bases(void)