kernel/time: move timer sysctls to its own file

kernel/sysctl.c is a kitchen sink where everyone leaves their dirty
dishes, this makes it very difficult to maintain.

To help with this maintenance let's start by moving sysctls to places
where they actually belong.  The proc sysctl maintainers do not want to
know what sysctl knobs you wish to add for your own piece of code, we
just care about the core logic.

So move the timer_migration sysctls to its own file.

Signed-off-by: tangmeng <tangmeng@uniontech.com>

include/linux/timer.h

@@ -198,10 +198,6 @@ extern enum hrtimer_restart it_real_fn(struct hrtimer *);
 
 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
 struct ctl_table;
-
-extern unsigned int sysctl_timer_migration;
-int timer_migration_handler(struct ctl_table *table, int write,
-			    void *buffer, size_t *lenp, loff_t *ppos);
 #endif
 
 unsigned long __round_jiffies(unsigned long j, int cpu);

kernel/sysctl.c

@@ -2656,17 +2656,6 @@ static struct ctl_table kern_table[] = {
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_ONE,
 	},
-#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
-	{
-		.procname	= "timer_migration",
-		.data		= &sysctl_timer_migration,
-		.maxlen		= sizeof(unsigned int),
-		.mode		= 0644,
-		.proc_handler	= timer_migration_handler,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
-	},
-#endif
 #ifdef CONFIG_BPF_SYSCALL
 	{
 		.procname	= "unprivileged_bpf_disabled",

kernel/time/timer.c

@@ -44,6 +44,7 @@
 #include <linux/slab.h>
 #include <linux/compat.h>
 #include <linux/random.h>
+#include <linux/sysctl.h>
 
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
@@ -223,7 +224,7 @@ static void timer_update_keys(struct work_struct *work);
 static DECLARE_WORK(timer_update_work, timer_update_keys);
 
 #ifdef CONFIG_SMP
-unsigned int sysctl_timer_migration = 1;
+static unsigned int sysctl_timer_migration = 1;
 
 DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
 
@@ -251,7 +252,8 @@ void timers_update_nohz(void)
 	schedule_work(&timer_update_work);
 }
 
-int timer_migration_handler(struct ctl_table *table, int write,
+#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
+static int timer_migration_handler(struct ctl_table *table, int write,
 			    void *buffer, size_t *lenp, loff_t *ppos)
 {
 	int ret;
@@ -264,6 +266,26 @@ int timer_migration_handler(struct ctl_table *table, int write,
 	return ret;
 }
 
+static struct ctl_table timer_sysctl[] = {
+	{
+		.procname       = "timer_migration",
+		.data           = &sysctl_timer_migration,
+		.maxlen         = sizeof(unsigned int),
+		.mode           = 0644,
+		.proc_handler   = timer_migration_handler,
+		.extra1         = SYSCTL_ZERO,
+		.extra2         = SYSCTL_ONE,
+	},
+	{}
+};
+
+static int __init timer_sysctl_init(void)
+{
+	register_sysctl_init("kernel", timer_sysctl);
+	return 0;
+}
+__initcall(timer_sysctl_init);
+#endif
 static inline bool is_timers_nohz_active(void)
 {
 	return static_branch_unlikely(&timers_nohz_active);