[PATCH v14 23/25] sched: move sched clock initialization and merge with generic clock

[Pavel Tatashin <pasha.tatashin@oracle.com>]

sched_clock_postinit() initializes a generic clock on systems where no
other clock is porvided. This function may be called only after
timekeeping_init().

Rename sched_clock_postinit to generic_clock_inti() and call it from
sched_clock_init(). Move the call for sched_clock_init() until after
time_init().

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
---
 include/linux/sched_clock.h |  5 ++---
 init/main.c                 |  4 ++--
 kernel/sched/clock.c        | 27 +++++++++++++++++----------
 kernel/sched/core.c         |  1 -
 kernel/time/sched_clock.c   |  2 +-
 5 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/include/linux/sched_clock.h b/include/linux/sched_clock.h
index 411b52e424e1..abe28d5cb3f4 100644
--- a/include/linux/sched_clock.h
+++ b/include/linux/sched_clock.h
@@ -9,17 +9,16 @@
 #define LINUX_SCHED_CLOCK
 
 #ifdef CONFIG_GENERIC_SCHED_CLOCK
-extern void sched_clock_postinit(void);
+extern void generic_sched_clock_init(void);
 
 extern void sched_clock_register(u64 (*read)(void), int bits,
 				 unsigned long rate);
 #else
-static inline void sched_clock_postinit(void) { }
+static inline void generic_sched_clock_init(void) { }
 
 static inline void sched_clock_register(u64 (*read)(void), int bits,
 					unsigned long rate)
 {
-	;
 }
 #endif
 
diff --git a/init/main.c b/init/main.c
index 3b4ada11ed52..162d931c9511 100644
--- a/init/main.c
+++ b/init/main.c
@@ -79,7 +79,7 @@
 #include <linux/pti.h>
 #include <linux/blkdev.h>
 #include <linux/elevator.h>
-#include <linux/sched_clock.h>
+#include <linux/sched/clock.h>
 #include <linux/sched/task.h>
 #include <linux/sched/task_stack.h>
 #include <linux/context_tracking.h>
@@ -642,7 +642,7 @@ asmlinkage __visible void __init start_kernel(void)
 	softirq_init();
 	timekeeping_init();
 	time_init();
-	sched_clock_postinit();
+	sched_clock_init();
 	printk_safe_init();
 	perf_event_init();
 	profile_init();
diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
index 10c83e73837a..0e9dbb2d9aea 100644
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -53,6 +53,7 @@
  *
  */
 #include "sched.h"
+#include <linux/sched_clock.h>
 
 /*
  * Scheduler clock - returns current time in nanosec units.
@@ -68,11 +69,6 @@ EXPORT_SYMBOL_GPL(sched_clock);
 
 __read_mostly int sched_clock_running;
 
-void sched_clock_init(void)
-{
-	sched_clock_running = 1;
-}
-
 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
 /*
  * We must start with !__sched_clock_stable because the unstable -> stable
@@ -199,6 +195,15 @@ void clear_sched_clock_stable(void)
 		__clear_sched_clock_stable();
 }
 
+static void __sched_clock_gtod_offset(void)
+{
+	__gtod_offset = (sched_clock() + __sched_clock_offset) - ktime_get_ns();
+}
+
+void __init sched_clock_init(void)
+{
+	sched_clock_running = 1;
+}
 /*
  * We run this as late_initcall() such that it runs after all built-in drivers,
  * notably: acpi_processor and intel_idle, which can mark the TSC as unstable.
@@ -385,8 +390,6 @@ void sched_clock_tick(void)
 
 void sched_clock_tick_stable(void)
 {
-	u64 gtod, clock;
-
 	if (!sched_clock_stable())
 		return;
 
@@ -398,9 +401,7 @@ void sched_clock_tick_stable(void)
 	 * TSC to be unstable, any computation will be computing crap.
 	 */
 	local_irq_disable();
-	gtod = ktime_get_ns();
-	clock = sched_clock();
-	__gtod_offset = (clock + __sched_clock_offset) - gtod;
+	__sched_clock_gtod_offset();
 	local_irq_enable();
 }
 
@@ -434,6 +435,12 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
 
 #else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
 
+void __init sched_clock_init(void)
+{
+	sched_clock_running = 1;
+	generic_sched_clock_init();
+}
+
 u64 sched_clock_cpu(int cpu)
 {
 	if (unlikely(!sched_clock_running))
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fe365c9a08e9..552406e9713b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5954,7 +5954,6 @@ void __init sched_init(void)
 	int i, j;
 	unsigned long alloc_size = 0, ptr;
 
-	sched_clock_init();
 	wait_bit_init();
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
index 2d8f05aad442..cbc72c2c1fca 100644
--- a/kernel/time/sched_clock.c
+++ b/kernel/time/sched_clock.c
@@ -237,7 +237,7 @@ sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
 	pr_debug("Registered %pF as sched_clock source\n", read);
 }
 
-void __init sched_clock_postinit(void)
+void __init generic_sched_clock_init(void)
 {
 	/*
 	 * If no sched_clock() function has been provided at that point,
-- 
2.18.0