tick/nohz: Remove duplicate between tick_nohz_switch_to_nohz() and tick_setup_sched_t...

The ts->sched_timer initialization work of tick_nohz_switch_to_nohz()
is almost the same as that of tick_setup_sched_timer(), so adjust the
latter to get it reused by tick_nohz_switch_to_nohz().

This also makes the low resolution mode sched_timer benefit from the tick
skew boot option.

Signed-off-by: Peng Liu <liupeng17@lenovo.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-2-frederic@kernel.org

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 1fd106af747d1d37d9bdf98f46084bf24668df85..95f1f351dcd9717bb6240d61006182c488183bb4 100644 (file)
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -747,7 +747,7 @@ static void hrtimer_switch_to_hres(void)
        base->hres_active = 1;
        hrtimer_resolution = HIGH_RES_NSEC;
 
-       tick_setup_sched_timer();
+       tick_setup_sched_timer(NOHZ_MODE_HIGHRES);
        /* "Retrigger" the interrupt to get things going */
        retrigger_next_event(NULL);
 }

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 417bb7f880ca06f62224dcde6ee5d900a5cf573c..d4901654148d1a17b2a416472bf8e566b56fa334 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1471,9 +1471,6 @@ static inline void tick_nohz_activate(struct tick_sched *ts, int mode)
  */
 static void tick_nohz_switch_to_nohz(void)
 {
-       struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
-       ktime_t next;
-
        if (!tick_nohz_enabled)
                return;
 
@@ -1482,16 +1479,9 @@ static void tick_nohz_switch_to_nohz(void)
 
        /*
         * Recycle the hrtimer in 'ts', so we can share the
-        * hrtimer_forward_now() function with the highres code.
+        * highres code.
         */
-       hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
-       /* Get the next period */
-       next = tick_init_jiffy_update();
-
-       hrtimer_set_expires(&ts->sched_timer, next);
-       hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
-       tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
-       tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
+       tick_setup_sched_timer(NOHZ_MODE_LOWRES);
 }
 
 static inline void tick_nohz_irq_enter(void)
@@ -1570,7 +1560,11 @@ static enum hrtimer_restart tick_nohz_highres_handler(struct hrtimer *timer)
 
        return HRTIMER_RESTART;
 }
+#else
+#define tick_nohz_highres_handler NULL
+#endif /* CONFIG_HIGH_RES_TIMERS */
 
+#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
 static int sched_skew_tick;
 
 static int __init skew_tick(char *str)
@@ -1583,15 +1577,17 @@ early_param("skew_tick", skew_tick);
 
 /**
  * tick_setup_sched_timer - setup the tick emulation timer
+ * @mode: tick_nohz_mode to setup for
  */
-void tick_setup_sched_timer(void)
+void tick_setup_sched_timer(int mode)
 {
        struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
-       ktime_t now = ktime_get();
 
        /* Emulate tick processing via per-CPU hrtimers: */
        hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
-       ts->sched_timer.function = tick_nohz_highres_handler;
+
+       if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
+               ts->sched_timer.function = tick_nohz_highres_handler;
 
        /* Get the next period (per-CPU) */
        hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
@@ -1604,13 +1600,14 @@ void tick_setup_sched_timer(void)
                hrtimer_add_expires_ns(&ts->sched_timer, offset);
        }
 
-       hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
-       hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD);
-       tick_nohz_activate(ts, NOHZ_MODE_HIGHRES);
+       hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
+       if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
+               hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD);
+       else
+               tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
+       tick_nohz_activate(ts, mode);
 }
-#endif /* HIGH_RES_TIMERS */
 
-#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
 void tick_cancel_sched_timer(int cpu)
 {
        struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
@@ -1632,7 +1629,7 @@ void tick_cancel_sched_timer(int cpu)
        ts->idle_calls = idle_calls;
        ts->idle_sleeps = idle_sleeps;
 }
-#endif
+#endif /* CONFIG_NO_HZ_COMMON || CONFIG_HIGH_RES_TIMERS */
 
 /*
  * Async notification about clocksource changes

diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index 5ed5a9d41d5a7a9489f954635b64a5bf04c0cf6e..35808bbb8a47875d9b785a56fddeaa7967a7b867 100644 (file)
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -102,7 +102,7 @@ struct tick_sched {
 
 extern struct tick_sched *tick_get_tick_sched(int cpu);
 
-extern void tick_setup_sched_timer(void);
+extern void tick_setup_sched_timer(int mode);
 #if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
 extern void tick_cancel_sched_timer(int cpu);
 #else