tick: Split nohz and highres features from nohz_mode

The nohz mode field tells about low resolution nohz mode or high
resolution nohz mode but it doesn't tell about high resolution non-nohz
mode.

In order to retrieve the latter state, tick_cancel_sched_timer() must
fiddle with struct hrtimer's internals to guess if the tick has been
initialized in high resolution.

Move instead the nohz mode field information into the tick flags and
provide two new bits: one to know if the tick is in nohz mode and
another one to know if the tick is in high resolution. The combination
of those two flags provides all the needed informations to determine
which of the three tick modes is running.

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/20240225225508.11587-14-frederic@kernel.org

1 files changed, 17 insertions, 15 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 4aa7ce04a72c..dcb9f0394182 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -831,7 +831,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
 	/* Forward the time to expire in the future */
 	hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
 
-	if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
+	if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES)) {
 		hrtimer_start_expires(&ts->sched_timer,
 				      HRTIMER_MODE_ABS_PINNED_HARD);
 	} else {
@@ -1040,14 +1040,14 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
 	 * the tick timer.
 	 */
 	if (unlikely(expires == KTIME_MAX)) {
-		if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
+		if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES))
 			hrtimer_cancel(&ts->sched_timer);
 		else
 			tick_program_event(KTIME_MAX, 1);
 		return;
 	}
 
-	if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
+	if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES)) {
 		hrtimer_start(&ts->sched_timer, expires,
 			      HRTIMER_MODE_ABS_PINNED_HARD);
 	} else {
@@ -1108,7 +1108,7 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts)
 	if (!tick_nohz_full_cpu(smp_processor_id()))
 		return;
 
-	if (ts->nohz_mode == NOHZ_MODE_INACTIVE)
+	if (!tick_sched_flag_test(ts, TS_FLAG_NOHZ))
 		return;
 
 	__tick_nohz_full_update_tick(ts, ktime_get());
@@ -1168,7 +1168,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
 		return false;
 	}
 
-	if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
+	if (unlikely(!tick_sched_flag_test(ts, TS_FLAG_NOHZ)))
 		return false;
 
 	if (need_resched())
@@ -1487,11 +1487,11 @@ static void tick_nohz_lowres_handler(struct clock_event_device *dev)
 		tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
 }
 
-static inline void tick_nohz_activate(struct tick_sched *ts, int mode)
+static inline void tick_nohz_activate(struct tick_sched *ts)
 {
 	if (!tick_nohz_enabled)
 		return;
-	ts->nohz_mode = mode;
+	tick_sched_flag_set(ts, TS_FLAG_NOHZ);
 	/* One update is enough */
 	if (!test_and_set_bit(0, &tick_nohz_active))
 		timers_update_nohz();
@@ -1512,7 +1512,7 @@ static void tick_nohz_switch_to_nohz(void)
 	 * Recycle the hrtimer in 'ts', so we can share the
 	 * highres code.
 	 */
-	tick_setup_sched_timer(NOHZ_MODE_LOWRES);
+	tick_setup_sched_timer(false);
 }
 
 static inline void tick_nohz_irq_enter(void)
@@ -1540,7 +1540,7 @@ static inline void tick_nohz_irq_enter(void)
 
 static inline void tick_nohz_switch_to_nohz(void) { }
 static inline void tick_nohz_irq_enter(void) { }
-static inline void tick_nohz_activate(struct tick_sched *ts, int mode) { }
+static inline void tick_nohz_activate(struct tick_sched *ts) { }
 
 #endif /* CONFIG_NO_HZ_COMMON */
 
@@ -1567,15 +1567,17 @@ 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(int mode)
+void tick_setup_sched_timer(bool hrtimer)
 {
 	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
 
 	/* Emulate tick processing via per-CPU hrtimers: */
 	hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
 
-	if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
+	if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && hrtimer) {
+		tick_sched_flag_set(ts, TS_FLAG_HIGHRES);
 		ts->sched_timer.function = tick_nohz_handler;
+	}
 
 	/* Get the next period (per-CPU) */
 	hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
@@ -1589,11 +1591,11 @@ void tick_setup_sched_timer(int mode)
 	}
 
 	hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
-	if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
+	if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && hrtimer)
 		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);
+	tick_nohz_activate(ts);
 }
 
 void tick_cancel_sched_timer(int cpu)
@@ -1602,7 +1604,7 @@ void tick_cancel_sched_timer(int cpu)
 	ktime_t idle_sleeptime, iowait_sleeptime;
 	unsigned long idle_calls, idle_sleeps;
 
-	if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && ts->sched_timer.base)
+	if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES))
 		hrtimer_cancel(&ts->sched_timer);
 
 	idle_sleeptime = ts->idle_sleeptime;
@@ -1652,7 +1654,7 @@ int tick_check_oneshot_change(int allow_nohz)
 	if (!test_and_clear_bit(0, &ts->check_clocks))
 		return 0;
 
-	if (ts->nohz_mode != NOHZ_MODE_INACTIVE)
+	if (tick_sched_flag_test(ts, TS_FLAG_NOHZ))
 		return 0;
 
 	if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())