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

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 3e95474199ac16ee545015bd5fb55e66fd821294..70625dff62ce10150a49110715e5edf49ff19147 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(NOHZ_MODE_HIGHRES);
+       tick_setup_sched_timer(true);
        /* "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 4aa7ce04a72cc14b126a07292a27140faacf1293..dcb9f0394182b34a723c4e964fbc5af0ceae108e 100644 (file)
--- 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())

diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index 07a4c0144c47fff4cad5b6fd35518426fdc27c51..bbe72a078985416ead473169c6fac3c1b155a0e6 100644 (file)
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -14,12 +14,6 @@ struct tick_device {
        enum tick_device_mode mode;
 };
 
-enum tick_nohz_mode {
-       NOHZ_MODE_INACTIVE,
-       NOHZ_MODE_LOWRES,
-       NOHZ_MODE_HIGHRES,
-};
-
 /* The CPU is in the tick idle mode */
 #define TS_FLAG_INIDLE         BIT(0)
 /* The idle tick has been stopped */
@@ -31,6 +25,10 @@ enum tick_nohz_mode {
 #define TS_FLAG_IDLE_ACTIVE    BIT(2)
 /* CPU was the last one doing do_timer before going idle */
 #define TS_FLAG_DO_TIMER_LAST  BIT(3)
+/* NO_HZ is enabled */
+#define TS_FLAG_NOHZ           BIT(4)
+/* High resolution tick mode */
+#define TS_FLAG_HIGHRES                BIT(5)
 
 /**
  * struct tick_sched - sched tick emulation and no idle tick control/stats
@@ -84,7 +82,6 @@ struct tick_sched {
        ktime_t                         idle_entrytime;
 
        /* Tick stop */
-       enum tick_nohz_mode             nohz_mode;
        unsigned long                   last_jiffies;
        u64                             timer_expires_base;
        u64                             timer_expires;
@@ -107,7 +104,7 @@ struct tick_sched {
 
 extern struct tick_sched *tick_get_tick_sched(int cpu);
 
-extern void tick_setup_sched_timer(int mode);
+extern void tick_setup_sched_timer(bool hrtimer);
 #if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
 extern void tick_cancel_sched_timer(int cpu);
 #else

diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index 38f81d836fc51f4bb9c1959d55e8a73b5526181c..1c311c46da5074c1cb33027c96638e68a606574a 100644 (file)
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -152,7 +152,8 @@ static void print_cpu(struct seq_file *m, int cpu, u64 now)
 
        {
                struct tick_sched *ts = tick_get_tick_sched(cpu);
-               P(nohz_mode);
+               P_flag(nohz, TS_FLAG_NOHZ);
+               P_flag(highres, TS_FLAG_HIGHRES);
                P_ns(last_tick);
                P_flag(tick_stopped, TS_FLAG_STOPPED);
                P(idle_jiffies);
@@ -259,7 +260,7 @@ static void timer_list_show_tickdevices_header(struct seq_file *m)
 
 static inline void timer_list_header(struct seq_file *m, u64 now)
 {
-       SEQ_printf(m, "Timer List Version: v0.9\n");
+       SEQ_printf(m, "Timer List Version: v0.10\n");
        SEQ_printf(m, "HRTIMER_MAX_CLOCK_BASES: %d\n", HRTIMER_MAX_CLOCK_BASES);
        SEQ_printf(m, "now at %Ld nsecs\n", (unsigned long long)now);
        SEQ_printf(m, "\n");