tick: Get rid of tick_period

The variable tick_period is initialized to NSEC_PER_TICK / HZ during boot
and never updated again.

If NSEC_PER_TICK is not an integer multiple of HZ this computation is less
accurate than TICK_NSEC which has proper rounding in place.

Aside of the inaccuracy there is no reason for having this variable at
all. It's just a pointless indirection and all usage sites can just use the
TICK_NSEC constant.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.766643526@linutronix.de

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 2a47c8f80e53bfbb024643c8cd01e1cf4ab96fe2..5a23829372c7fc2d4b60814b397a1af9e72298ba 100644 (file)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -331,7 +331,7 @@ static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
        bc_local = tick_do_periodic_broadcast();
 
        if (clockevent_state_oneshot(dev)) {
-               ktime_t next = ktime_add(dev->next_event, tick_period);
+               ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);
 
                clockevents_program_event(dev, next, true);
        }

diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 68504eb0d38babfbff5f5ec12a5fcc292ae241a9..a03764df5366e97e746d595a2badb0e19c4722f9 100644 (file)
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -32,7 +32,6 @@ DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
  * no requirement to write hold the jiffies seqcount for it.
  */
 ktime_t tick_next_period;
-ktime_t tick_period;
 
 /*
  * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
@@ -90,7 +89,7 @@ static void tick_periodic(int cpu)
                write_seqcount_begin(&jiffies_seq);
 
                /* Keep track of the next tick event */
-               tick_next_period = ktime_add(tick_next_period, tick_period);
+               tick_next_period = ktime_add_ns(tick_next_period, TICK_NSEC);
 
                do_timer(1);
                write_seqcount_end(&jiffies_seq);
@@ -129,7 +128,7 @@ void tick_handle_periodic(struct clock_event_device *dev)
                 * Setup the next period for devices, which do not have
                 * periodic mode:
                 */
-               next = ktime_add(next, tick_period);
+               next = ktime_add_ns(next, TICK_NSEC);
 
                if (!clockevents_program_event(dev, next, false))
                        return;
@@ -175,7 +174,7 @@ void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
                for (;;) {
                        if (!clockevents_program_event(dev, next, false))
                                return;
-                       next = ktime_add(next, tick_period);
+                       next = ktime_add_ns(next, TICK_NSEC);
                }
        }
 }
@@ -222,7 +221,6 @@ static void tick_setup_device(struct tick_device *td,
                        tick_do_timer_cpu = cpu;
 
                        tick_next_period = ktime_get();
-                       tick_period = NSEC_PER_SEC / HZ;
 #ifdef CONFIG_NO_HZ_FULL
                        /*
                         * The boot CPU may be nohz_full, in which case set

diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 7b249613672922757b69ad8992a6c56029942f7e..7a981c9e87a4aafa8dcbca51d26f541d44bf969b 100644 (file)
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -15,7 +15,6 @@
 
 DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
 extern ktime_t tick_next_period;
-extern ktime_t tick_period;
 extern int tick_do_timer_cpu __read_mostly;
 
 extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast);

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 33c897bb88c6ef419b08bf18f9e7507760451dbb..cc7cba20382ec0b84a27d898134b51d406b42bab 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -95,17 +95,17 @@ static void tick_do_update_jiffies64(ktime_t now)
        write_seqcount_begin(&jiffies_seq);
 
        delta = ktime_sub(now, tick_next_period);
-       if (unlikely(delta >= tick_period)) {
+       if (unlikely(delta >= TICK_NSEC)) {
                /* Slow path for long idle sleep times */
-               s64 incr = ktime_to_ns(tick_period);
+               s64 incr = TICK_NSEC;
 
                ticks += ktime_divns(delta, incr);
 
                last_jiffies_update = ktime_add_ns(last_jiffies_update,
                                                   incr * ticks);
        } else {
-               last_jiffies_update = ktime_add(last_jiffies_update,
-                                               tick_period);
+               last_jiffies_update = ktime_add_ns(last_jiffies_update,
+                                                  TICK_NSEC);
        }
 
        /* Advance jiffies to complete the jiffies_seq protected job */
@@ -116,7 +116,7 @@ static void tick_do_update_jiffies64(ktime_t now)
         * pairs with the READ_ONCE() in the lockless quick check above.
         */
        WRITE_ONCE(tick_next_period,
-                  ktime_add(last_jiffies_update, tick_period));
+                  ktime_add_ns(last_jiffies_update, TICK_NSEC));
 
        /*
         * Release the sequence count. calc_global_load() below is not
@@ -691,7 +691,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
        hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
 
        /* Forward the time to expire in the future */
-       hrtimer_forward(&ts->sched_timer, now, tick_period);
+       hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
 
        if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
                hrtimer_start_expires(&ts->sched_timer,
@@ -1260,7 +1260,7 @@ static void tick_nohz_handler(struct clock_event_device *dev)
        if (unlikely(ts->tick_stopped))
                return;
 
-       hrtimer_forward(&ts->sched_timer, now, tick_period);
+       hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
        tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
 }
 
@@ -1297,7 +1297,7 @@ static void tick_nohz_switch_to_nohz(void)
        next = tick_init_jiffy_update();
 
        hrtimer_set_expires(&ts->sched_timer, next);
-       hrtimer_forward_now(&ts->sched_timer, tick_period);
+       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);
 }
@@ -1363,7 +1363,7 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
        if (unlikely(ts->tick_stopped))
                return HRTIMER_NORESTART;
 
-       hrtimer_forward(timer, now, tick_period);
+       hrtimer_forward(timer, now, TICK_NSEC);
 
        return HRTIMER_RESTART;
 }
@@ -1397,13 +1397,13 @@ void tick_setup_sched_timer(void)
 
        /* Offset the tick to avert jiffies_lock contention. */
        if (sched_skew_tick) {
-               u64 offset = ktime_to_ns(tick_period) >> 1;
+               u64 offset = TICK_NSEC >> 1;
                do_div(offset, num_possible_cpus());
                offset *= smp_processor_id();
                hrtimer_add_expires_ns(&ts->sched_timer, offset);
        }
 
-       hrtimer_forward(&ts->sched_timer, now, tick_period);
+       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);
 }