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

1 files changed, 11 insertions, 11 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 33c897bb88c6..cc7cba20382e 100644
--- 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);
 }