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tick: Get rid of tick_period

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[ Upstream commit b996544916429946bf4934c1c01a306d1690972c ]

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
Stable-dep-of: e9523a0d8189 ("tick/common: Align tick period with the HZ tick.")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Thomas Gleixner 2020-11-17 14:19:49 +01:00 • committed by Greg Kroah-Hartman
parent 3df29117d8
commit 04be737176
4 changed files with 15 additions and 18 deletions
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2
kernel/time/tick-broadcast.c
View file

@ -331,7 +331,7 @@ static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
bc_local = tick_do_periodic_broadcast(); bc_local = tick_do_periodic_broadcast();
if (clockevent_state_oneshot(dev)) { 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); clockevents_program_event(dev, next, true);
} }

8
kernel/time/tick-common.c
View file

@ -30,7 +30,6 @@ DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
* Tick next event: keeps track of the tick time * Tick next event: keeps track of the tick time
*/ */
ktime_t tick_next_period; ktime_t tick_next_period;
ktime_t tick_period;
/* /*
* tick_do_timer_cpu is a timer core internal variable which holds the CPU NR * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
@ -88,7 +87,7 @@ static void tick_periodic(int cpu)
write_seqcount_begin(&jiffies_seq); write_seqcount_begin(&jiffies_seq);
/* Keep track of the next tick event */ /* 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); do_timer(1);
write_seqcount_end(&jiffies_seq); write_seqcount_end(&jiffies_seq);
@ -127,7 +126,7 @@ void tick_handle_periodic(struct clock_event_device *dev)
* Setup the next period for devices, which do not have * Setup the next period for devices, which do not have
* periodic mode: * periodic mode:
*/ */
next = ktime_add(next, tick_period); next = ktime_add_ns(next, TICK_NSEC);
if (!clockevents_program_event(dev, next, false)) if (!clockevents_program_event(dev, next, false))
return; return;
@ -173,7 +172,7 @@ void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
for (;;) { for (;;) {
if (!clockevents_program_event(dev, next, false)) if (!clockevents_program_event(dev, next, false))
return; return;
next = ktime_add(next, tick_period); next = ktime_add_ns(next, TICK_NSEC);
} }
} }
} }
@ -220,7 +219,6 @@ static void tick_setup_device(struct tick_device *td,
tick_do_timer_cpu = cpu; tick_do_timer_cpu = cpu;
tick_next_period = ktime_get(); tick_next_period = ktime_get();
tick_period = NSEC_PER_SEC / HZ;
#ifdef CONFIG_NO_HZ_FULL #ifdef CONFIG_NO_HZ_FULL
/* /*
* The boot CPU may be nohz_full, in which case set * The boot CPU may be nohz_full, in which case set

1
kernel/time/tick-internal.h
View file

@ -15,7 +15,6 @@
DECLARE_PER_CPU(struct tick_device, tick_cpu_device); DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
extern ktime_t tick_next_period; extern ktime_t tick_next_period;
extern ktime_t tick_period;
extern int tick_do_timer_cpu __read_mostly; extern int tick_do_timer_cpu __read_mostly;
extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast); extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast);

22
kernel/time/tick-sched.c
View file

@ -92,17 +92,17 @@ static void tick_do_update_jiffies64(ktime_t now)
write_seqcount_begin(&jiffies_seq); write_seqcount_begin(&jiffies_seq);
delta = ktime_sub(now, tick_next_period); delta = ktime_sub(now, tick_next_period);
if (unlikely(delta >= tick_period)) { if (unlikely(delta >= TICK_NSEC)) {
/* Slow path for long idle sleep times */ /* Slow path for long idle sleep times */
s64 incr = ktime_to_ns(tick_period); s64 incr = TICK_NSEC;
ticks += ktime_divns(delta, incr); ticks += ktime_divns(delta, incr);
last_jiffies_update = ktime_add_ns(last_jiffies_update, last_jiffies_update = ktime_add_ns(last_jiffies_update,
incr * ticks); incr * ticks);
} else { } else {
last_jiffies_update = ktime_add(last_jiffies_update, last_jiffies_update = ktime_add_ns(last_jiffies_update,
tick_period); TICK_NSEC);
} }
do_timer(ticks); do_timer(ticks);
@ -112,7 +112,7 @@ static void tick_do_update_jiffies64(ktime_t now)
* pairs with the READ_ONCE() in the lockless quick check above. * pairs with the READ_ONCE() in the lockless quick check above.
*/ */
WRITE_ONCE(tick_next_period, WRITE_ONCE(tick_next_period,
ktime_add(last_jiffies_update, tick_period)); ktime_add_ns(last_jiffies_update, TICK_NSEC));
write_seqcount_end(&jiffies_seq); write_seqcount_end(&jiffies_seq);
raw_spin_unlock(&jiffies_lock); raw_spin_unlock(&jiffies_lock);
@ -659,7 +659,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
hrtimer_set_expires(&ts->sched_timer, ts->last_tick); hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
/* Forward the time to expire in the future */ /* 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) { if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
hrtimer_start_expires(&ts->sched_timer, hrtimer_start_expires(&ts->sched_timer,
@ -1221,7 +1221,7 @@ static void tick_nohz_handler(struct clock_event_device *dev)
if (unlikely(ts->tick_stopped)) if (unlikely(ts->tick_stopped))
return; 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); tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
} }
@ -1258,7 +1258,7 @@ static void tick_nohz_switch_to_nohz(void)
next = tick_init_jiffy_update(); next = tick_init_jiffy_update();
hrtimer_set_expires(&ts->sched_timer, next); 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_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
tick_nohz_activate(ts, NOHZ_MODE_LOWRES); tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
} }
@ -1324,7 +1324,7 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
if (unlikely(ts->tick_stopped)) if (unlikely(ts->tick_stopped))
return HRTIMER_NORESTART; return HRTIMER_NORESTART;
hrtimer_forward(timer, now, tick_period); hrtimer_forward(timer, now, TICK_NSEC);
return HRTIMER_RESTART; return HRTIMER_RESTART;
} }
@ -1358,13 +1358,13 @@ void tick_setup_sched_timer(void)
/* Offset the tick to avert jiffies_lock contention. */ /* Offset the tick to avert jiffies_lock contention. */
if (sched_skew_tick) { if (sched_skew_tick) {
u64 offset = ktime_to_ns(tick_period) >> 1; u64 offset = TICK_NSEC >> 1;
do_div(offset, num_possible_cpus()); do_div(offset, num_possible_cpus());
offset *= smp_processor_id(); offset *= smp_processor_id();
hrtimer_add_expires_ns(&ts->sched_timer, offset); 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); hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD);
tick_nohz_activate(ts, NOHZ_MODE_HIGHRES); tick_nohz_activate(ts, NOHZ_MODE_HIGHRES);
} }