From: Thomas Gleixner tglx@linutronix.de
[ 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 --- kernel/time/tick-broadcast.c | 2 +- kernel/time/tick-common.c | 8 +++----- kernel/time/tick-internal.h | 1 - kernel/time/tick-sched.c | 22 +++++++++++----------- 4 files changed, 15 insertions(+), 18 deletions(-)
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index e51778c312f1c..ce7339ff10d22 100644 --- 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 6c9c342dd0e53..92bf99d558b48 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -30,7 +30,6 @@ DEFINE_PER_CPU(struct tick_device, tick_cpu_device); * Tick next event: keeps track of the tick time */ ktime_t tick_next_period; -ktime_t tick_period;
/* * 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);
/* 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); @@ -127,7 +126,7 @@ 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; @@ -173,7 +172,7 @@ 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); } } } @@ -220,7 +219,6 @@ 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 5294f5b1f9550..e61c1244e7d46 100644 --- 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 3b00167656d78..1b5037ba4ec40 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -92,17 +92,17 @@ 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); }
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. */ 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); 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);
/* 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, @@ -1221,7 +1221,7 @@ 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); }
@@ -1258,7 +1258,7 @@ 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); } @@ -1324,7 +1324,7 @@ 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; } @@ -1358,13 +1358,13 @@ 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); }