diff options
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/tick-internal.h | 3 | ||||
| -rw-r--r-- | kernel/time/tick-sched.c | 25 | ||||
| -rw-r--r-- | kernel/time/timer.c | 110 |
3 files changed, 79 insertions, 59 deletions
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index 649f2b48e8..481b7ab65e 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -56,7 +56,6 @@ extern int clockevents_program_event(struct clock_event_device *dev, ktime_t expires, bool force); extern void clockevents_handle_noop(struct clock_event_device *dev); extern int __clockevents_update_freq(struct clock_event_device *dev, u32 freq); -extern ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt); /* Broadcasting support */ # ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST @@ -197,3 +196,5 @@ void hrtimers_resume_local(void); #else #define JIFFIES_SHIFT 8 #endif + +extern ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt); diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index ca2d59579f..01fb50c1b1 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -839,6 +839,10 @@ static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu) ts->next_timer = next_tick; } + /* Make sure next_tick is never before basemono! */ + if (WARN_ON_ONCE(basemono > next_tick)) + next_tick = basemono; + /* * If the tick is due in the next period, keep it ticking or * force prod the timer. @@ -887,7 +891,6 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu) struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); u64 basemono = ts->timer_expires_base; u64 expires = ts->timer_expires; - ktime_t tick = expires; /* Make sure we won't be trying to stop it twice in a row. */ ts->timer_expires_base = 0; @@ -910,7 +913,7 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu) /* Skip reprogram of event if it's not changed */ if (ts->tick_stopped && (expires == ts->next_tick)) { /* Sanity check: make sure clockevent is actually programmed */ - if (tick == KTIME_MAX || ts->next_tick == hrtimer_get_expires(&ts->sched_timer)) + if (expires == KTIME_MAX || ts->next_tick == hrtimer_get_expires(&ts->sched_timer)) return; WARN_ON_ONCE(1); @@ -920,11 +923,11 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu) } /* - * nohz_stop_sched_tick() can be called several times before - * nohz_restart_sched_tick() is called. This happens when - * interrupts arrive which do not cause a reschedule. In the - * first call we save the current tick time, so we can restart - * the scheduler tick in nohz_restart_sched_tick(). + * tick_nohz_stop_tick() can be called several times before + * tick_nohz_restart_sched_tick() is called. This happens when + * interrupts arrive which do not cause a reschedule. In the first + * call we save the current tick time, so we can restart the + * scheduler tick in tick_nohz_restart_sched_tick(). */ if (!ts->tick_stopped) { calc_load_nohz_start(); @@ -935,7 +938,7 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu) trace_tick_stop(1, TICK_DEP_MASK_NONE); } - ts->next_tick = tick; + ts->next_tick = expires; /* * If the expiration time == KTIME_MAX, then we simply stop @@ -950,11 +953,11 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu) } if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { - hrtimer_start(&ts->sched_timer, tick, + hrtimer_start(&ts->sched_timer, expires, HRTIMER_MODE_ABS_PINNED_HARD); } else { - hrtimer_set_expires(&ts->sched_timer, tick); - tick_program_event(tick, 1); + hrtimer_set_expires(&ts->sched_timer, expires); + tick_program_event(expires, 1); } } diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 63a8ce7177..352b161113 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -571,18 +571,15 @@ static int calc_wheel_index(unsigned long expires, unsigned long clk, static void trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer) { - if (!is_timers_nohz_active()) - return; - /* - * TODO: This wants some optimizing similar to the code below, but we - * will do that when we switch from push to pull for deferrable timers. + * Deferrable timers do not prevent the CPU from entering dynticks and + * are not taken into account on the idle/nohz_full path. An IPI when a + * new deferrable timer is enqueued will wake up the remote CPU but + * nothing will be done with the deferrable timer base. Therefore skip + * the remote IPI for deferrable timers completely. */ - if (timer->flags & TIMER_DEFERRABLE) { - if (tick_nohz_full_cpu(base->cpu)) - wake_up_nohz_cpu(base->cpu); + if (!is_timers_nohz_active() || timer->flags & TIMER_DEFERRABLE) return; - } /* * We might have to IPI the remote CPU if the base is idle and the @@ -606,7 +603,7 @@ static void enqueue_timer(struct timer_base *base, struct timer_list *timer, __set_bit(idx, base->pending_map); timer_set_idx(timer, idx); - trace_timer_start(timer, timer->expires, timer->flags); + trace_timer_start(timer, bucket_expiry); /* * Check whether this is the new first expiring timer. The @@ -942,31 +939,34 @@ get_target_base(struct timer_base *base, unsigned tflags) return get_timer_this_cpu_base(tflags); } -static inline void forward_timer_base(struct timer_base *base) +static inline void __forward_timer_base(struct timer_base *base, + unsigned long basej) { - unsigned long jnow = READ_ONCE(jiffies); - /* - * No need to forward if we are close enough below jiffies. - * Also while executing timers, base->clk is 1 offset ahead - * of jiffies to avoid endless requeuing to current jiffies. + * Check whether we can forward the base. We can only do that when + * @basej is past base->clk otherwise we might rewind base->clk. */ - if ((long)(jnow - base->clk) < 1) + if (time_before_eq(basej, base->clk)) return; /* * If the next expiry value is > jiffies, then we fast forward to * jiffies otherwise we forward to the next expiry value. */ - if (time_after(base->next_expiry, jnow)) { - base->clk = jnow; + if (time_after(base->next_expiry, basej)) { + base->clk = basej; } else { if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk))) return; base->clk = base->next_expiry; } + } +static inline void forward_timer_base(struct timer_base *base) +{ + __forward_timer_base(base, READ_ONCE(jiffies)); +} /* * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means @@ -1803,8 +1803,10 @@ static int next_pending_bucket(struct timer_base *base, unsigned offset, /* * Search the first expiring timer in the various clock levels. Caller must * hold base->lock. + * + * Store next expiry time in base->next_expiry. */ -static unsigned long __next_timer_interrupt(struct timer_base *base) +static void next_expiry_recalc(struct timer_base *base) { unsigned long clk, next, adj; unsigned lvl, offset = 0; @@ -1870,10 +1872,9 @@ static unsigned long __next_timer_interrupt(struct timer_base *base) clk += adj; } + base->next_expiry = next; base->next_expiry_recalc = false; base->timers_pending = !(next == base->clk + NEXT_TIMER_MAX_DELTA); - - return next; } #ifdef CONFIG_NO_HZ_COMMON @@ -1921,8 +1922,9 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expires) u64 get_next_timer_interrupt(unsigned long basej, u64 basem) { struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]); + unsigned long nextevt = basej + NEXT_TIMER_MAX_DELTA; u64 expires = KTIME_MAX; - unsigned long nextevt; + bool was_idle; /* * Pretend that there is no timer pending if the cpu is offline. @@ -1933,37 +1935,44 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) raw_spin_lock(&base->lock); if (base->next_expiry_recalc) - base->next_expiry = __next_timer_interrupt(base); - nextevt = base->next_expiry; + next_expiry_recalc(base); /* * We have a fresh next event. Check whether we can forward the - * base. We can only do that when @basej is past base->clk - * otherwise we might rewind base->clk. + * base. */ - if (time_after(basej, base->clk)) { - if (time_after(nextevt, basej)) - base->clk = basej; - else if (time_after(nextevt, base->clk)) - base->clk = nextevt; - } + __forward_timer_base(base, basej); - if (time_before_eq(nextevt, basej)) { - expires = basem; - base->is_idle = false; + if (base->timers_pending) { + nextevt = base->next_expiry; + + /* If we missed a tick already, force 0 delta */ + if (time_before(nextevt, basej)) + nextevt = basej; + expires = basem + (u64)(nextevt - basej) * TICK_NSEC; } else { - if (base->timers_pending) - expires = basem + (u64)(nextevt - basej) * TICK_NSEC; /* - * If we expect to sleep more than a tick, mark the base idle. - * Also the tick is stopped so any added timer must forward - * the base clk itself to keep granularity small. This idle - * logic is only maintained for the BASE_STD base, deferrable - * timers may still see large granularity skew (by design). + * Move next_expiry for the empty base into the future to + * prevent a unnecessary raise of the timer softirq when the + * next_expiry value will be reached even if there is no timer + * pending. */ - if ((expires - basem) > TICK_NSEC) - base->is_idle = true; + base->next_expiry = nextevt; } + + /* + * Base is idle if the next event is more than a tick away. + * + * If the base is marked idle then any timer add operation must forward + * the base clk itself to keep granularity small. This idle logic is + * only maintained for the BASE_STD base, deferrable timers may still + * see large granularity skew (by design). + */ + was_idle = base->is_idle; + base->is_idle = time_after(nextevt, basej + 1); + if (was_idle != base->is_idle) + trace_timer_base_idle(base->is_idle, base->cpu); + raw_spin_unlock(&base->lock); return cmp_next_hrtimer_event(basem, expires); @@ -1984,7 +1993,10 @@ void timer_clear_idle(void) * sending the IPI a few instructions smaller for the cost of taking * the lock in the exit from idle path. */ - base->is_idle = false; + if (base->is_idle) { + base->is_idle = false; + trace_timer_base_idle(false, smp_processor_id()); + } } #endif @@ -2015,8 +2027,12 @@ static inline void __run_timers(struct timer_base *base) */ WARN_ON_ONCE(!levels && !base->next_expiry_recalc && base->timers_pending); + /* + * While executing timers, base->clk is set 1 offset ahead of + * jiffies to avoid endless requeuing to current jiffies. + */ base->clk++; - base->next_expiry = __next_timer_interrupt(base); + next_expiry_recalc(base); while (levels--) expire_timers(base, heads + levels); |