diff options
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/Kconfig | 15 | ||||
| -rw-r--r-- | kernel/time/Makefile | 2 | ||||
| -rw-r--r-- | kernel/time/clocksource.c | 8 | ||||
| -rw-r--r-- | kernel/time/tick-broadcast.c | 191 | ||||
| -rw-r--r-- | kernel/time/tick-common.c | 26 | ||||
| -rw-r--r-- | kernel/time/tick-internal.h | 49 | ||||
| -rw-r--r-- | kernel/time/tick-oneshot.c | 84 | ||||
| -rw-r--r-- | kernel/time/tick-sched.c | 558 |
8 files changed, 930 insertions, 3 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig new file mode 100644 index 000000000000..9ec54eb3667f --- /dev/null +++ b/kernel/time/Kconfig @@ -0,0 +1,15 @@ +# +# Timer subsystem related configuration options +# +config TICK_ONESHOT + bool + default n + +config NO_HZ + bool "Tickless System (Dynamic Ticks)" + depends on GENERIC_TIME && GENERIC_CLOCKEVENTS + select TICK_ONESHOT + help + This option enables a tickless system: timer interrupts will + only trigger on an as-needed basis both when the system is + busy and when the system is idle. diff --git a/kernel/time/Makefile b/kernel/time/Makefile index a941743c3ff8..f246bc836b9a 100644 --- a/kernel/time/Makefile +++ b/kernel/time/Makefile @@ -3,3 +3,5 @@ obj-y += ntp.o clocksource.o jiffies.o obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o obj-$(CONFIG_GENERIC_CLOCKEVENTS) += tick-common.o obj-$(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) += tick-broadcast.o +obj-$(CONFIG_TICK_ONESHOT) += tick-oneshot.o +obj-$(CONFIG_TICK_ONESHOT) += tick-sched.o diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 3cb8ac978270..193a0793af95 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -29,6 +29,7 @@ #include <linux/init.h> #include <linux/module.h> #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ +#include <linux/tick.h> /* XXX - Would like a better way for initializing curr_clocksource */ extern struct clocksource clocksource_jiffies; @@ -109,6 +110,13 @@ static void clocksource_watchdog(unsigned long data) if ((cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) && (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) { cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; + /* + * We just marked the clocksource as + * highres-capable, notify the rest of the + * system as well so that we transition + * into high-res mode: + */ + tick_clock_notify(); } cs->flags |= CLOCK_SOURCE_WATCHDOG; cs->wd_last = csnow; diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index 0ee4968ff791..8314ecb32d33 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -29,7 +29,7 @@ struct tick_device tick_broadcast_device; static cpumask_t tick_broadcast_mask; -DEFINE_SPINLOCK(tick_broadcast_lock); +static DEFINE_SPINLOCK(tick_broadcast_lock); /* * Start the device in periodic mode @@ -215,6 +215,8 @@ static void tick_do_broadcast_on_off(void *why) else { if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) tick_broadcast_start_periodic(bc); + else + tick_broadcast_setup_oneshot(bc); } out: spin_unlock_irqrestore(&tick_broadcast_lock, flags); @@ -268,3 +270,190 @@ void tick_shutdown_broadcast(unsigned int *cpup) spin_unlock_irqrestore(&tick_broadcast_lock, flags); } + +#ifdef CONFIG_TICK_ONESHOT + +static cpumask_t tick_broadcast_oneshot_mask; + +static int tick_broadcast_set_event(ktime_t expires, int force) +{ + struct clock_event_device *bc = tick_broadcast_device.evtdev; + ktime_t now = ktime_get(); + int res; + + for(;;) { + res = clockevents_program_event(bc, expires, now); + if (!res || !force) + return res; + now = ktime_get(); + expires = ktime_add(now, ktime_set(0, bc->min_delta_ns)); + } +} + +/* + * Reprogram the broadcast device: + * + * Called with tick_broadcast_lock held and interrupts disabled. + */ +static int tick_broadcast_reprogram(void) +{ + ktime_t expires = { .tv64 = KTIME_MAX }; + struct tick_device *td; + int cpu; + + /* + * Find the event which expires next: + */ + for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS; + cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) { + td = &per_cpu(tick_cpu_device, cpu); + if (td->evtdev->next_event.tv64 < expires.tv64) + expires = td->evtdev->next_event; + } + + if (expires.tv64 == KTIME_MAX) + return 0; + + return tick_broadcast_set_event(expires, 0); +} + +/* + * Handle oneshot mode broadcasting + */ +static void tick_handle_oneshot_broadcast(struct clock_event_device *dev) +{ + struct tick_device *td; + cpumask_t mask; + ktime_t now; + int cpu; + + spin_lock(&tick_broadcast_lock); +again: + dev->next_event.tv64 = KTIME_MAX; + mask = CPU_MASK_NONE; + now = ktime_get(); + /* Find all expired events */ + for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS; + cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) { + td = &per_cpu(tick_cpu_device, cpu); + if (td->evtdev->next_event.tv64 <= now.tv64) + cpu_set(cpu, mask); + } + + /* + * Wakeup the cpus which have an expired event. The broadcast + * device is reprogrammed in the return from idle code. + */ + if (!tick_do_broadcast(mask)) { + /* + * The global event did not expire any CPU local + * events. This happens in dyntick mode, as the + * maximum PIT delta is quite small. + */ + if (tick_broadcast_reprogram()) + goto again; + } + spin_unlock(&tick_broadcast_lock); +} + +/* + * Powerstate information: The system enters/leaves a state, where + * affected devices might stop + */ +void tick_broadcast_oneshot_control(unsigned long reason) +{ + struct clock_event_device *bc, *dev; + struct tick_device *td; + unsigned long flags; + int cpu; + + spin_lock_irqsave(&tick_broadcast_lock, flags); + + /* + * Periodic mode does not care about the enter/exit of power + * states + */ + if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) + goto out; + + bc = tick_broadcast_device.evtdev; + cpu = smp_processor_id(); + td = &per_cpu(tick_cpu_device, cpu); + dev = td->evtdev; + + if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) + goto out; + + if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) { + if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) { + cpu_set(cpu, tick_broadcast_oneshot_mask); + clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN); + if (dev->next_event.tv64 < bc->next_event.tv64) + tick_broadcast_set_event(dev->next_event, 1); + } + } else { + if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) { + cpu_clear(cpu, tick_broadcast_oneshot_mask); + clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); + if (dev->next_event.tv64 != KTIME_MAX) + tick_program_event(dev->next_event, 1); + } + } + +out: + spin_unlock_irqrestore(&tick_broadcast_lock, flags); +} + +/** + * tick_broadcast_setup_highres - setup the broadcast device for highres + */ +void tick_broadcast_setup_oneshot(struct clock_event_device *bc) +{ + if (bc->mode != CLOCK_EVT_MODE_ONESHOT) { + bc->event_handler = tick_handle_oneshot_broadcast; + clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT); + bc->next_event.tv64 = KTIME_MAX; + } +} + +/* + * Select oneshot operating mode for the broadcast device + */ +void tick_broadcast_switch_to_oneshot(void) +{ + struct clock_event_device *bc; + unsigned long flags; + + spin_lock_irqsave(&tick_broadcast_lock, flags); + + tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT; + bc = tick_broadcast_device.evtdev; + if (bc) + tick_broadcast_setup_oneshot(bc); + spin_unlock_irqrestore(&tick_broadcast_lock, flags); +} + + +/* + * Remove a dead CPU from broadcasting + */ +void tick_shutdown_broadcast_oneshot(unsigned int *cpup) +{ + struct clock_event_device *bc; + unsigned long flags; + unsigned int cpu = *cpup; + + spin_lock_irqsave(&tick_broadcast_lock, flags); + + bc = tick_broadcast_device.evtdev; + cpu_clear(cpu, tick_broadcast_oneshot_mask); + + if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT) { + if (bc && cpus_empty(tick_broadcast_oneshot_mask)) + clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN); + } + + spin_unlock_irqrestore(&tick_broadcast_lock, flags); +} + +#endif diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index 48167a6ae55c..c35d449be031 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -34,6 +34,16 @@ ktime_t tick_period; static int tick_do_timer_cpu = -1; DEFINE_SPINLOCK(tick_device_lock); +/** + * tick_is_oneshot_available - check for a oneshot capable event device + */ +int tick_is_oneshot_available(void) +{ + struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; + + return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT); +} + /* * Periodic tick */ @@ -162,6 +172,8 @@ static void tick_setup_device(struct tick_device *td, if (td->mode == TICKDEV_MODE_PERIODIC) tick_setup_periodic(newdev, 0); + else + tick_setup_oneshot(newdev, handler, next_event); } /* @@ -209,6 +221,12 @@ static int tick_check_new_device(struct clock_event_device *newdev) */ if (curdev) { /* + * Prefer one shot capable devices ! + */ + if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) && + !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) + goto out_bc; + /* * Check the rating */ if (curdev->rating >= newdev->rating) @@ -226,6 +244,8 @@ static int tick_check_new_device(struct clock_event_device *newdev) } clockevents_exchange_device(curdev, newdev); tick_setup_device(td, newdev, cpu, cpumask); + if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) + tick_oneshot_notify(); spin_unlock_irqrestore(&tick_device_lock, flags); return NOTIFY_STOP; @@ -285,7 +305,13 @@ static int tick_notify(struct notifier_block *nb, unsigned long reason, tick_broadcast_on_off(reason, dev); break; + case CLOCK_EVT_NOTIFY_BROADCAST_ENTER: + case CLOCK_EVT_NOTIFY_BROADCAST_EXIT: + tick_broadcast_oneshot_control(reason); + break; + case CLOCK_EVT_NOTIFY_CPU_DEAD: + tick_shutdown_broadcast_oneshot(dev); tick_shutdown_broadcast(dev); tick_shutdown(dev); break; diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index 9272f446b21c..54861a0f29ff 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -10,12 +10,57 @@ extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast); extern void tick_handle_periodic(struct clock_event_device *dev); /* + * NO_HZ / high resolution timer shared code + */ +#ifdef CONFIG_TICK_ONESHOT +extern void tick_setup_oneshot(struct clock_event_device *newdev, + void (*handler)(struct clock_event_device *), + ktime_t nextevt); +extern int tick_program_event(ktime_t expires, int force); +extern void tick_oneshot_notify(void); +extern int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)); + +# ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST +extern void tick_broadcast_setup_oneshot(struct clock_event_device *bc); +extern void tick_broadcast_oneshot_control(unsigned long reason); +extern void tick_broadcast_switch_to_oneshot(void); +extern void tick_shutdown_broadcast_oneshot(unsigned int *cpup); +# else /* BROADCAST */ +static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) +{ + BUG(); +} +static inline void tick_broadcast_oneshot_control(unsigned long reason) { } +static inline void tick_broadcast_switch_to_oneshot(void) { } +static inline void tick_shutdown_broadcast_oneshot(unsigned int *cpup) { } +# endif /* !BROADCAST */ + +#else /* !ONESHOT */ +static inline +void tick_setup_oneshot(struct clock_event_device *newdev, + void (*handler)(struct clock_event_device *), + ktime_t nextevt) +{ + BUG(); +} +static inline int tick_program_event(ktime_t expires, int force) +{ + return 0; +} +static inline void tick_oneshot_notify(void) { } +static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) +{ + BUG(); +} +static inline void tick_broadcast_oneshot_control(unsigned long reason) { } +static inline void tick_shutdown_broadcast_oneshot(unsigned int *cpup) { } +#endif /* !TICK_ONESHOT */ + +/* * Broadcasting support */ #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST extern int tick_do_broadcast(cpumask_t mask); -extern struct tick_device tick_broadcast_device; -extern spinlock_t tick_broadcast_lock; extern int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu); extern int tick_check_broadcast_device(struct clock_event_device *dev); diff --git a/kernel/time/tick-oneshot.c b/kernel/time/tick-oneshot.c new file mode 100644 index 000000000000..2e8b7ff863cc --- /dev/null +++ b/kernel/time/tick-oneshot.c @@ -0,0 +1,84 @@ +/* + * linux/kernel/time/tick-oneshot.c + * + * This file contains functions which manage high resolution tick + * related events. + * + * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> + * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar + * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner + * + * This code is licenced under the GPL version 2. For details see + * kernel-base/COPYING. + */ +#include <linux/cpu.h> +#include <linux/err.h> +#include <linux/hrtimer.h> +#include <linux/irq.h> +#include <linux/percpu.h> +#include <linux/profile.h> +#include <linux/sched.h> +#include <linux/tick.h> + +#include "tick-internal.h" + +/** + * tick_program_event + */ +int tick_program_event(ktime_t expires, int force) +{ + struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; + ktime_t now = ktime_get(); + + while (1) { + int ret = clockevents_program_event(dev, expires, now); + + if (!ret || !force) + return ret; + now = ktime_get(); + expires = ktime_add(now, ktime_set(0, dev->min_delta_ns)); + } +} + +/** + * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz) + */ +void tick_setup_oneshot(struct clock_event_device *newdev, + void (*handler)(struct clock_event_device *), + ktime_t next_event) +{ + newdev->event_handler = handler; + clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT); + clockevents_program_event(newdev, next_event, ktime_get()); +} + +/** + * tick_switch_to_oneshot - switch to oneshot mode + */ +int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)) +{ + struct tick_device *td = &__get_cpu_var(tick_cpu_device); + struct clock_event_device *dev = td->evtdev; + + if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) || + !tick_device_is_functional(dev)) + return -EINVAL; + + td->mode = TICKDEV_MODE_ONESHOT; + dev->event_handler = handler; + clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); + tick_broadcast_switch_to_oneshot(); + return 0; +} + +#ifdef CONFIG_HIGH_RES_TIMERS +/** + * tick_init_highres - switch to high resolution mode + * + * Called with interrupts disabled. + */ +int tick_init_highres(void) +{ + return tick_switch_to_oneshot(hrtimer_interrupt); +} +#endif diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c new file mode 100644 index 000000000000..99d35e2af182 --- /dev/null +++ b/kernel/time/tick-sched.c @@ -0,0 +1,558 @@ +/* + * linux/kernel/time/tick-sched.c + * + * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> + * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar + * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner + * + * No idle tick implementation for low and high resolution timers + * + * Started by: Thomas Gleixner and Ingo Molnar + * + * For licencing details see kernel-base/COPYING + */ +#include <linux/cpu.h> +#include <linux/err.h> +#include <linux/hrtimer.h> +#include <linux/interrupt.h> +#include <linux/kernel_stat.h> +#include <linux/percpu.h> +#include <linux/profile.h> +#include <linux/sched.h> +#include <linux/tick.h> + +#include "tick-internal.h" + +/* + * Per cpu nohz control structure + */ +static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched); + +/* + * The time, when the last jiffy update happened. Protected by xtime_lock. + */ +static ktime_t last_jiffies_update; + +/* + * Must be called with interrupts disabled ! + */ +static void tick_do_update_jiffies64(ktime_t now) +{ + unsigned long ticks = 0; + ktime_t delta; + + /* Reevalute with xtime_lock held */ + write_seqlock(&xtime_lock); + + delta = ktime_sub(now, last_jiffies_update); + if (delta.tv64 >= tick_period.tv64) { + + delta = ktime_sub(delta, tick_period); + last_jiffies_update = ktime_add(last_jiffies_update, + tick_period); + + /* Slow path for long timeouts */ + if (unlikely(delta.tv64 >= tick_period.tv64)) { + s64 incr = ktime_to_ns(tick_period); + + ticks = ktime_divns(delta, incr); + + last_jiffies_update = ktime_add_ns(last_jiffies_update, + incr * ticks); + } + do_timer(++ticks); + } + write_sequnlock(&xtime_lock); +} + +/* + * Initialize and return retrieve the jiffies update. + */ +static ktime_t tick_init_jiffy_update(void) +{ + ktime_t period; + + write_seqlock(&xtime_lock); + /* Did we start the jiffies update yet ? */ + if (last_jiffies_update.tv64 == 0) + last_jiffies_update = tick_next_period; + period = last_jiffies_update; + write_sequnlock(&xtime_lock); + return period; +} + +/* + * NOHZ - aka dynamic tick functionality + */ +#ifdef CONFIG_NO_HZ +/* + * NO HZ enabled ? + */ +static int tick_nohz_enabled __read_mostly = 1; + +/* + * Enable / Disable tickless mode + */ +static int __init setup_tick_nohz(char *str) +{ + if (!strcmp(str, "off")) + tick_nohz_enabled = 0; + else if (!strcmp(str, "on")) + tick_nohz_enabled = 1; + else + return 0; + return 1; +} + +__setup("nohz=", setup_tick_nohz); + +/** + * tick_nohz_update_jiffies - update jiffies when idle was interrupted + * + * Called from interrupt entry when the CPU was idle + * + * In case the sched_tick was stopped on this CPU, we have to check if jiffies + * must be updated. Otherwise an interrupt handler could use a stale jiffy + * value. We do this unconditionally on any cpu, as we don't know whether the + * cpu, which has the update task assigned is in a long sleep. + */ +void tick_nohz_update_jiffies(void) +{ + int cpu = smp_processor_id(); + struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); + unsigned long flags; + ktime_t now; + + if (!ts->tick_stopped) + return; + + cpu_clear(cpu, nohz_cpu_mask); + now = ktime_get(); + + local_irq_save(flags); + tick_do_update_jiffies64(now); + local_irq_restore(flags); +} + +/** + * tick_nohz_stop_sched_tick - stop the idle tick from the idle task + * + * When the next event is more than a tick into the future, stop the idle tick + * Called either from the idle loop or from irq_exit() when an idle period was + * just interrupted by an interrupt which did not cause a reschedule. + */ +void tick_nohz_stop_sched_tick(void) +{ + unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags; + struct tick_sched *ts; + ktime_t last_update, expires, now, delta; + int cpu; + + local_irq_save(flags); + + cpu = smp_processor_id(); + ts = &per_cpu(tick_cpu_sched, cpu); + + if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) + goto end; + + if (need_resched()) + goto end; + + cpu = smp_processor_id(); + BUG_ON(local_softirq_pending()); + + now = ktime_get(); + /* + * When called from irq_exit we need to account the idle sleep time + * correctly. + */ + if (ts->tick_stopped) { + delta = ktime_sub(now, ts->idle_entrytime); + ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); + } + + ts->idle_entrytime = now; + ts->idle_calls++; + + /* Read jiffies and the time when jiffies were updated last */ + do { + seq = read_seqbegin(&xtime_lock); + last_update = last_jiffies_update; + last_jiffies = jiffies; + } while (read_seqretry(&xtime_lock, seq)); + + /* Get the next timer wheel timer */ + next_jiffies = get_next_timer_interrupt(last_jiffies); + delta_jiffies = next_jiffies - last_jiffies; + + /* + * Do not stop the tick, if we are only one off + * or if the cpu is required for rcu + */ + if (!ts->tick_stopped && (delta_jiffies == 1 || rcu_needs_cpu(cpu))) + goto out; + + /* Schedule the tick, if we are at least one jiffie off */ + if ((long)delta_jiffies >= 1) { + + if (rcu_needs_cpu(cpu)) + delta_jiffies = 1; + else + cpu_set(cpu, nohz_cpu_mask); + /* + * nohz_stop_sched_tick can be called several times before + * the 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. + */ + if (!ts->tick_stopped) { + ts->idle_tick = ts->sched_timer.expires; + ts->tick_stopped = 1; + ts->idle_jiffies = last_jiffies; + } + /* + * calculate the expiry time for the next timer wheel + * timer + */ + expires = ktime_add_ns(last_update, tick_period.tv64 * + delta_jiffies); + ts->idle_expires = expires; + ts->idle_sleeps++; + + if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { + hrtimer_start(&ts->sched_timer, expires, + HRTIMER_MODE_ABS); + /* Check, if the timer was already in the past */ + if (hrtimer_active(&ts->sched_timer)) + goto out; + } else if(!tick_program_event(expires, 0)) + goto out; + /* + * We are past the event already. So we crossed a + * jiffie boundary. Update jiffies and raise the + * softirq. + */ + tick_do_update_jiffies64(ktime_get()); + cpu_clear(cpu, nohz_cpu_mask); + } + raise_softirq_irqoff(TIMER_SOFTIRQ); +out: + ts->next_jiffies = next_jiffies; + ts->last_jiffies = last_jiffies; +end: + local_irq_restore(flags); +} + +/** + * nohz_restart_sched_tick - restart the idle tick from the idle task + * + * Restart the idle tick when the CPU is woken up from idle + */ +void tick_nohz_restart_sched_tick(void) +{ + int cpu = smp_processor_id(); + struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); + unsigned long ticks; + ktime_t now, delta; + + if (!ts->tick_stopped) + return; + + /* Update jiffies first */ + now = ktime_get(); + + local_irq_disable(); + tick_do_update_jiffies64(now); + cpu_clear(cpu, nohz_cpu_mask); + + /* Account the idle time */ + delta = ktime_sub(now, ts->idle_entrytime); + ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); + + /* + * We stopped the tick in idle. Update process times would miss the + * time we slept as update_process_times does only a 1 tick + * accounting. Enforce that this is accounted to idle ! + */ + ticks = jiffies - ts->idle_jiffies; + /* + * We might be one off. Do not randomly account a huge number of ticks! + */ + if (ticks && ticks < LONG_MAX) { + add_preempt_count(HARDIRQ_OFFSET); + account_system_time(current, HARDIRQ_OFFSET, + jiffies_to_cputime(ticks)); + sub_preempt_count(HARDIRQ_OFFSET); + } + + /* + * Cancel the scheduled timer and restore the tick + */ + ts->tick_stopped = 0; + hrtimer_cancel(&ts->sched_timer); + ts->sched_timer.expires = ts->idle_tick; + + while (1) { + /* Forward the time to expire in the future */ + hrtimer_forward(&ts->sched_timer, now, tick_period); + + if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { + hrtimer_start(&ts->sched_timer, + ts->sched_timer.expires, + HRTIMER_MODE_ABS); + /* Check, if the timer was already in the past */ + if (hrtimer_active(&ts->sched_timer)) + break; + } else { + if (!tick_program_event(ts->sched_timer.expires, 0)) + break; + } + /* Update jiffies and reread time */ + tick_do_update_jiffies64(now); + now = ktime_get(); + } + local_irq_enable(); +} + +static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now) +{ + hrtimer_forward(&ts->sched_timer, now, tick_period); + return tick_program_event(ts->sched_timer.expires, 0); +} + +/* + * The nohz low res interrupt handler + */ +static void tick_nohz_handler(struct clock_event_device *dev) +{ + struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); + struct pt_regs *regs = get_irq_regs(); + ktime_t now = ktime_get(); + + dev->next_event.tv64 = KTIME_MAX; + + /* Check, if the jiffies need an update */ + tick_do_update_jiffies64(now); + + /* + * When we are idle and the tick is stopped, we have to touch + * the watchdog as we might not schedule for a really long + * time. This happens on complete idle SMP systems while + * waiting on the login prompt. We also increment the "start + * of idle" jiffy stamp so the idle accounting adjustment we + * do when we go busy again does not account too much ticks. + */ + if (ts->tick_stopped) { + touch_softlockup_watchdog(); + ts->idle_jiffies++; + } + + update_process_times(user_mode(regs)); + profile_tick(CPU_PROFILING); + + /* Do not restart, when we are in the idle loop */ + if (ts->tick_stopped) + return; + + while (tick_nohz_reprogram(ts, now)) { + now = ktime_get(); + tick_do_update_jiffies64(now); + } +} + +/** + * tick_nohz_switch_to_nohz - switch to nohz mode + */ +static void tick_nohz_switch_to_nohz(void) +{ + struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); + ktime_t next; + + if (!tick_nohz_enabled) + return; + + local_irq_disable(); + if (tick_switch_to_oneshot(tick_nohz_handler)) { + local_irq_enable(); + return; + } + + ts->nohz_mode = NOHZ_MODE_LOWRES; + + /* + * Recycle the hrtimer in ts, so we can share the + * hrtimer_forward with the highres code. + */ + hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); + /* Get the next period */ + next = tick_init_jiffy_update(); + + for (;;) { + ts->sched_timer.expires = next; + if (!tick_program_event(next, 0)) + break; + next = ktime_add(next, tick_period); + } + local_irq_enable(); + + printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n", + smp_processor_id()); +} + +#else + +static inline void tick_nohz_switch_to_nohz(void) { } + +#endif /* NO_HZ */ + +/* + * High resolution timer specific code + */ +#ifdef CONFIG_HIGH_RES_TIMERS +/* + * We rearm the timer until we get disabled by the idle code + * Called with interrupts disabled and timer->base->cpu_base->lock held. + */ +static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) +{ + struct tick_sched *ts = + container_of(timer, struct tick_sched, sched_timer); + struct hrtimer_cpu_base *base = timer->base->cpu_base; + struct pt_regs *regs = get_irq_regs(); + ktime_t now = ktime_get(); + + /* Check, if the jiffies need an update */ + tick_do_update_jiffies64(now); + + /* + * Do not call, when we are not in irq context and have + * no valid regs pointer + */ + if (regs) { + /* + * When we are idle and the tick is stopped, we have to touch + * the watchdog as we might not schedule for a really long + * time. This happens on complete idle SMP systems while + * waiting on the login prompt. We also increment the "start of + * idle" jiffy stamp so the idle accounting adjustment we do + * when we go busy again does not account too much ticks. + */ + if (ts->tick_stopped) { + touch_softlockup_watchdog(); + ts->idle_jiffies++; + } + /* + * update_process_times() might take tasklist_lock, hence + * drop the base lock. sched-tick hrtimers are per-CPU and + * never accessible by userspace APIs, so this is safe to do. + */ + spin_unlock(&base->lock); + update_process_times(user_mode(regs)); + profile_tick(CPU_PROFILING); + spin_lock(&base->lock); + } + + /* Do not restart, when we are in the idle loop */ + if (ts->tick_stopped) + return HRTIMER_NORESTART; + + hrtimer_forward(timer, now, tick_period); + + return HRTIMER_RESTART; +} + +/** + * tick_setup_sched_timer - setup the tick emulation timer + */ +void tick_setup_sched_timer(void) +{ + struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); + ktime_t now = ktime_get(); + + /* + * Emulate tick processing via per-CPU hrtimers: + */ + hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); + ts->sched_timer.function = tick_sched_timer; + ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ; + + /* Get the next period */ + ts->sched_timer.expires = tick_init_jiffy_update(); + + for (;;) { + hrtimer_forward(&ts->sched_timer, now, tick_period); + hrtimer_start(&ts->sched_timer, ts->sched_timer.expires, + HRTIMER_MODE_ABS); + /* Check, if the timer was already in the past */ + if (hrtimer_active(&ts->sched_timer)) + break; + now = ktime_get(); + } + +#ifdef CONFIG_NO_HZ + if (tick_nohz_enabled) + ts->nohz_mode = NOHZ_MODE_HIGHRES; +#endif +} + +void tick_cancel_sched_timer(int cpu) +{ + struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); + + if (ts->sched_timer.base) + hrtimer_cancel(&ts->sched_timer); + ts->tick_stopped = 0; + ts->nohz_mode = NOHZ_MODE_INACTIVE; +} +#endif /* HIGH_RES_TIMERS */ + +/** + * Async notification about clocksource changes + */ +void tick_clock_notify(void) +{ + int cpu; + + for_each_possible_cpu(cpu) + set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); +} + +/* + * Async notification about clock event changes + */ +void tick_oneshot_notify(void) +{ + struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); + + set_bit(0, &ts->check_clocks); +} + +/** + * Check, if a change happened, which makes oneshot possible. + * + * Called cyclic from the hrtimer softirq (driven by the timer + * softirq) allow_nohz signals, that we can switch into low-res nohz + * mode, because high resolution timers are disabled (either compile + * or runtime). + */ +int tick_check_oneshot_change(int allow_nohz) +{ + struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); + + if (!test_and_clear_bit(0, &ts->check_clocks)) + return 0; + + if (ts->nohz_mode != NOHZ_MODE_INACTIVE) + return 0; + + if (!timekeeping_is_continuous() || !tick_is_oneshot_available()) + return 0; + + if (!allow_nohz) + return 1; + + tick_nohz_switch_to_nohz(); + return 0; +} |
