in certain environments such as networked servers or
real-time systems.
+ nohz= [KNL] Boottime enable/disable dynamic ticks
+ Valid arguments: on, off
+ Default: on
+
noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
noirqdebug [IA-32] Disables the code which attempts to detect and
* always balanced, so the interrupted value of ->hardirq_context
* will always be restored.
*/
+#define __irq_enter() \
+ do { \
+ account_system_vtime(current); \
+ add_preempt_count(HARDIRQ_OFFSET); \
+ trace_hardirq_enter(); \
+ } while (0)
+
+/*
+ * Enter irq context (on NO_HZ, update jiffies):
+ */
extern void irq_enter(void);
/*
*/
extern void irq_exit(void);
-#define nmi_enter() do { lockdep_off(); irq_enter(); } while (0)
+#define nmi_enter() do { lockdep_off(); __irq_enter(); } while (0)
#define nmi_exit() do { __irq_exit(); lockdep_on(); } while (0)
#endif /* LINUX_HARDIRQ_H */
/* Bootup initialization: */
extern void __init hrtimers_init(void);
+#if BITS_PER_LONG < 64
+extern unsigned long ktime_divns(const ktime_t kt, s64 div);
+#else /* BITS_PER_LONG < 64 */
+# define ktime_divns(kt, div) (unsigned long)((kt).tv64 / (div))
+#endif
+
#endif
enum tick_device_mode mode;
};
+enum tick_nohz_mode {
+ NOHZ_MODE_INACTIVE,
+ NOHZ_MODE_LOWRES,
+ NOHZ_MODE_HIGHRES,
+};
+
+/**
+ * struct tick_sched - sched tick emulation and no idle tick control/stats
+ * @sched_timer: hrtimer to schedule the periodic tick in high
+ * resolution mode
+ * @idle_tick: Store the last idle tick expiry time when the tick
+ * timer is modified for idle sleeps. This is necessary
+ * to resume the tick timer operation in the timeline
+ * when the CPU returns from idle
+ * @tick_stopped: Indicator that the idle tick has been stopped
+ * @idle_jiffies: jiffies at the entry to idle for idle time accounting
+ * @idle_calls: Total number of idle calls
+ * @idle_sleeps: Number of idle calls, where the sched tick was stopped
+ * @idle_entrytime: Time when the idle call was entered
+ * @idle_sleeptime: Sum of the time slept in idle with sched tick stopped
+ */
+struct tick_sched {
+ struct hrtimer sched_timer;
+ unsigned long check_clocks;
+ enum tick_nohz_mode nohz_mode;
+ ktime_t idle_tick;
+ int tick_stopped;
+ unsigned long idle_jiffies;
+ unsigned long idle_calls;
+ unsigned long idle_sleeps;
+ ktime_t idle_entrytime;
+ ktime_t idle_sleeptime;
+ unsigned long last_jiffies;
+ unsigned long next_jiffies;
+ ktime_t idle_expires;
+};
+
extern void __init tick_init(void);
+extern int tick_is_oneshot_available(void);
+
+# ifdef CONFIG_HIGH_RES_TIMERS
+extern int tick_init_highres(void);
+extern int tick_program_event(ktime_t expires, int force);
+extern void tick_setup_sched_timer(void);
+extern void tick_cancel_sched_timer(int cpu);
+# else
+static inline void tick_cancel_sched_timer(int cpu) { }
+# endif /* HIGHRES */
-#else
+# ifdef CONFIG_TICK_ONESHOT
+extern void tick_clock_notify(void);
+extern int tick_check_oneshot_change(int allow_nohz);
+extern struct tick_sched *tick_get_tick_sched(int cpu);
+# else
+static inline void tick_clock_notify(void) { }
+static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }
+# endif
+#else /* CONFIG_GENERIC_CLOCKEVENTS */
static inline void tick_init(void) { }
+static inline void tick_cancel_sched_timer(int cpu) { }
+static inline void tick_clock_notify(void) { }
+static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }
+#endif /* !CONFIG_GENERIC_CLOCKEVENTS */
-#endif
+# ifdef CONFIG_NO_HZ
+extern void tick_nohz_stop_sched_tick(void);
+extern void tick_nohz_restart_sched_tick(void);
+extern void tick_nohz_update_jiffies(void);
+# else
+static inline void tick_nohz_stop_sched_tick(void) { }
+static inline void tick_nohz_restart_sched_tick(void) { }
+static inline void tick_nohz_update_jiffies(void) { }
+# endif /* !NO_HZ */
#endif
* linux/kernel/hrtimer.c
*
* Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
- * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
- * Copyright(C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
+ * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
+ * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
*
* High-resolution kernel timers
*
#include <linux/notifier.h>
#include <linux/syscalls.h>
#include <linux/interrupt.h>
+#include <linux/tick.h>
#include <asm/uaccess.h>
/*
* Divide a ktime value by a nanosecond value
*/
-static unsigned long ktime_divns(const ktime_t kt, s64 div)
+unsigned long ktime_divns(const ktime_t kt, s64 div)
{
u64 dclc, inc, dns;
int sft = 0;
return (unsigned long) dclc;
}
-
-#else /* BITS_PER_LONG < 64 */
-# define ktime_divns(kt, div) (unsigned long)((kt).tv64 / (div))
#endif /* BITS_PER_LONG >= 64 */
/*
struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
int i;
+ /*
+ * This _is_ ugly: We have to check in the softirq context,
+ * whether we can switch to highres and / or nohz mode. The
+ * clocksource switch happens in the timer interrupt with
+ * xtime_lock held. Notification from there only sets the
+ * check bit in the tick_oneshot code, otherwise we might
+ * deadlock vs. xtime_lock.
+ */
+ tick_check_oneshot_change(1);
+
hrtimer_get_softirq_time(cpu_base);
for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
#include <linux/kthread.h>
#include <linux/rcupdate.h>
#include <linux/smp.h>
+#include <linux/tick.h>
#include <asm/irq.h>
/*
*/
void irq_enter(void)
{
- account_system_vtime(current);
- add_preempt_count(HARDIRQ_OFFSET);
- trace_hardirq_enter();
+ __irq_enter();
+#ifdef CONFIG_NO_HZ
+ if (idle_cpu(smp_processor_id()))
+ tick_nohz_update_jiffies();
+#endif
}
#ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
sub_preempt_count(IRQ_EXIT_OFFSET);
if (!in_interrupt() && local_softirq_pending())
invoke_softirq();
+
+#ifdef CONFIG_NO_HZ
+ /* Make sure that timer wheel updates are propagated */
+ if (!in_interrupt() && idle_cpu(smp_processor_id()) && !need_resched())
+ tick_nohz_stop_sched_tick();
+#endif
preempt_enable_no_resched();
}
--- /dev/null
+#
+# 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.
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
#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;
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;
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
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);
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
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
*/
if (td->mode == TICKDEV_MODE_PERIODIC)
tick_setup_periodic(newdev, 0);
+ else
+ tick_setup_oneshot(newdev, handler, next_event);
}
/*
* feature.
*/
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
*/
}
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;
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;
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);
--- /dev/null
+/*
+ * 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
--- /dev/null
+/*
+ * 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;
+}
#include <linux/cpu.h>
#include <linux/syscalls.h>
#include <linux/delay.h>
-#include <linux/clockchips.h>
+#include <linux/tick.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
clock->xtime_nsec = 0;
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
+ tick_clock_notify();
+
printk(KERN_INFO "Time: %s clocksource has been installed.\n",
clock->name);
}
write_sequnlock_irqrestore(&xtime_lock, flags);
}
-
/* flag for if timekeeping is suspended */
static int timekeeping_suspended;
/* time in seconds when suspend began */
projects / linux-drm-fsl-dcu.git / commitdiff