/* * 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 <asm/irq_regs.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; struct tick_sched *tick_get_tick_sched(int cpu){ return &per_cpu(tick_cpu_sched, cpu);} /* * 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(); if (unlikely(local_softirq_pending())) printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n", 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; if (rcu_needs_cpu(cpu)) delta_jiffies = 1; /* * 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) goto out; /* Schedule the tick, if we are at least one jiffie off */ if ((long)delta_jiffies >= 1) { if (delta_jiffies > 1) 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();Lines 1–500 of 567. 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/* * 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 <asm/irq_regs.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; struct tick_sched *tick_get_tick_sched(int cpu) { return &per_cpu(tick_cpu_sched, cpu); } /* * 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(); if (unlikely(local_softirq_pending())) printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n", 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; if (rcu_needs_cpu(cpu)) delta_jiffies = 1; /* * 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) goto out; /* Schedule the tick, if we are at least one jiffie off */ if ((long)delta_jiffies >= 1) { if (delta_jiffies > 1) 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();