diff options
Diffstat (limited to 'kernel/time/tick-sched.c')
-rw-r--r-- | kernel/time/tick-sched.c | 144 |
1 files changed, 101 insertions, 43 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index a87b0468568b..342fc9ccab46 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -20,6 +20,7 @@ #include <linux/profile.h> #include <linux/sched.h> #include <linux/tick.h> +#include <linux/module.h> #include <asm/irq_regs.h> @@ -75,6 +76,9 @@ static void tick_do_update_jiffies64(ktime_t now) incr * ticks); } do_timer(++ticks); + + /* Keep the tick_next_period variable up to date */ + tick_next_period = ktime_add(last_jiffies_update, tick_period); } write_sequnlock(&xtime_lock); } @@ -151,7 +155,7 @@ void tick_nohz_update_jiffies(void) touch_softlockup_watchdog(); } -void tick_nohz_stop_idle(int cpu) +static void tick_nohz_stop_idle(int cpu) { struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); @@ -187,9 +191,17 @@ u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) { struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); - *last_update_time = ktime_to_us(ts->idle_lastupdate); + if (!tick_nohz_enabled) + return -1; + + if (ts->idle_active) + *last_update_time = ktime_to_us(ts->idle_lastupdate); + else + *last_update_time = ktime_to_us(ktime_get()); + return ktime_to_us(ts->idle_sleeptime); } +EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); /** * tick_nohz_stop_sched_tick - stop the idle tick from the idle task @@ -221,7 +233,7 @@ void tick_nohz_stop_sched_tick(int inidle) */ if (unlikely(!cpu_online(cpu))) { if (cpu == tick_do_timer_cpu) - tick_do_timer_cpu = -1; + tick_do_timer_cpu = TICK_DO_TIMER_NONE; } if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) @@ -258,7 +270,7 @@ void tick_nohz_stop_sched_tick(int inidle) next_jiffies = get_next_timer_interrupt(last_jiffies); delta_jiffies = next_jiffies - last_jiffies; - if (rcu_needs_cpu(cpu)) + if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu)) delta_jiffies = 1; /* * Do not stop the tick, if we are only one off @@ -288,7 +300,7 @@ void tick_nohz_stop_sched_tick(int inidle) goto out; } - ts->idle_tick = ts->sched_timer.expires; + ts->idle_tick = hrtimer_get_expires(&ts->sched_timer); ts->tick_stopped = 1; ts->idle_jiffies = last_jiffies; rcu_enter_nohz(); @@ -303,7 +315,7 @@ void tick_nohz_stop_sched_tick(int inidle) * invoked. */ if (cpu == tick_do_timer_cpu) - tick_do_timer_cpu = -1; + tick_do_timer_cpu = TICK_DO_TIMER_NONE; ts->idle_sleeps++; @@ -365,6 +377,32 @@ ktime_t tick_nohz_get_sleep_length(void) return ts->sleep_length; } +static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) +{ + hrtimer_cancel(&ts->sched_timer); + hrtimer_set_expires(&ts->sched_timer, 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_expires(&ts->sched_timer, + HRTIMER_MODE_ABS); + /* Check, if the timer was already in the past */ + if (hrtimer_active(&ts->sched_timer)) + break; + } else { + if (!tick_program_event( + hrtimer_get_expires(&ts->sched_timer), 0)) + break; + } + /* Update jiffies and reread time */ + tick_do_update_jiffies64(now); + now = ktime_get(); + } +} + /** * tick_nohz_restart_sched_tick - restart the idle tick from the idle task * @@ -418,35 +456,16 @@ void tick_nohz_restart_sched_tick(void) */ ts->tick_stopped = 0; ts->idle_exittime = now; - 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); + tick_nohz_restart(ts, now); - 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); + return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0); } /* @@ -468,7 +487,7 @@ static void tick_nohz_handler(struct clock_event_device *dev) * this duty, then the jiffies update is still serialized by * xtime_lock. */ - if (unlikely(tick_do_timer_cpu == -1)) + if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) tick_do_timer_cpu = cpu; /* Check, if the jiffies need an update */ @@ -491,10 +510,6 @@ static void tick_nohz_handler(struct clock_event_device *dev) 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); @@ -529,7 +544,7 @@ static void tick_nohz_switch_to_nohz(void) next = tick_init_jiffy_update(); for (;;) { - ts->sched_timer.expires = next; + hrtimer_set_expires(&ts->sched_timer, next); if (!tick_program_event(next, 0)) break; next = ktime_add(next, tick_period); @@ -540,6 +555,41 @@ static void tick_nohz_switch_to_nohz(void) smp_processor_id()); } +/* + * When NOHZ is enabled and the tick is stopped, we need to kick the + * tick timer from irq_enter() so that the jiffies update is kept + * alive during long running softirqs. That's ugly as hell, but + * correctness is key even if we need to fix the offending softirq in + * the first place. + * + * Note, this is different to tick_nohz_restart. We just kick the + * timer and do not touch the other magic bits which need to be done + * when idle is left. + */ +static void tick_nohz_kick_tick(int cpu) +{ +#if 0 + /* Switch back to 2.6.27 behaviour */ + + struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); + ktime_t delta, now; + + if (!ts->tick_stopped) + return; + + /* + * Do not touch the tick device, when the next expiry is either + * already reached or less/equal than the tick period. + */ + now = ktime_get(); + delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now); + if (delta.tv64 <= tick_period.tv64) + return; + + tick_nohz_restart(ts, now); +#endif +} + #else static inline void tick_nohz_switch_to_nohz(void) { } @@ -547,6 +597,19 @@ static inline void tick_nohz_switch_to_nohz(void) { } #endif /* NO_HZ */ /* + * Called from irq_enter to notify about the possible interruption of idle() + */ +void tick_check_idle(int cpu) +{ + tick_check_oneshot_broadcast(cpu); +#ifdef CONFIG_NO_HZ + tick_nohz_stop_idle(cpu); + tick_nohz_update_jiffies(); + tick_nohz_kick_tick(cpu); +#endif +} + +/* * High resolution timer specific code */ #ifdef CONFIG_HIGH_RES_TIMERS @@ -570,7 +633,7 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) * this duty, then the jiffies update is still serialized by * xtime_lock. */ - if (unlikely(tick_do_timer_cpu == -1)) + if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) tick_do_timer_cpu = cpu; #endif @@ -599,10 +662,6 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) profile_tick(CPU_PROFILING); } - /* 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; @@ -622,19 +681,18 @@ void tick_setup_sched_timer(void) */ 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; + ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_PERCPU; /* Get the next period (per cpu) */ - ts->sched_timer.expires = tick_init_jiffy_update(); + hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update()); offset = ktime_to_ns(tick_period) >> 1; do_div(offset, num_possible_cpus()); offset *= smp_processor_id(); - ts->sched_timer.expires = ktime_add_ns(ts->sched_timer.expires, offset); + hrtimer_add_expires_ns(&ts->sched_timer, offset); for (;;) { hrtimer_forward(&ts->sched_timer, now, tick_period); - hrtimer_start(&ts->sched_timer, ts->sched_timer.expires, - HRTIMER_MODE_ABS); + hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS); /* Check, if the timer was already in the past */ if (hrtimer_active(&ts->sched_timer)) break; |