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1484 lines
37 KiB
1484 lines
37 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Copyright(C) 2005-2006, Thomas Gleixner <[email protected]> |
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* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar |
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* Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner |
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* |
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* No idle tick implementation for low and high resolution timers |
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* |
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* Started by: Thomas Gleixner and Ingo Molnar |
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*/ |
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#include <linux/cpu.h> |
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#include <linux/err.h> |
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#include <linux/hrtimer.h> |
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#include <linux/interrupt.h> |
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#include <linux/kernel_stat.h> |
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#include <linux/percpu.h> |
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#include <linux/nmi.h> |
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#include <linux/profile.h> |
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#include <linux/sched/signal.h> |
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#include <linux/sched/clock.h> |
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#include <linux/sched/stat.h> |
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#include <linux/sched/nohz.h> |
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#include <linux/sched/loadavg.h> |
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#include <linux/module.h> |
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#include <linux/irq_work.h> |
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#include <linux/posix-timers.h> |
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#include <linux/context_tracking.h> |
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#include <linux/mm.h> |
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#include <asm/irq_regs.h> |
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#include "tick-internal.h" |
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#include <trace/events/timer.h> |
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|
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/* |
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* Per-CPU nohz control structure |
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*/ |
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static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched); |
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struct tick_sched *tick_get_tick_sched(int cpu) |
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{ |
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return &per_cpu(tick_cpu_sched, cpu); |
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} |
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#if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS) |
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/* |
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* The time, when the last jiffy update happened. Write access must hold |
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* jiffies_lock and jiffies_seq. tick_nohz_next_event() needs to get a |
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* consistent view of jiffies and last_jiffies_update. |
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*/ |
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static ktime_t last_jiffies_update; |
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|
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/* |
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* Must be called with interrupts disabled ! |
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*/ |
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static void tick_do_update_jiffies64(ktime_t now) |
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{ |
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unsigned long ticks = 1; |
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ktime_t delta, nextp; |
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/* |
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* 64bit can do a quick check without holding jiffies lock and |
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* without looking at the sequence count. The smp_load_acquire() |
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* pairs with the update done later in this function. |
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* |
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* 32bit cannot do that because the store of tick_next_period |
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* consists of two 32bit stores and the first store could move it |
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* to a random point in the future. |
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*/ |
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if (IS_ENABLED(CONFIG_64BIT)) { |
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if (ktime_before(now, smp_load_acquire(&tick_next_period))) |
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return; |
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} else { |
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unsigned int seq; |
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/* |
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* Avoid contention on jiffies_lock and protect the quick |
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* check with the sequence count. |
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*/ |
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do { |
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seq = read_seqcount_begin(&jiffies_seq); |
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nextp = tick_next_period; |
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} while (read_seqcount_retry(&jiffies_seq, seq)); |
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if (ktime_before(now, nextp)) |
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return; |
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} |
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/* Quick check failed, i.e. update is required. */ |
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raw_spin_lock(&jiffies_lock); |
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/* |
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* Reevaluate with the lock held. Another CPU might have done the |
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* update already. |
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*/ |
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if (ktime_before(now, tick_next_period)) { |
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raw_spin_unlock(&jiffies_lock); |
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return; |
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} |
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write_seqcount_begin(&jiffies_seq); |
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delta = ktime_sub(now, tick_next_period); |
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if (unlikely(delta >= TICK_NSEC)) { |
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/* Slow path for long idle sleep times */ |
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s64 incr = TICK_NSEC; |
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ticks += ktime_divns(delta, incr); |
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last_jiffies_update = ktime_add_ns(last_jiffies_update, |
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incr * ticks); |
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} else { |
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last_jiffies_update = ktime_add_ns(last_jiffies_update, |
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TICK_NSEC); |
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} |
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|
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/* Advance jiffies to complete the jiffies_seq protected job */ |
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jiffies_64 += ticks; |
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/* |
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* Keep the tick_next_period variable up to date. |
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*/ |
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nextp = ktime_add_ns(last_jiffies_update, TICK_NSEC); |
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if (IS_ENABLED(CONFIG_64BIT)) { |
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/* |
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* Pairs with smp_load_acquire() in the lockless quick |
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* check above and ensures that the update to jiffies_64 is |
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* not reordered vs. the store to tick_next_period, neither |
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* by the compiler nor by the CPU. |
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*/ |
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smp_store_release(&tick_next_period, nextp); |
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} else { |
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/* |
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* A plain store is good enough on 32bit as the quick check |
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* above is protected by the sequence count. |
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*/ |
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tick_next_period = nextp; |
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} |
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/* |
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* Release the sequence count. calc_global_load() below is not |
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* protected by it, but jiffies_lock needs to be held to prevent |
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* concurrent invocations. |
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*/ |
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write_seqcount_end(&jiffies_seq); |
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calc_global_load(); |
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raw_spin_unlock(&jiffies_lock); |
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update_wall_time(); |
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} |
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/* |
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* Initialize and return retrieve the jiffies update. |
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*/ |
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static ktime_t tick_init_jiffy_update(void) |
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{ |
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ktime_t period; |
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raw_spin_lock(&jiffies_lock); |
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write_seqcount_begin(&jiffies_seq); |
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/* Did we start the jiffies update yet ? */ |
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if (last_jiffies_update == 0) |
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last_jiffies_update = tick_next_period; |
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period = last_jiffies_update; |
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write_seqcount_end(&jiffies_seq); |
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raw_spin_unlock(&jiffies_lock); |
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return period; |
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} |
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static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now) |
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{ |
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int cpu = smp_processor_id(); |
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#ifdef CONFIG_NO_HZ_COMMON |
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/* |
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* Check if the do_timer duty was dropped. We don't care about |
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* concurrency: This happens only when the CPU in charge went |
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* into a long sleep. If two CPUs happen to assign themselves to |
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* this duty, then the jiffies update is still serialized by |
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* jiffies_lock. |
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* |
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* If nohz_full is enabled, this should not happen because the |
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* tick_do_timer_cpu never relinquishes. |
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*/ |
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if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) { |
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#ifdef CONFIG_NO_HZ_FULL |
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WARN_ON(tick_nohz_full_running); |
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#endif |
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tick_do_timer_cpu = cpu; |
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} |
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#endif |
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/* Check, if the jiffies need an update */ |
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if (tick_do_timer_cpu == cpu) |
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tick_do_update_jiffies64(now); |
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if (ts->inidle) |
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ts->got_idle_tick = 1; |
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} |
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static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) |
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{ |
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#ifdef CONFIG_NO_HZ_COMMON |
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/* |
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* When we are idle and the tick is stopped, we have to touch |
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* the watchdog as we might not schedule for a really long |
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* time. This happens on complete idle SMP systems while |
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* waiting on the login prompt. We also increment the "start of |
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* idle" jiffy stamp so the idle accounting adjustment we do |
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* when we go busy again does not account too much ticks. |
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*/ |
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if (ts->tick_stopped) { |
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touch_softlockup_watchdog_sched(); |
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if (is_idle_task(current)) |
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ts->idle_jiffies++; |
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/* |
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* In case the current tick fired too early past its expected |
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* expiration, make sure we don't bypass the next clock reprogramming |
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* to the same deadline. |
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*/ |
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ts->next_tick = 0; |
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} |
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#endif |
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update_process_times(user_mode(regs)); |
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profile_tick(CPU_PROFILING); |
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} |
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#endif |
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#ifdef CONFIG_NO_HZ_FULL |
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cpumask_var_t tick_nohz_full_mask; |
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bool tick_nohz_full_running; |
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EXPORT_SYMBOL_GPL(tick_nohz_full_running); |
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static atomic_t tick_dep_mask; |
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static bool check_tick_dependency(atomic_t *dep) |
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{ |
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int val = atomic_read(dep); |
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if (val & TICK_DEP_MASK_POSIX_TIMER) { |
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trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER); |
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return true; |
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} |
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if (val & TICK_DEP_MASK_PERF_EVENTS) { |
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trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS); |
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return true; |
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} |
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if (val & TICK_DEP_MASK_SCHED) { |
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trace_tick_stop(0, TICK_DEP_MASK_SCHED); |
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return true; |
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} |
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if (val & TICK_DEP_MASK_CLOCK_UNSTABLE) { |
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trace_tick_stop(0, TICK_DEP_MASK_CLOCK_UNSTABLE); |
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return true; |
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} |
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if (val & TICK_DEP_MASK_RCU) { |
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trace_tick_stop(0, TICK_DEP_MASK_RCU); |
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return true; |
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} |
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return false; |
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} |
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static bool can_stop_full_tick(int cpu, struct tick_sched *ts) |
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{ |
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lockdep_assert_irqs_disabled(); |
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if (unlikely(!cpu_online(cpu))) |
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return false; |
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if (check_tick_dependency(&tick_dep_mask)) |
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return false; |
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if (check_tick_dependency(&ts->tick_dep_mask)) |
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return false; |
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if (check_tick_dependency(¤t->tick_dep_mask)) |
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return false; |
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if (check_tick_dependency(¤t->signal->tick_dep_mask)) |
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return false; |
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return true; |
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} |
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static void nohz_full_kick_func(struct irq_work *work) |
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{ |
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/* Empty, the tick restart happens on tick_nohz_irq_exit() */ |
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} |
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static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = |
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IRQ_WORK_INIT_HARD(nohz_full_kick_func); |
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/* |
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* Kick this CPU if it's full dynticks in order to force it to |
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* re-evaluate its dependency on the tick and restart it if necessary. |
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* This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(), |
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* is NMI safe. |
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*/ |
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static void tick_nohz_full_kick(void) |
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{ |
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if (!tick_nohz_full_cpu(smp_processor_id())) |
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return; |
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irq_work_queue(this_cpu_ptr(&nohz_full_kick_work)); |
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} |
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/* |
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* Kick the CPU if it's full dynticks in order to force it to |
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* re-evaluate its dependency on the tick and restart it if necessary. |
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*/ |
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void tick_nohz_full_kick_cpu(int cpu) |
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{ |
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if (!tick_nohz_full_cpu(cpu)) |
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return; |
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irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu); |
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} |
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/* |
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* Kick all full dynticks CPUs in order to force these to re-evaluate |
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* their dependency on the tick and restart it if necessary. |
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*/ |
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static void tick_nohz_full_kick_all(void) |
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{ |
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int cpu; |
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if (!tick_nohz_full_running) |
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return; |
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preempt_disable(); |
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for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask) |
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tick_nohz_full_kick_cpu(cpu); |
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preempt_enable(); |
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} |
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static void tick_nohz_dep_set_all(atomic_t *dep, |
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enum tick_dep_bits bit) |
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{ |
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int prev; |
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prev = atomic_fetch_or(BIT(bit), dep); |
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if (!prev) |
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tick_nohz_full_kick_all(); |
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} |
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/* |
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* Set a global tick dependency. Used by perf events that rely on freq and |
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* by unstable clock. |
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*/ |
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void tick_nohz_dep_set(enum tick_dep_bits bit) |
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{ |
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tick_nohz_dep_set_all(&tick_dep_mask, bit); |
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} |
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void tick_nohz_dep_clear(enum tick_dep_bits bit) |
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{ |
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atomic_andnot(BIT(bit), &tick_dep_mask); |
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} |
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/* |
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* Set per-CPU tick dependency. Used by scheduler and perf events in order to |
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* manage events throttling. |
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*/ |
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void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) |
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{ |
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int prev; |
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struct tick_sched *ts; |
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ts = per_cpu_ptr(&tick_cpu_sched, cpu); |
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prev = atomic_fetch_or(BIT(bit), &ts->tick_dep_mask); |
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if (!prev) { |
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preempt_disable(); |
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/* Perf needs local kick that is NMI safe */ |
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if (cpu == smp_processor_id()) { |
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tick_nohz_full_kick(); |
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} else { |
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/* Remote irq work not NMI-safe */ |
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if (!WARN_ON_ONCE(in_nmi())) |
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tick_nohz_full_kick_cpu(cpu); |
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} |
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preempt_enable(); |
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} |
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} |
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EXPORT_SYMBOL_GPL(tick_nohz_dep_set_cpu); |
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void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) |
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{ |
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struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu); |
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atomic_andnot(BIT(bit), &ts->tick_dep_mask); |
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} |
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EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu); |
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/* |
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* Set a per-task tick dependency. RCU need this. Also posix CPU timers |
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* in order to elapse per task timers. |
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*/ |
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void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit) |
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{ |
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if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask)) { |
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if (tsk == current) { |
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preempt_disable(); |
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tick_nohz_full_kick(); |
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preempt_enable(); |
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} else { |
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/* |
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* Some future tick_nohz_full_kick_task() |
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* should optimize this. |
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*/ |
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tick_nohz_full_kick_all(); |
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} |
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} |
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} |
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EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task); |
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void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit) |
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{ |
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atomic_andnot(BIT(bit), &tsk->tick_dep_mask); |
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} |
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EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task); |
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/* |
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* Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse |
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* per process timers. |
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*/ |
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void tick_nohz_dep_set_signal(struct signal_struct *sig, enum tick_dep_bits bit) |
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{ |
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tick_nohz_dep_set_all(&sig->tick_dep_mask, bit); |
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} |
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void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit) |
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{ |
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atomic_andnot(BIT(bit), &sig->tick_dep_mask); |
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} |
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/* |
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* Re-evaluate the need for the tick as we switch the current task. |
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* It might need the tick due to per task/process properties: |
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* perf events, posix CPU timers, ... |
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*/ |
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void __tick_nohz_task_switch(void) |
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{ |
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unsigned long flags; |
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struct tick_sched *ts; |
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local_irq_save(flags); |
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if (!tick_nohz_full_cpu(smp_processor_id())) |
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goto out; |
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ts = this_cpu_ptr(&tick_cpu_sched); |
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|
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if (ts->tick_stopped) { |
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if (atomic_read(¤t->tick_dep_mask) || |
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atomic_read(¤t->signal->tick_dep_mask)) |
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tick_nohz_full_kick(); |
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} |
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out: |
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local_irq_restore(flags); |
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} |
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|
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/* Get the boot-time nohz CPU list from the kernel parameters. */ |
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void __init tick_nohz_full_setup(cpumask_var_t cpumask) |
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{ |
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alloc_bootmem_cpumask_var(&tick_nohz_full_mask); |
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cpumask_copy(tick_nohz_full_mask, cpumask); |
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tick_nohz_full_running = true; |
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} |
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EXPORT_SYMBOL_GPL(tick_nohz_full_setup); |
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|
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static int tick_nohz_cpu_down(unsigned int cpu) |
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{ |
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/* |
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* The tick_do_timer_cpu CPU handles housekeeping duty (unbound |
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* timers, workqueues, timekeeping, ...) on behalf of full dynticks |
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* CPUs. It must remain online when nohz full is enabled. |
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*/ |
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if (tick_nohz_full_running && tick_do_timer_cpu == cpu) |
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return -EBUSY; |
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return 0; |
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} |
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|
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void __init tick_nohz_init(void) |
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{ |
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int cpu, ret; |
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|
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if (!tick_nohz_full_running) |
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return; |
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|
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/* |
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* Full dynticks uses irq work to drive the tick rescheduling on safe |
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* locking contexts. But then we need irq work to raise its own |
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* interrupts to avoid circular dependency on the tick |
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*/ |
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if (!arch_irq_work_has_interrupt()) { |
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pr_warn("NO_HZ: Can't run full dynticks because arch doesn't support irq work self-IPIs\n"); |
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cpumask_clear(tick_nohz_full_mask); |
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tick_nohz_full_running = false; |
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return; |
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} |
|
|
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if (IS_ENABLED(CONFIG_PM_SLEEP_SMP) && |
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!IS_ENABLED(CONFIG_PM_SLEEP_SMP_NONZERO_CPU)) { |
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cpu = smp_processor_id(); |
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|
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if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) { |
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pr_warn("NO_HZ: Clearing %d from nohz_full range " |
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"for timekeeping\n", cpu); |
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cpumask_clear_cpu(cpu, tick_nohz_full_mask); |
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} |
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} |
|
|
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for_each_cpu(cpu, tick_nohz_full_mask) |
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context_tracking_cpu_set(cpu); |
|
|
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ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, |
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"kernel/nohz:predown", NULL, |
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tick_nohz_cpu_down); |
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WARN_ON(ret < 0); |
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pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n", |
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cpumask_pr_args(tick_nohz_full_mask)); |
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} |
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#endif |
|
|
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/* |
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* NOHZ - aka dynamic tick functionality |
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*/ |
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#ifdef CONFIG_NO_HZ_COMMON |
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/* |
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* NO HZ enabled ? |
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*/ |
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bool tick_nohz_enabled __read_mostly = true; |
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unsigned long tick_nohz_active __read_mostly; |
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/* |
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* Enable / Disable tickless mode |
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*/ |
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static int __init setup_tick_nohz(char *str) |
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{ |
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return (kstrtobool(str, &tick_nohz_enabled) == 0); |
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} |
|
|
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__setup("nohz=", setup_tick_nohz); |
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|
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bool tick_nohz_tick_stopped(void) |
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{ |
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struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
|
|
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return ts->tick_stopped; |
|
} |
|
|
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bool tick_nohz_tick_stopped_cpu(int cpu) |
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{ |
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struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu); |
|
|
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return ts->tick_stopped; |
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} |
|
|
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/** |
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* tick_nohz_update_jiffies - update jiffies when idle was interrupted |
|
* |
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* Called from interrupt entry when the CPU was idle |
|
* |
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* 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 |
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* value. We do this unconditionally on any CPU, as we don't know whether the |
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* CPU, which has the update task assigned is in a long sleep. |
|
*/ |
|
static void tick_nohz_update_jiffies(ktime_t now) |
|
{ |
|
unsigned long flags; |
|
|
|
__this_cpu_write(tick_cpu_sched.idle_waketime, now); |
|
|
|
local_irq_save(flags); |
|
tick_do_update_jiffies64(now); |
|
local_irq_restore(flags); |
|
|
|
touch_softlockup_watchdog_sched(); |
|
} |
|
|
|
/* |
|
* Updates the per-CPU time idle statistics counters |
|
*/ |
|
static void |
|
update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time) |
|
{ |
|
ktime_t delta; |
|
|
|
if (ts->idle_active) { |
|
delta = ktime_sub(now, ts->idle_entrytime); |
|
if (nr_iowait_cpu(cpu) > 0) |
|
ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta); |
|
else |
|
ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); |
|
ts->idle_entrytime = now; |
|
} |
|
|
|
if (last_update_time) |
|
*last_update_time = ktime_to_us(now); |
|
|
|
} |
|
|
|
static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now) |
|
{ |
|
update_ts_time_stats(smp_processor_id(), ts, now, NULL); |
|
ts->idle_active = 0; |
|
|
|
sched_clock_idle_wakeup_event(); |
|
} |
|
|
|
static void tick_nohz_start_idle(struct tick_sched *ts) |
|
{ |
|
ts->idle_entrytime = ktime_get(); |
|
ts->idle_active = 1; |
|
sched_clock_idle_sleep_event(); |
|
} |
|
|
|
/** |
|
* get_cpu_idle_time_us - get the total idle time of a CPU |
|
* @cpu: CPU number to query |
|
* @last_update_time: variable to store update time in. Do not update |
|
* counters if NULL. |
|
* |
|
* Return the cumulative idle time (since boot) for a given |
|
* CPU, in microseconds. |
|
* |
|
* This time is measured via accounting rather than sampling, |
|
* and is as accurate as ktime_get() is. |
|
* |
|
* This function returns -1 if NOHZ is not enabled. |
|
*/ |
|
u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) |
|
{ |
|
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
|
ktime_t now, idle; |
|
|
|
if (!tick_nohz_active) |
|
return -1; |
|
|
|
now = ktime_get(); |
|
if (last_update_time) { |
|
update_ts_time_stats(cpu, ts, now, last_update_time); |
|
idle = ts->idle_sleeptime; |
|
} else { |
|
if (ts->idle_active && !nr_iowait_cpu(cpu)) { |
|
ktime_t delta = ktime_sub(now, ts->idle_entrytime); |
|
|
|
idle = ktime_add(ts->idle_sleeptime, delta); |
|
} else { |
|
idle = ts->idle_sleeptime; |
|
} |
|
} |
|
|
|
return ktime_to_us(idle); |
|
|
|
} |
|
EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); |
|
|
|
/** |
|
* get_cpu_iowait_time_us - get the total iowait time of a CPU |
|
* @cpu: CPU number to query |
|
* @last_update_time: variable to store update time in. Do not update |
|
* counters if NULL. |
|
* |
|
* Return the cumulative iowait time (since boot) for a given |
|
* CPU, in microseconds. |
|
* |
|
* This time is measured via accounting rather than sampling, |
|
* and is as accurate as ktime_get() is. |
|
* |
|
* This function returns -1 if NOHZ is not enabled. |
|
*/ |
|
u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time) |
|
{ |
|
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
|
ktime_t now, iowait; |
|
|
|
if (!tick_nohz_active) |
|
return -1; |
|
|
|
now = ktime_get(); |
|
if (last_update_time) { |
|
update_ts_time_stats(cpu, ts, now, last_update_time); |
|
iowait = ts->iowait_sleeptime; |
|
} else { |
|
if (ts->idle_active && nr_iowait_cpu(cpu) > 0) { |
|
ktime_t delta = ktime_sub(now, ts->idle_entrytime); |
|
|
|
iowait = ktime_add(ts->iowait_sleeptime, delta); |
|
} else { |
|
iowait = ts->iowait_sleeptime; |
|
} |
|
} |
|
|
|
return ktime_to_us(iowait); |
|
} |
|
EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us); |
|
|
|
static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) |
|
{ |
|
hrtimer_cancel(&ts->sched_timer); |
|
hrtimer_set_expires(&ts->sched_timer, ts->last_tick); |
|
|
|
/* Forward the time to expire in the future */ |
|
hrtimer_forward(&ts->sched_timer, now, TICK_NSEC); |
|
|
|
if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
|
hrtimer_start_expires(&ts->sched_timer, |
|
HRTIMER_MODE_ABS_PINNED_HARD); |
|
} else { |
|
tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1); |
|
} |
|
|
|
/* |
|
* Reset to make sure next tick stop doesn't get fooled by past |
|
* cached clock deadline. |
|
*/ |
|
ts->next_tick = 0; |
|
} |
|
|
|
static inline bool local_timer_softirq_pending(void) |
|
{ |
|
return local_softirq_pending() & BIT(TIMER_SOFTIRQ); |
|
} |
|
|
|
static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu) |
|
{ |
|
u64 basemono, next_tick, next_tmr, next_rcu, delta, expires; |
|
unsigned long basejiff; |
|
unsigned int seq; |
|
|
|
/* Read jiffies and the time when jiffies were updated last */ |
|
do { |
|
seq = read_seqcount_begin(&jiffies_seq); |
|
basemono = last_jiffies_update; |
|
basejiff = jiffies; |
|
} while (read_seqcount_retry(&jiffies_seq, seq)); |
|
ts->last_jiffies = basejiff; |
|
ts->timer_expires_base = basemono; |
|
|
|
/* |
|
* Keep the periodic tick, when RCU, architecture or irq_work |
|
* requests it. |
|
* Aside of that check whether the local timer softirq is |
|
* pending. If so its a bad idea to call get_next_timer_interrupt() |
|
* because there is an already expired timer, so it will request |
|
* immeditate expiry, which rearms the hardware timer with a |
|
* minimal delta which brings us back to this place |
|
* immediately. Lather, rinse and repeat... |
|
*/ |
|
if (rcu_needs_cpu(basemono, &next_rcu) || arch_needs_cpu() || |
|
irq_work_needs_cpu() || local_timer_softirq_pending()) { |
|
next_tick = basemono + TICK_NSEC; |
|
} else { |
|
/* |
|
* Get the next pending timer. If high resolution |
|
* timers are enabled this only takes the timer wheel |
|
* timers into account. If high resolution timers are |
|
* disabled this also looks at the next expiring |
|
* hrtimer. |
|
*/ |
|
next_tmr = get_next_timer_interrupt(basejiff, basemono); |
|
ts->next_timer = next_tmr; |
|
/* Take the next rcu event into account */ |
|
next_tick = next_rcu < next_tmr ? next_rcu : next_tmr; |
|
} |
|
|
|
/* |
|
* If the tick is due in the next period, keep it ticking or |
|
* force prod the timer. |
|
*/ |
|
delta = next_tick - basemono; |
|
if (delta <= (u64)TICK_NSEC) { |
|
/* |
|
* Tell the timer code that the base is not idle, i.e. undo |
|
* the effect of get_next_timer_interrupt(): |
|
*/ |
|
timer_clear_idle(); |
|
/* |
|
* We've not stopped the tick yet, and there's a timer in the |
|
* next period, so no point in stopping it either, bail. |
|
*/ |
|
if (!ts->tick_stopped) { |
|
ts->timer_expires = 0; |
|
goto out; |
|
} |
|
} |
|
|
|
/* |
|
* If this CPU is the one which had the do_timer() duty last, we limit |
|
* the sleep time to the timekeeping max_deferment value. |
|
* Otherwise we can sleep as long as we want. |
|
*/ |
|
delta = timekeeping_max_deferment(); |
|
if (cpu != tick_do_timer_cpu && |
|
(tick_do_timer_cpu != TICK_DO_TIMER_NONE || !ts->do_timer_last)) |
|
delta = KTIME_MAX; |
|
|
|
/* Calculate the next expiry time */ |
|
if (delta < (KTIME_MAX - basemono)) |
|
expires = basemono + delta; |
|
else |
|
expires = KTIME_MAX; |
|
|
|
ts->timer_expires = min_t(u64, expires, next_tick); |
|
|
|
out: |
|
return ts->timer_expires; |
|
} |
|
|
|
static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu) |
|
{ |
|
struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); |
|
u64 basemono = ts->timer_expires_base; |
|
u64 expires = ts->timer_expires; |
|
ktime_t tick = expires; |
|
|
|
/* Make sure we won't be trying to stop it twice in a row. */ |
|
ts->timer_expires_base = 0; |
|
|
|
/* |
|
* If this CPU is the one which updates jiffies, then give up |
|
* the assignment and let it be taken by the CPU which runs |
|
* the tick timer next, which might be this CPU as well. If we |
|
* don't drop this here the jiffies might be stale and |
|
* do_timer() never invoked. Keep track of the fact that it |
|
* was the one which had the do_timer() duty last. |
|
*/ |
|
if (cpu == tick_do_timer_cpu) { |
|
tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
|
ts->do_timer_last = 1; |
|
} else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) { |
|
ts->do_timer_last = 0; |
|
} |
|
|
|
/* Skip reprogram of event if its not changed */ |
|
if (ts->tick_stopped && (expires == ts->next_tick)) { |
|
/* Sanity check: make sure clockevent is actually programmed */ |
|
if (tick == KTIME_MAX || ts->next_tick == hrtimer_get_expires(&ts->sched_timer)) |
|
return; |
|
|
|
WARN_ON_ONCE(1); |
|
printk_once("basemono: %llu ts->next_tick: %llu dev->next_event: %llu timer->active: %d timer->expires: %llu\n", |
|
basemono, ts->next_tick, dev->next_event, |
|
hrtimer_active(&ts->sched_timer), hrtimer_get_expires(&ts->sched_timer)); |
|
} |
|
|
|
/* |
|
* 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) { |
|
calc_load_nohz_start(); |
|
quiet_vmstat(); |
|
|
|
ts->last_tick = hrtimer_get_expires(&ts->sched_timer); |
|
ts->tick_stopped = 1; |
|
trace_tick_stop(1, TICK_DEP_MASK_NONE); |
|
} |
|
|
|
ts->next_tick = tick; |
|
|
|
/* |
|
* If the expiration time == KTIME_MAX, then we simply stop |
|
* the tick timer. |
|
*/ |
|
if (unlikely(expires == KTIME_MAX)) { |
|
if (ts->nohz_mode == NOHZ_MODE_HIGHRES) |
|
hrtimer_cancel(&ts->sched_timer); |
|
return; |
|
} |
|
|
|
if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
|
hrtimer_start(&ts->sched_timer, tick, |
|
HRTIMER_MODE_ABS_PINNED_HARD); |
|
} else { |
|
hrtimer_set_expires(&ts->sched_timer, tick); |
|
tick_program_event(tick, 1); |
|
} |
|
} |
|
|
|
static void tick_nohz_retain_tick(struct tick_sched *ts) |
|
{ |
|
ts->timer_expires_base = 0; |
|
} |
|
|
|
#ifdef CONFIG_NO_HZ_FULL |
|
static void tick_nohz_stop_sched_tick(struct tick_sched *ts, int cpu) |
|
{ |
|
if (tick_nohz_next_event(ts, cpu)) |
|
tick_nohz_stop_tick(ts, cpu); |
|
else |
|
tick_nohz_retain_tick(ts); |
|
} |
|
#endif /* CONFIG_NO_HZ_FULL */ |
|
|
|
static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now) |
|
{ |
|
/* Update jiffies first */ |
|
tick_do_update_jiffies64(now); |
|
|
|
/* |
|
* Clear the timer idle flag, so we avoid IPIs on remote queueing and |
|
* the clock forward checks in the enqueue path: |
|
*/ |
|
timer_clear_idle(); |
|
|
|
calc_load_nohz_stop(); |
|
touch_softlockup_watchdog_sched(); |
|
/* |
|
* Cancel the scheduled timer and restore the tick |
|
*/ |
|
ts->tick_stopped = 0; |
|
ts->idle_exittime = now; |
|
|
|
tick_nohz_restart(ts, now); |
|
} |
|
|
|
static void tick_nohz_full_update_tick(struct tick_sched *ts) |
|
{ |
|
#ifdef CONFIG_NO_HZ_FULL |
|
int cpu = smp_processor_id(); |
|
|
|
if (!tick_nohz_full_cpu(cpu)) |
|
return; |
|
|
|
if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) |
|
return; |
|
|
|
if (can_stop_full_tick(cpu, ts)) |
|
tick_nohz_stop_sched_tick(ts, cpu); |
|
else if (ts->tick_stopped) |
|
tick_nohz_restart_sched_tick(ts, ktime_get()); |
|
#endif |
|
} |
|
|
|
static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) |
|
{ |
|
/* |
|
* If this CPU is offline and it is the one which updates |
|
* jiffies, then give up the assignment and let it be taken by |
|
* the CPU which runs the tick timer next. If we don't drop |
|
* this here the jiffies might be stale and do_timer() never |
|
* invoked. |
|
*/ |
|
if (unlikely(!cpu_online(cpu))) { |
|
if (cpu == tick_do_timer_cpu) |
|
tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
|
/* |
|
* Make sure the CPU doesn't get fooled by obsolete tick |
|
* deadline if it comes back online later. |
|
*/ |
|
ts->next_tick = 0; |
|
return false; |
|
} |
|
|
|
if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) |
|
return false; |
|
|
|
if (need_resched()) |
|
return false; |
|
|
|
if (unlikely(local_softirq_pending())) { |
|
static int ratelimit; |
|
|
|
if (ratelimit < 10 && |
|
(local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { |
|
pr_warn("NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #%02x!!!\n", |
|
(unsigned int) local_softirq_pending()); |
|
ratelimit++; |
|
} |
|
return false; |
|
} |
|
|
|
if (tick_nohz_full_enabled()) { |
|
/* |
|
* Keep the tick alive to guarantee timekeeping progression |
|
* if there are full dynticks CPUs around |
|
*/ |
|
if (tick_do_timer_cpu == cpu) |
|
return false; |
|
|
|
/* Should not happen for nohz-full */ |
|
if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
|
return false; |
|
} |
|
|
|
return true; |
|
} |
|
|
|
static void __tick_nohz_idle_stop_tick(struct tick_sched *ts) |
|
{ |
|
ktime_t expires; |
|
int cpu = smp_processor_id(); |
|
|
|
/* |
|
* If tick_nohz_get_sleep_length() ran tick_nohz_next_event(), the |
|
* tick timer expiration time is known already. |
|
*/ |
|
if (ts->timer_expires_base) |
|
expires = ts->timer_expires; |
|
else if (can_stop_idle_tick(cpu, ts)) |
|
expires = tick_nohz_next_event(ts, cpu); |
|
else |
|
return; |
|
|
|
ts->idle_calls++; |
|
|
|
if (expires > 0LL) { |
|
int was_stopped = ts->tick_stopped; |
|
|
|
tick_nohz_stop_tick(ts, cpu); |
|
|
|
ts->idle_sleeps++; |
|
ts->idle_expires = expires; |
|
|
|
if (!was_stopped && ts->tick_stopped) { |
|
ts->idle_jiffies = ts->last_jiffies; |
|
nohz_balance_enter_idle(cpu); |
|
} |
|
} else { |
|
tick_nohz_retain_tick(ts); |
|
} |
|
} |
|
|
|
/** |
|
* tick_nohz_idle_stop_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 |
|
*/ |
|
void tick_nohz_idle_stop_tick(void) |
|
{ |
|
__tick_nohz_idle_stop_tick(this_cpu_ptr(&tick_cpu_sched)); |
|
} |
|
|
|
void tick_nohz_idle_retain_tick(void) |
|
{ |
|
tick_nohz_retain_tick(this_cpu_ptr(&tick_cpu_sched)); |
|
/* |
|
* Undo the effect of get_next_timer_interrupt() called from |
|
* tick_nohz_next_event(). |
|
*/ |
|
timer_clear_idle(); |
|
} |
|
|
|
/** |
|
* tick_nohz_idle_enter - prepare for entering idle on the current CPU |
|
* |
|
* Called when we start the idle loop. |
|
*/ |
|
void tick_nohz_idle_enter(void) |
|
{ |
|
struct tick_sched *ts; |
|
|
|
lockdep_assert_irqs_enabled(); |
|
|
|
local_irq_disable(); |
|
|
|
ts = this_cpu_ptr(&tick_cpu_sched); |
|
|
|
WARN_ON_ONCE(ts->timer_expires_base); |
|
|
|
ts->inidle = 1; |
|
tick_nohz_start_idle(ts); |
|
|
|
local_irq_enable(); |
|
} |
|
|
|
/** |
|
* tick_nohz_irq_exit - update next tick event from interrupt exit |
|
* |
|
* When an interrupt fires while we are idle and it doesn't cause |
|
* a reschedule, it may still add, modify or delete a timer, enqueue |
|
* an RCU callback, etc... |
|
* So we need to re-calculate and reprogram the next tick event. |
|
*/ |
|
void tick_nohz_irq_exit(void) |
|
{ |
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
|
|
|
if (ts->inidle) |
|
tick_nohz_start_idle(ts); |
|
else |
|
tick_nohz_full_update_tick(ts); |
|
} |
|
|
|
/** |
|
* tick_nohz_idle_got_tick - Check whether or not the tick handler has run |
|
*/ |
|
bool tick_nohz_idle_got_tick(void) |
|
{ |
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
|
|
|
if (ts->got_idle_tick) { |
|
ts->got_idle_tick = 0; |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
/** |
|
* tick_nohz_get_next_hrtimer - return the next expiration time for the hrtimer |
|
* or the tick, whatever that expires first. Note that, if the tick has been |
|
* stopped, it returns the next hrtimer. |
|
* |
|
* Called from power state control code with interrupts disabled |
|
*/ |
|
ktime_t tick_nohz_get_next_hrtimer(void) |
|
{ |
|
return __this_cpu_read(tick_cpu_device.evtdev)->next_event; |
|
} |
|
|
|
/** |
|
* tick_nohz_get_sleep_length - return the expected length of the current sleep |
|
* @delta_next: duration until the next event if the tick cannot be stopped |
|
* |
|
* Called from power state control code with interrupts disabled |
|
*/ |
|
ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next) |
|
{ |
|
struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); |
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
|
int cpu = smp_processor_id(); |
|
/* |
|
* The idle entry time is expected to be a sufficient approximation of |
|
* the current time at this point. |
|
*/ |
|
ktime_t now = ts->idle_entrytime; |
|
ktime_t next_event; |
|
|
|
WARN_ON_ONCE(!ts->inidle); |
|
|
|
*delta_next = ktime_sub(dev->next_event, now); |
|
|
|
if (!can_stop_idle_tick(cpu, ts)) |
|
return *delta_next; |
|
|
|
next_event = tick_nohz_next_event(ts, cpu); |
|
if (!next_event) |
|
return *delta_next; |
|
|
|
/* |
|
* If the next highres timer to expire is earlier than next_event, the |
|
* idle governor needs to know that. |
|
*/ |
|
next_event = min_t(u64, next_event, |
|
hrtimer_next_event_without(&ts->sched_timer)); |
|
|
|
return ktime_sub(next_event, now); |
|
} |
|
|
|
/** |
|
* tick_nohz_get_idle_calls_cpu - return the current idle calls counter value |
|
* for a particular CPU. |
|
* |
|
* Called from the schedutil frequency scaling governor in scheduler context. |
|
*/ |
|
unsigned long tick_nohz_get_idle_calls_cpu(int cpu) |
|
{ |
|
struct tick_sched *ts = tick_get_tick_sched(cpu); |
|
|
|
return ts->idle_calls; |
|
} |
|
|
|
/** |
|
* tick_nohz_get_idle_calls - return the current idle calls counter value |
|
* |
|
* Called from the schedutil frequency scaling governor in scheduler context. |
|
*/ |
|
unsigned long tick_nohz_get_idle_calls(void) |
|
{ |
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
|
|
|
return ts->idle_calls; |
|
} |
|
|
|
static void tick_nohz_account_idle_ticks(struct tick_sched *ts) |
|
{ |
|
#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE |
|
unsigned long ticks; |
|
|
|
if (vtime_accounting_enabled_this_cpu()) |
|
return; |
|
/* |
|
* 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) |
|
account_idle_ticks(ticks); |
|
#endif |
|
} |
|
|
|
static void __tick_nohz_idle_restart_tick(struct tick_sched *ts, ktime_t now) |
|
{ |
|
tick_nohz_restart_sched_tick(ts, now); |
|
tick_nohz_account_idle_ticks(ts); |
|
} |
|
|
|
void tick_nohz_idle_restart_tick(void) |
|
{ |
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
|
|
|
if (ts->tick_stopped) |
|
__tick_nohz_idle_restart_tick(ts, ktime_get()); |
|
} |
|
|
|
/** |
|
* tick_nohz_idle_exit - restart the idle tick from the idle task |
|
* |
|
* Restart the idle tick when the CPU is woken up from idle |
|
* This also exit the RCU extended quiescent state. The CPU |
|
* can use RCU again after this function is called. |
|
*/ |
|
void tick_nohz_idle_exit(void) |
|
{ |
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
|
bool idle_active, tick_stopped; |
|
ktime_t now; |
|
|
|
local_irq_disable(); |
|
|
|
WARN_ON_ONCE(!ts->inidle); |
|
WARN_ON_ONCE(ts->timer_expires_base); |
|
|
|
ts->inidle = 0; |
|
idle_active = ts->idle_active; |
|
tick_stopped = ts->tick_stopped; |
|
|
|
if (idle_active || tick_stopped) |
|
now = ktime_get(); |
|
|
|
if (idle_active) |
|
tick_nohz_stop_idle(ts, now); |
|
|
|
if (tick_stopped) |
|
__tick_nohz_idle_restart_tick(ts, now); |
|
|
|
local_irq_enable(); |
|
} |
|
|
|
/* |
|
* The nohz low res interrupt handler |
|
*/ |
|
static void tick_nohz_handler(struct clock_event_device *dev) |
|
{ |
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
|
struct pt_regs *regs = get_irq_regs(); |
|
ktime_t now = ktime_get(); |
|
|
|
dev->next_event = KTIME_MAX; |
|
|
|
tick_sched_do_timer(ts, now); |
|
tick_sched_handle(ts, regs); |
|
|
|
/* No need to reprogram if we are running tickless */ |
|
if (unlikely(ts->tick_stopped)) |
|
return; |
|
|
|
hrtimer_forward(&ts->sched_timer, now, TICK_NSEC); |
|
tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1); |
|
} |
|
|
|
static inline void tick_nohz_activate(struct tick_sched *ts, int mode) |
|
{ |
|
if (!tick_nohz_enabled) |
|
return; |
|
ts->nohz_mode = mode; |
|
/* One update is enough */ |
|
if (!test_and_set_bit(0, &tick_nohz_active)) |
|
timers_update_nohz(); |
|
} |
|
|
|
/** |
|
* tick_nohz_switch_to_nohz - switch to nohz mode |
|
*/ |
|
static void tick_nohz_switch_to_nohz(void) |
|
{ |
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
|
ktime_t next; |
|
|
|
if (!tick_nohz_enabled) |
|
return; |
|
|
|
if (tick_switch_to_oneshot(tick_nohz_handler)) |
|
return; |
|
|
|
/* |
|
* 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_HARD); |
|
/* Get the next period */ |
|
next = tick_init_jiffy_update(); |
|
|
|
hrtimer_set_expires(&ts->sched_timer, next); |
|
hrtimer_forward_now(&ts->sched_timer, TICK_NSEC); |
|
tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1); |
|
tick_nohz_activate(ts, NOHZ_MODE_LOWRES); |
|
} |
|
|
|
static inline void tick_nohz_irq_enter(void) |
|
{ |
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
|
ktime_t now; |
|
|
|
if (!ts->idle_active && !ts->tick_stopped) |
|
return; |
|
now = ktime_get(); |
|
if (ts->idle_active) |
|
tick_nohz_stop_idle(ts, now); |
|
if (ts->tick_stopped) |
|
tick_nohz_update_jiffies(now); |
|
} |
|
|
|
#else |
|
|
|
static inline void tick_nohz_switch_to_nohz(void) { } |
|
static inline void tick_nohz_irq_enter(void) { } |
|
static inline void tick_nohz_activate(struct tick_sched *ts, int mode) { } |
|
|
|
#endif /* CONFIG_NO_HZ_COMMON */ |
|
|
|
/* |
|
* Called from irq_enter to notify about the possible interruption of idle() |
|
*/ |
|
void tick_irq_enter(void) |
|
{ |
|
tick_check_oneshot_broadcast_this_cpu(); |
|
tick_nohz_irq_enter(); |
|
} |
|
|
|
/* |
|
* 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. |
|
*/ |
|
static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) |
|
{ |
|
struct tick_sched *ts = |
|
container_of(timer, struct tick_sched, sched_timer); |
|
struct pt_regs *regs = get_irq_regs(); |
|
ktime_t now = ktime_get(); |
|
|
|
tick_sched_do_timer(ts, now); |
|
|
|
/* |
|
* Do not call, when we are not in irq context and have |
|
* no valid regs pointer |
|
*/ |
|
if (regs) |
|
tick_sched_handle(ts, regs); |
|
else |
|
ts->next_tick = 0; |
|
|
|
/* No need to reprogram if we are in idle or full dynticks mode */ |
|
if (unlikely(ts->tick_stopped)) |
|
return HRTIMER_NORESTART; |
|
|
|
hrtimer_forward(timer, now, TICK_NSEC); |
|
|
|
return HRTIMER_RESTART; |
|
} |
|
|
|
static int sched_skew_tick; |
|
|
|
static int __init skew_tick(char *str) |
|
{ |
|
get_option(&str, &sched_skew_tick); |
|
|
|
return 0; |
|
} |
|
early_param("skew_tick", skew_tick); |
|
|
|
/** |
|
* tick_setup_sched_timer - setup the tick emulation timer |
|
*/ |
|
void tick_setup_sched_timer(void) |
|
{ |
|
struct tick_sched *ts = this_cpu_ptr(&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_HARD); |
|
ts->sched_timer.function = tick_sched_timer; |
|
|
|
/* Get the next period (per-CPU) */ |
|
hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update()); |
|
|
|
/* Offset the tick to avert jiffies_lock contention. */ |
|
if (sched_skew_tick) { |
|
u64 offset = TICK_NSEC >> 1; |
|
do_div(offset, num_possible_cpus()); |
|
offset *= smp_processor_id(); |
|
hrtimer_add_expires_ns(&ts->sched_timer, offset); |
|
} |
|
|
|
hrtimer_forward(&ts->sched_timer, now, TICK_NSEC); |
|
hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD); |
|
tick_nohz_activate(ts, NOHZ_MODE_HIGHRES); |
|
} |
|
#endif /* HIGH_RES_TIMERS */ |
|
|
|
#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS |
|
void tick_cancel_sched_timer(int cpu) |
|
{ |
|
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
|
|
|
# ifdef CONFIG_HIGH_RES_TIMERS |
|
if (ts->sched_timer.base) |
|
hrtimer_cancel(&ts->sched_timer); |
|
# endif |
|
|
|
memset(ts, 0, sizeof(*ts)); |
|
} |
|
#endif |
|
|
|
/** |
|
* 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 = this_cpu_ptr(&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). Called with interrupts disabled. |
|
*/ |
|
int tick_check_oneshot_change(int allow_nohz) |
|
{ |
|
struct tick_sched *ts = this_cpu_ptr(&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_valid_for_hres() || !tick_is_oneshot_available()) |
|
return 0; |
|
|
|
if (!allow_nohz) |
|
return 1; |
|
|
|
tick_nohz_switch_to_nohz(); |
|
return 0; |
|
}
|
|
|