自学教程：C++ tick_nohz_restart函数代码示例

/** * 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){	int cpu = smp_processor_id();	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);#ifndef CONFIG_VIRT_CPU_ACCOUNTING	unsigned long ticks;#endif	ktime_t now;	local_irq_disable();	WARN_ON_ONCE(!ts->inidle);	ts->inidle = 0;	if (ts->idle_active || ts->tick_stopped)		now = ktime_get();	if (ts->idle_active)		tick_nohz_stop_idle(cpu, now);	if (!ts->tick_stopped) {		local_irq_enable();		return;	}	/* Update jiffies first */	select_nohz_load_balancer(0);	tick_do_update_jiffies64(now);#ifdef CONFIG_MTK_SCHED_CMP	update_cpu_load_nohz();#endif#ifndef CONFIG_VIRT_CPU_ACCOUNTING	/*	 * 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	calc_load_exit_idle();	touch_softlockup_watchdog();	/*	 * Cancel the scheduled timer and restore the tick	 */	ts->tick_stopped  = 0;	ts->idle_exittime = now;	tick_nohz_restart(ts, now);	local_irq_enable();}

static void tick_nohz_kick_tick(int cpu, ktime_t now){#if 0		struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);	ktime_t delta;	delta =	ktime_sub(hrtimer_get_expires(&ts->sched_timer), now);	if (delta.tv64 <= tick_period.tv64)		return;	tick_nohz_restart(ts, now);#endif}

/* * 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, ktime_t now){#if 0	/* Switch back to 2.6.27 behaviour */	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);	ktime_t delta;	/*	 * Do not touch the tick device, when the next expiry is either	 * already reached or less/equal than the tick period.	 */	delta =	ktime_sub(hrtimer_get_expires(&ts->sched_timer), now);	if (delta.tv64 <= tick_period.tv64)		return;	tick_nohz_restart(ts, now);#endif}

void tick_nohz_restart_sched_tick(void)#endif{	int cpu = smp_processor_id();	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);#ifndef CONFIG_VIRT_CPU_ACCOUNTING	unsigned long ticks;#endif	ktime_t now;	local_irq_disable();	if (ts->idle_active || (ts->inidle && ts->tick_stopped))		now = ktime_get();	if (ts->idle_active)		tick_nohz_stop_idle(cpu, now);	if (!ts->inidle || !ts->tick_stopped) {		ts->inidle = 0;#ifdef CONFIG_DATAPLANE		if (!user_idle)#endif		local_irq_enable();		return;	}	ts->inidle = 0;	rcu_exit_nohz();	/* Update jiffies first */	select_nohz_load_balancer(0);	tick_do_update_jiffies64(now);	cpumask_clear_cpu(cpu, nohz_cpu_mask);#ifndef CONFIG_VIRT_CPU_ACCOUNTING	/*	 * 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)#ifdef CONFIG_DATAPLANE	{		if (user_idle) {			cputime_t cpu_time = jiffies_to_cputime(ticks);			account_user_time(current, cpu_time,					  cputime_to_scaled(cpu_time));		} else {			account_idle_ticks(ticks);		}	}#else		account_idle_ticks(ticks);#endif#endif	touch_softlockup_watchdog();	/*	 * Cancel the scheduled timer and restore the tick	 */	ts->tick_stopped  = 0;	ts->idle_exittime = now;	tick_nohz_restart(ts, now);#ifdef CONFIG_DATAPLANE	if (!user_idle)#endif	local_irq_enable();}