Commit dc2a0f1f authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Thomas Gleixner
Browse files

timers: Always keep track of next expiry 



So far next expiry was only tracked while the CPU was in nohz_idle mode
in order to cope with missing ticks that can't increment the base->clk
periodically anymore.

This logic is going to be expanded beyond nohz in order to spare timer
softirqs so do it unconditionally.

Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarJuri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-8-frederic@kernel.org
parent 001ec1b3

kernel/time/timer.c

+21 −21
Original line number Diff line number Diff line
@@ -544,8 +544,7 @@ static int calc_wheel_index(unsigned long expires, unsigned long clk, 
}



static void

trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer,

		    unsigned long bucket_expiry)

trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)

{

	if (!is_timers_nohz_active())

		return;
@@ -565,22 +564,7 @@ trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer, 
	 * timer is not deferrable. If the other CPU is on the way to idle

	 * then it can't set base->is_idle as we hold the base lock:

	 */

	if (!base->is_idle)

		return;



	/*

	 * Check whether this is the new first expiring timer. The

	 * effective expiry time of the timer is required here

	 * (bucket_expiry) instead of timer->expires.

	 */

	if (time_after_eq(bucket_expiry, base->next_expiry))

		return;



	/*

	 * Set the next expiry time and kick the CPU so it can reevaluate the

	 * wheel:

	 */

	base->next_expiry = bucket_expiry;

	if (base->is_idle)

		wake_up_nohz_cpu(base->cpu);

}
@@ -592,12 +576,26 @@ trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer, 
static void enqueue_timer(struct timer_base *base, struct timer_list *timer,

			  unsigned int idx, unsigned long bucket_expiry)

{



	hlist_add_head(&timer->entry, base->vectors + idx);

	__set_bit(idx, base->pending_map);

	timer_set_idx(timer, idx);



	trace_timer_start(timer, timer->expires, timer->flags);

	trigger_dyntick_cpu(base, timer, bucket_expiry);



	/*

	 * Check whether this is the new first expiring timer. The

	 * effective expiry time of the timer is required here

	 * (bucket_expiry) instead of timer->expires.

	 */

	if (time_before(bucket_expiry, base->next_expiry)) {

		/*

		 * Set the next expiry time and kick the CPU so it

		 * can reevaluate the wheel:

		 */

		base->next_expiry = bucket_expiry;

		trigger_dyntick_cpu(base, timer);

	}

}



static void internal_add_timer(struct timer_base *base, struct timer_list *timer)
@@ -1493,7 +1491,6 @@ static int __collect_expired_timers(struct timer_base *base, 
	return levels;

}



#ifdef CONFIG_NO_HZ_COMMON

/*

 * Find the next pending bucket of a level. Search from level start (@offset)

 * + @clk upwards and if nothing there, search from start of the level
@@ -1585,6 +1582,7 @@ static unsigned long __next_timer_interrupt(struct timer_base *base) 
	return next;

}



#ifdef CONFIG_NO_HZ_COMMON

/*

 * Check, if the next hrtimer event is before the next timer wheel

 * event:
@@ -1790,6 +1788,7 @@ static inline void __run_timers(struct timer_base *base) 


		levels = collect_expired_timers(base, heads);

		base->clk++;

		base->next_expiry = __next_timer_interrupt(base);



		while (levels--)

			expire_timers(base, heads + levels);
@@ -2042,6 +2041,7 @@ static void __init init_timer_cpu(int cpu) 
		base->cpu = cpu;

		raw_spin_lock_init(&base->lock);

		base->clk = jiffies;

		base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;

		timer_base_init_expiry_lock(base);

	}

}