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Commit 99d5f3aa authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

timers: Add accounting of non deferrable timers 



The code in get_next_timer_interrupt() is suboptimal as it has to run
through the cascade to find the next expiring timer. On a completely
idle core we should only do that when there is an active timer
enqueued and base->next_timer does not give us a fast answer.

Add accounting of the active timers to the now consolidated
attach/detach code. I deliberately avoided sanity checks because the
code is fully symetric and any fiddling with timers w/o using the API
functions will lead to cute explosions anyway. ulong is big enough
even on 32bit and if we really run into the situation to have more
than 1<<32 timers enqueued there, then we are definitely not in a
state to go idle and run through that code.

This allows us to fix another shortcoming of get_next_timer_interrupt().

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20120525214819.236377028@linutronix.de
parent facbb4a7

kernel/timer.c

+23 −8
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ struct tvec_base { 
	struct timer_list *running_timer;

	unsigned long timer_jiffies;

	unsigned long next_timer;

	unsigned long active_timers;

	struct tvec_root tv1;

	struct tvec tv2;

	struct tvec tv3;
@@ -377,11 +378,13 @@ static void internal_add_timer(struct tvec_base *base, struct timer_list *timer) 
{

	__internal_add_timer(base, timer);

	/*

	 * Update base->next_timer if this is the earliest one.

	 * Update base->active_timers and base->next_timer

	 */

	if (time_before(timer->expires, base->next_timer) &&

	    !tbase_get_deferrable(timer->base))

	if (!tbase_get_deferrable(timer->base)) {

		if (time_before(timer->expires, base->next_timer))

			base->next_timer = timer->expires;

		base->active_timers++;

	}

}



#ifdef CONFIG_TIMER_STATS
@@ -678,6 +681,14 @@ static inline void detach_timer(struct timer_list *timer, bool clear_pending) 
	entry->prev = LIST_POISON2;

}



static inline void

detach_expired_timer(struct timer_list *timer, struct tvec_base *base)

{

	detach_timer(timer, true);

	if (!tbase_get_deferrable(timer->base))

		timer->base->active_timers--;

}



static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,

			     bool clear_pending)

{
@@ -685,9 +696,11 @@ static int detach_if_pending(struct timer_list *timer, struct tvec_base *base, 
		return 0;



	detach_timer(timer, clear_pending);

	if (timer->expires == base->next_timer &&

	    !tbase_get_deferrable(timer->base))

	if (!tbase_get_deferrable(timer->base)) {

		timer->base->active_timers--;

		if (timer->expires == base->next_timer)

			base->next_timer = base->timer_jiffies;

	}

	return 1;

}
@@ -1175,7 +1188,7 @@ static inline void __run_timers(struct tvec_base *base) 
			timer_stats_account_timer(timer);



			base->running_timer = timer;

			detach_timer(timer, true);

			detach_expired_timer(timer, base);



			spin_unlock_irq(&base->lock);

			call_timer_fn(timer, fn, data);
@@ -1701,6 +1714,7 @@ static int __cpuinit init_timers_cpu(int cpu) 


	base->timer_jiffies = jiffies;

	base->next_timer = base->timer_jiffies;

	base->active_timers = 0;

	return 0;

}
@@ -1711,6 +1725,7 @@ static void migrate_timer_list(struct tvec_base *new_base, struct list_head *hea 


	while (!list_empty(head)) {

		timer = list_first_entry(head, struct timer_list, entry);

		/* We ignore the accounting on the dying cpu */

		detach_timer(timer, false);

		timer_set_base(timer, new_base);

		internal_add_timer(new_base, timer);