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Commit 74019224 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

timers: add mod_timer_pending() 



Impact: new timer API

Based on an idea from Martin Josefsson with the help of
Patrick McHardy and Stephen Hemminger:

introduce the mod_timer_pending() API which is a mod_timer()
offspring that is an invariant on already removed timers.

(regular mod_timer() re-activates non-pending timers.)

This is useful for the networking code in that it can
allow unserialized mod_timer_pending() timer-forwarding
calls, but a single del_timer*() will stop the timer
from being reactivated again.

Also while at it:

- optimize the regular mod_timer() path some more, the
  timer-stat and a debug check was needlessly duplicated
  in __mod_timer().

- make the exports come straight after the function, as
  most other exports in timer.c already did.

- eliminate __mod_timer() as an external API, change the
  users to mod_timer().

The regular mod_timer() code path is not impacted
significantly, due to inlining optimizations and due to
the simplifications.

Based-on-patch-from: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: default avatarStephen Hemminger <shemminger@vyatta.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Patrick McHardy <kaber@trash.net>
Cc: netdev@vger.kernel.org
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 5955c7a2

arch/powerpc/platforms/cell/spufs/sched.c

+1 −1
Original line number Diff line number Diff line
@@ -508,7 +508,7 @@ static void __spu_add_to_rq(struct spu_context *ctx) 
		list_add_tail(&ctx->rq, &spu_prio->runq[ctx->prio]);

		set_bit(ctx->prio, spu_prio->bitmap);

		if (!spu_prio->nr_waiting++)

			__mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);

			mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);

	}

}

drivers/infiniband/hw/ipath/ipath_driver.c

+3 −3
Original line number Diff line number Diff line
@@ -2715,7 +2715,7 @@ static void ipath_hol_signal_up(struct ipath_devdata *dd) 
 * to prevent HoL blocking, then start the HoL timer that

 * periodically continues, then stop procs, so they can detect

 * link down if they want, and do something about it.

 * Timer may already be running, so use __mod_timer, not add_timer.

 * Timer may already be running, so use mod_timer, not add_timer.

 */

void ipath_hol_down(struct ipath_devdata *dd)

{
@@ -2724,7 +2724,7 @@ void ipath_hol_down(struct ipath_devdata *dd) 
	dd->ipath_hol_next = IPATH_HOL_DOWNCONT;

	dd->ipath_hol_timer.expires = jiffies +

		msecs_to_jiffies(ipath_hol_timeout_ms);

	__mod_timer(&dd->ipath_hol_timer, dd->ipath_hol_timer.expires);

	mod_timer(&dd->ipath_hol_timer, dd->ipath_hol_timer.expires);

}



/*
@@ -2763,7 +2763,7 @@ void ipath_hol_event(unsigned long opaque) 
	else {

		dd->ipath_hol_timer.expires = jiffies +

			msecs_to_jiffies(ipath_hol_timeout_ms);

		__mod_timer(&dd->ipath_hol_timer,

		mod_timer(&dd->ipath_hol_timer,

			dd->ipath_hol_timer.expires);

	}

}

include/linux/timer.h

+2 −20
Original line number Diff line number Diff line
@@ -86,8 +86,8 @@ static inline int timer_pending(const struct timer_list * timer) 


extern void add_timer_on(struct timer_list *timer, int cpu);

extern int del_timer(struct timer_list * timer);

extern int __mod_timer(struct timer_list *timer, unsigned long expires);

extern int mod_timer(struct timer_list *timer, unsigned long expires);

extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);



/*

 * The jiffies value which is added to now, when there is no timer
@@ -146,25 +146,7 @@ static inline void timer_stats_timer_clear_start_info(struct timer_list *timer) 
}

#endif



/**

 * add_timer - start a timer

 * @timer: the timer to be added

 *

 * The kernel will do a ->function(->data) callback from the

 * timer interrupt at the ->expires point in the future. The

 * current time is 'jiffies'.

 *

 * The timer's ->expires, ->function (and if the handler uses it, ->data)

 * fields must be set prior calling this function.

 *

 * Timers with an ->expires field in the past will be executed in the next

 * timer tick.

 */

static inline void add_timer(struct timer_list *timer)

{

	BUG_ON(timer_pending(timer));

	__mod_timer(timer, timer->expires);

}

extern void add_timer(struct timer_list *timer);



#ifdef CONFIG_SMP

  extern int try_to_del_timer_sync(struct timer_list *timer);

kernel/relay.c

+1 −1
Original line number Diff line number Diff line
@@ -750,7 +750,7 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length) 
			 * from the scheduler (trying to re-grab

			 * rq->lock), so defer it.

			 */

			__mod_timer(&buf->timer, jiffies + 1);

			mod_timer(&buf->timer, jiffies + 1);

	}



	old = buf->data;

kernel/timer.c

+73 −37
Original line number Diff line number Diff line
@@ -589,11 +589,14 @@ static struct tvec_base *lock_timer_base(struct timer_list *timer, 
	}

}



int __mod_timer(struct timer_list *timer, unsigned long expires)

static inline int

__mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)

{

	struct tvec_base *base, *new_base;

	unsigned long flags;

	int ret = 0;

	int ret;



	ret = 0;



	timer_stats_timer_set_start_info(timer);

	BUG_ON(!timer->function);
@@ -603,6 +606,9 @@ int __mod_timer(struct timer_list *timer, unsigned long expires) 
	if (timer_pending(timer)) {

		detach_timer(timer, 0);

		ret = 1;

	} else {

		if (pending_only)

			goto out_unlock;

	}



	debug_timer_activate(timer);
@@ -629,42 +635,28 @@ int __mod_timer(struct timer_list *timer, unsigned long expires) 


	timer->expires = expires;

	internal_add_timer(base, timer);



out_unlock:

	spin_unlock_irqrestore(&base->lock, flags);



	return ret;

}



EXPORT_SYMBOL(__mod_timer);



/**

 * add_timer_on - start a timer on a particular CPU

 * @timer: the timer to be added

 * @cpu: the CPU to start it on

 * mod_timer_pending - modify a pending timer's timeout

 * @timer: the pending timer to be modified

 * @expires: new timeout in jiffies

 *

 * This is not very scalable on SMP. Double adds are not possible.

 * mod_timer_pending() is the same for pending timers as mod_timer(),

 * but will not re-activate and modify already deleted timers.

 *

 * It is useful for unserialized use of timers.

 */

void add_timer_on(struct timer_list *timer, int cpu)

int mod_timer_pending(struct timer_list *timer, unsigned long expires)

{

	struct tvec_base *base = per_cpu(tvec_bases, cpu);

	unsigned long flags;



	timer_stats_timer_set_start_info(timer);

	BUG_ON(timer_pending(timer) || !timer->function);

	spin_lock_irqsave(&base->lock, flags);

	timer_set_base(timer, base);

	debug_timer_activate(timer);

	internal_add_timer(base, timer);

	/*

	 * Check whether the other CPU is idle and needs to be

	 * triggered to reevaluate the timer wheel when nohz is

	 * active. We are protected against the other CPU fiddling

	 * with the timer by holding the timer base lock. This also

	 * makes sure that a CPU on the way to idle can not evaluate

	 * the timer wheel.

	 */

	wake_up_idle_cpu(cpu);

	spin_unlock_irqrestore(&base->lock, flags);

	return __mod_timer(timer, expires, true);

}

EXPORT_SYMBOL(mod_timer_pending);



/**

 * mod_timer - modify a timer's timeout
@@ -688,9 +680,6 @@ void add_timer_on(struct timer_list *timer, int cpu) 
 */

int mod_timer(struct timer_list *timer, unsigned long expires)

{

	BUG_ON(!timer->function);



	timer_stats_timer_set_start_info(timer);

	/*

	 * This is a common optimization triggered by the

	 * networking code - if the timer is re-modified
@@ -699,11 +688,61 @@ int mod_timer(struct timer_list *timer, unsigned long expires) 
	if (timer->expires == expires && timer_pending(timer))

		return 1;



	return __mod_timer(timer, expires);

	return __mod_timer(timer, expires, false);

}



EXPORT_SYMBOL(mod_timer);



/**

 * add_timer - start a timer

 * @timer: the timer to be added

 *

 * The kernel will do a ->function(->data) callback from the

 * timer interrupt at the ->expires point in the future. The

 * current time is 'jiffies'.

 *

 * The timer's ->expires, ->function (and if the handler uses it, ->data)

 * fields must be set prior calling this function.

 *

 * Timers with an ->expires field in the past will be executed in the next

 * timer tick.

 */

void add_timer(struct timer_list *timer)

{

	BUG_ON(timer_pending(timer));

	mod_timer(timer, timer->expires);

}

EXPORT_SYMBOL(add_timer);



/**

 * add_timer_on - start a timer on a particular CPU

 * @timer: the timer to be added

 * @cpu: the CPU to start it on

 *

 * This is not very scalable on SMP. Double adds are not possible.

 */

void add_timer_on(struct timer_list *timer, int cpu)

{

	struct tvec_base *base = per_cpu(tvec_bases, cpu);

	unsigned long flags;



	timer_stats_timer_set_start_info(timer);

	BUG_ON(timer_pending(timer) || !timer->function);

	spin_lock_irqsave(&base->lock, flags);

	timer_set_base(timer, base);

	debug_timer_activate(timer);

	internal_add_timer(base, timer);

	/*

	 * Check whether the other CPU is idle and needs to be

	 * triggered to reevaluate the timer wheel when nohz is

	 * active. We are protected against the other CPU fiddling

	 * with the timer by holding the timer base lock. This also

	 * makes sure that a CPU on the way to idle can not evaluate

	 * the timer wheel.

	 */

	wake_up_idle_cpu(cpu);

	spin_unlock_irqrestore(&base->lock, flags);

}



/**

 * del_timer - deactive a timer.

 * @timer: the timer to be deactivated
@@ -733,7 +772,6 @@ int del_timer(struct timer_list *timer) 


	return ret;

}



EXPORT_SYMBOL(del_timer);



#ifdef CONFIG_SMP
@@ -767,7 +805,6 @@ out: 


	return ret;

}



EXPORT_SYMBOL(try_to_del_timer_sync);



/**
@@ -796,7 +833,6 @@ int del_timer_sync(struct timer_list *timer) 
		cpu_relax();

	}

}



EXPORT_SYMBOL(del_timer_sync);

#endif
@@ -1268,7 +1304,7 @@ signed long __sched schedule_timeout(signed long timeout) 
	expire = timeout + jiffies;



	setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);

	__mod_timer(&timer, expire);

	__mod_timer(&timer, expire, false);

	schedule();

	del_singleshot_timer_sync(&timer);