提交 74019224 编写于 作者: I Ingo Molnar

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: NStephen 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: NIngo Molnar <mingo@elte.hu>
上级 5955c7a2
......@@ -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);
}
}
......
......@@ -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);
}
}
......
......@@ -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);
......
......@@ -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;
......
......@@ -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 @@ int try_to_del_timer_sync(struct timer_list *timer)
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);
......
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