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authorIngo Molnar <mingo@elte.hu>2009-02-18 12:23:29 +0100
committerIngo Molnar <mingo@elte.hu>2009-02-18 19:26:33 +0100
commit74019224ac34b044b44a31dd89a54e3477db4896 (patch)
treebf7b04319c0c4329eb6cef0788737c14d2fa9030
parent5955c7a2cfb6a35429adea5dc480002b15ca8cfc (diff)
downloadlinaro-lsk-74019224ac34b044b44a31dd89a54e3477db4896.tar.gz
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: Stephen 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: Ingo Molnar <mingo@elte.hu>
-rw-r--r--arch/powerpc/platforms/cell/spufs/sched.c2
-rw-r--r--drivers/infiniband/hw/ipath/ipath_driver.c6
-rw-r--r--include/linux/timer.h22
-rw-r--r--kernel/relay.c2
-rw-r--r--kernel/timer.c110
5 files changed, 80 insertions, 62 deletions
diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 6a0ad196aeb..f085369301b 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -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);
}
}
diff --git a/drivers/infiniband/hw/ipath/ipath_driver.c b/drivers/infiniband/hw/ipath/ipath_driver.c
index 69c0ce321b4..cb9daa6ac02 100644
--- a/drivers/infiniband/hw/ipath/ipath_driver.c
+++ b/drivers/infiniband/hw/ipath/ipath_driver.c
@@ -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);
}
}
diff --git a/include/linux/timer.h b/include/linux/timer.h
index daf9685b861..e2d662e3416 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -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);
diff --git a/kernel/relay.c b/kernel/relay.c
index 9d79b7854fa..8f2179c8056 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -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;
diff --git a/kernel/timer.c b/kernel/timer.c
index 13dd64fe143..9b77fc9a9ac 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -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
@@ -699,12 +688,62 @@ 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);