[PATCH v2 1/2] ftrace: add tracepoint for timer

[PATCH v2 1/2] ftrace: add tracepoint for timer

[Xiao Guangrong]

This patch is modify from Mathieu's patch base on Ingo's suggestion, the
original patch can be found here:
	http://marc.info/?l=linux-kernel&m=123791201816247&w=2

Great thanks to Thomas for giving me so many valuable advices.

Those tracepoints are wanted and useful:
1: We can detect a timer's delay
2: We can monitor the lifecycle and behaviors of a timer

Thus they help in analysing and debuging.

Example ftrace output:
   insmod-3743  [001] 217105.738770: timer_init: timer=e0b3e4c8
   insmod-3743  [001] 217105.738868: timer_start: timer=e0b3e4c8 func=timer_fun expires=442863 timeout=50
   <idle>-0     [001] 217105.935436: timer_expire: timer=e0b3e4c8 func=timer_fun jiffies=442863
   <idle>-0     [001] 217105.935440: timer_cancel: timer=e0b3e4c8 func=timer_fun

We expect the timer expires at 442863, after 50 jiffies, actually the timer
expires at 442863, so it is delayed by 0 jiffies.

Changelog v1->v2:
1: Add jiffies info into timer
2: Combine debugobjects and trace as Thomas's suggestion
 
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 include/trace/events/timer.h |   82 ++++++++++++++++++++++++++++++++++++++++++
 kernel/timer.c               |   33 +++++++++++++++--
 2 files changed, 111 insertions(+), 4 deletions(-)

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index 6e7beb5..e9c51ee 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -110,6 +110,88 @@ TRACE_EVENT(hrtimer_exit,
 			"HRTIMER_RESTART" : "HRTIMER_NORESTART")
 );
 
+TRACE_EVENT(timer_init,
+
+	TP_PROTO(struct timer_list *timer),
+
+	TP_ARGS(timer),
+
+	TP_STRUCT__entry(
+		__field( void *,	timer	)
+	),
+
+	TP_fast_assign(
+		__entry->timer	= timer;
+	),
+
+	TP_printk("timer=%p", __entry->timer)
+);
+
+TRACE_EVENT(timer_start,
+
+	TP_PROTO(struct timer_list *timer, unsigned long expires),
+
+	TP_ARGS(timer, expires),
+
+	TP_STRUCT__entry(
+		__field( void *,	timer		)
+		__field( void *,	function	)
+		__field( unsigned long,	expires		)
+		__field( int,		timeout		)
+	),
+
+	TP_fast_assign(
+		__entry->timer		= timer;
+		__entry->function	= timer->function;
+		__entry->expires	= expires;
+		__entry->timeout	= timer->expires - jiffies;
+	),
+
+	TP_printk("timer=%p func=%pf expires=%lu timeout=%d", __entry->timer,
+		  __entry->function, __entry->expires, __entry->timeout)
+);
+
+TRACE_EVENT(timer_expire,
+
+	TP_PROTO(struct timer_list *timer),
+
+	TP_ARGS(timer),
+
+	TP_STRUCT__entry(
+		__field( void *,	timer		)
+		__field( void *,	function	)
+		__field( unsigned long,	jiffies		)
+	),
+
+	TP_fast_assign(
+		__entry->timer		= timer;
+		__entry->function	= timer->function;
+		__entry->jiffies	= jiffies;
+	),
+
+	TP_printk("timer=%p func=%pf jiffies=%lu", __entry->timer,
+		  __entry->function, __entry->jiffies)
+);
+
+TRACE_EVENT(timer_cancel,
+
+	TP_PROTO(struct timer_list *timer),
+
+	TP_ARGS(timer),
+
+	TP_STRUCT__entry(
+		__field( void *,	timer		)
+		__field( void *,	function	)
+	),
+
+	TP_fast_assign(
+		__entry->timer		= timer;
+		__entry->function	= timer->function;
+	),
+
+	TP_printk("timer=%p func=%pf", __entry->timer, __entry->function)
+);
+
 #endif /*  _TRACE_TIMER_H */
 
 /* This part must be outside protection */
diff --git a/kernel/timer.c b/kernel/timer.c
index d07c900..11660c7 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -521,6 +521,30 @@ static inline void debug_timer_activate(struct timer_list *timer) { }
 static inline void debug_timer_deactivate(struct timer_list *timer) { }
 #endif
 
+static inline void debug_and_trace_timer_init(struct timer_list *timer)
+{
+	debug_timer_init(timer);
+	trace_timer_init(timer);
+}
+
+static inline void
+debug_and_trace_timer_activate(struct timer_list *timer, unsigned long expires)
+{
+	debug_timer_activate(timer);
+	trace_timer_start(timer, expires);
+}
+
+static inline void debug_and_trace_timer_expire(struct timer_list *timer)
+{
+	trace_timer_expire(timer);
+}
+
+static inline void debug_and_trace_timer_deactivate(struct timer_list *timer)
+{
+	debug_timer_deactivate(timer);
+	trace_timer_cancel(timer);
+}
+
 static void __init_timer(struct timer_list *timer,
 			 const char *name,
 			 struct lock_class_key *key)
@@ -549,7 +573,7 @@ void init_timer_key(struct timer_list *timer,
 		    const char *name,
 		    struct lock_class_key *key)
 {
-	debug_timer_init(timer);
+	debug_and_trace_timer_init(timer);
 	__init_timer(timer, name, key);
 }
 EXPORT_SYMBOL(init_timer_key);
@@ -568,7 +592,7 @@ static inline void detach_timer(struct timer_list *timer,
 {
 	struct list_head *entry = &timer->entry;
 
-	debug_timer_deactivate(timer);
+	debug_and_trace_timer_deactivate(timer);
 
 	__list_del(entry->prev, entry->next);
 	if (clear_pending)
@@ -629,7 +653,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
 			goto out_unlock;
 	}
 
-	debug_timer_activate(timer);
+	debug_and_trace_timer_activate(timer, expires);
 
 	new_base = __get_cpu_var(tvec_bases);
 
@@ -781,7 +805,7 @@ void add_timer_on(struct timer_list *timer, int cpu)
 	BUG_ON(timer_pending(timer) || !timer->function);
 	spin_lock_irqsave(&base->lock, flags);
 	timer_set_base(timer, base);
-	debug_timer_activate(timer);
+	debug_and_trace_timer_activate(timer, timer->expires);
 	internal_add_timer(base, timer);
 	/*
 	 * Check whether the other CPU is idle and needs to be
@@ -952,6 +976,7 @@ static inline void __run_timers(struct tvec_base *base)
 			unsigned long data;
 
 			timer = list_first_entry(head, struct timer_list,entry);
+			debug_and_trace_timer_expire(timer);
 			fn = timer->function;
 			data = timer->data;
 
-- 
1.6.1.2

[PATCH 2/2 v2] ftrace: add tracepoint for hrtimer

[Xiao Guangrong]

Those tracepoints are wanted and useful:
1: We can detect a hrtimer's delay
2: We can monitor the lifecycle and behaviors of a hrtimer

Thus they help in analysing and debuging.

Great thanks to Thomas for giving me so many valuable advices.

Example ftrace output:
insmod-3821  [001]  3192.239314: hrtimer_init: timer=d08a1480 clockid=CLOCK_REALTIME mode=HRTIMER_MODE_ABS
insmod-3821  [001]  3192.239335: hrtimer_start: timer=d08a1480 func=hrtimer_fun expires=1245162841000000000 ns softexpires=1245162841000000000 ns
<idle>-0     [001]  3201.506127: hrtimer_expire: timer=d08a1480 func=hrtimer_fun now=1245162841010241858
<idle>-0     [001]  3201.506129: hrtimer_cancel: timer=d08a1480 func=hrtimer_fun
 
We expect the hrtimer expires at 1245162841000000000 ns, actually the
hrtimer expires at 1245162841010241858 ns, so it is delayed by
1245162841010241858- 1245162841000000000 = 10241858 ns.

Changelog v1->v2:
1: Remove ktime_to_ns() in TP_fast_assign()
2: Combine debugobjects and trace as Thomas's suggestion

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 include/trace/events/timer.h |   90 ++++++++++++++++++++++++++++++++++++++++++
 kernel/hrtimer.c             |   38 +++++++++++++++--
 2 files changed, 123 insertions(+), 5 deletions(-)

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index e9c51ee..8ffb2e2 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -192,6 +192,96 @@ TRACE_EVENT(timer_cancel,
 	TP_printk("timer=%p func=%pf", __entry->timer, __entry->function)
 );
 
+TRACE_EVENT(hrtimer_init,
+
+	TP_PROTO(struct hrtimer *timer, clockid_t clockid, enum hrtimer_mode mode),
+
+	TP_ARGS(timer, clockid, mode),
+
+	TP_STRUCT__entry(
+		__field( void *,		timer		)
+		__field( clockid_t,		clockid		)
+		__field( enum hrtimer_mode,	mode		)
+	),
+
+	TP_fast_assign(
+		__entry->timer		= timer;
+		__entry->clockid	= clockid;
+		__entry->mode		= mode;
+	),
+
+	TP_printk("timer=%p clockid=%s mode=%s", __entry->timer,
+		  __entry->clockid == CLOCK_REALTIME ?
+			"CLOCK_REALTIME" : "CLOCK_MONOTONIC",
+		  __entry->mode == HRTIMER_MODE_ABS ?
+			"HRTIMER_MODE_ABS" : "HRTIMER_MODE_REL")
+);
+
+TRACE_EVENT(hrtimer_start,
+
+	TP_PROTO(struct hrtimer *timer),
+
+	TP_ARGS(timer),
+
+	TP_STRUCT__entry(
+		__field( void *,	timer		)
+		__field( void *,	function	)
+		__field( s64,		expires		)
+		__field( s64,		softexpires	)
+	),
+
+	TP_fast_assign(
+		__entry->timer		= timer;
+		__entry->function	= timer->function;
+		__entry->expires	= hrtimer_get_expires(timer).tv64;
+		__entry->softexpires	= hrtimer_get_softexpires(timer).tv64;
+	),
+
+	TP_printk("timer=%p func=%pf expires=%llu ns softexpires=%llu ns",
+		  __entry->timer, __entry->function,
+		 (unsigned long long)__entry->expires,
+		 (unsigned long long)__entry->softexpires)
+);
+
+TRACE_EVENT(hrtimer_expire,
+
+	TP_PROTO(struct hrtimer *timer, s64 now),
+
+	TP_ARGS(timer, now),
+
+	TP_STRUCT__entry(
+		__field( void *,	timer		)
+		__field( void *,	function	)
+		__field( s64,		now		)
+	),
+
+	TP_fast_assign(
+		__entry->timer		= timer;
+		__entry->function	= timer->function;
+		__entry->now		= now;
+	),
+
+	TP_printk("timer=%p func=%pf now=%llu", __entry->timer, __entry->function,
+		 (unsigned long long)__entry->now)
+);
+
+TRACE_EVENT(hrtimer_cancel,
+
+	TP_PROTO(struct hrtimer *timer),
+	TP_ARGS(timer),
+	TP_STRUCT__entry(
+		__field( void *,	timer		)
+		__field( void *,	function	)
+	),
+
+	TP_fast_assign(
+		__entry->timer		= timer;
+		__entry->function	= timer->function;
+	),
+
+	TP_printk("timer=%p func=%pf", __entry->timer, __entry->function)
+);
+
 #endif /*  _TRACE_TIMER_H */
 
 /* This part must be outside protection */
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index b42429f..f75ba95 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -491,6 +491,32 @@ static inline void debug_hrtimer_activate(struct hrtimer *timer) { }
 static inline void debug_hrtimer_deactivate(struct hrtimer *timer) { }
 #endif
 
+static inline void
+debug_and_trace_hrtimer_init(struct hrtimer *timer, clockid_t clockid,
+                             enum hrtimer_mode mode)
+{
+	debug_hrtimer_init(timer);
+	trace_hrtimer_init(timer, clockid, mode);
+}
+
+static inline void debug_and_trace_hrtimer_activate(struct hrtimer *timer)
+{
+	debug_hrtimer_activate(timer);
+	trace_hrtimer_start(timer);
+}
+
+static inline void debug_and_trace_hrtimer_expire(struct hrtimer *timer,
+                                                  s64 now)
+{
+	trace_hrtimer_expire(timer, now);
+}
+
+static inline void debug_and_trace_hrtimer_deactivate(struct hrtimer *timer)
+{
+	debug_hrtimer_deactivate(timer);
+	trace_hrtimer_cancel(timer);
+}
+
 /* High resolution timer related functions */
 #ifdef CONFIG_HIGH_RES_TIMERS
 
@@ -847,7 +873,7 @@ static int enqueue_hrtimer(struct hrtimer *timer,
 	struct hrtimer *entry;
 	int leftmost = 1;
 
-	debug_hrtimer_activate(timer);
+	debug_and_trace_hrtimer_activate(timer);
 
 	/*
 	 * Find the right place in the rbtree:
@@ -933,7 +959,7 @@ remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
 		 * reprogramming happens in the interrupt handler. This is a
 		 * rare case and less expensive than a smp call.
 		 */
-		debug_hrtimer_deactivate(timer);
+		debug_and_trace_hrtimer_deactivate(timer);
 		timer_stats_hrtimer_clear_start_info(timer);
 		reprogram = base->cpu_base == &__get_cpu_var(hrtimer_bases);
 		__remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE,
@@ -1167,7 +1193,7 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 		  enum hrtimer_mode mode)
 {
-	debug_hrtimer_init(timer);
+	debug_and_trace_hrtimer_init(timer, clock_id, mode);
 	__hrtimer_init(timer, clock_id, mode);
 }
 EXPORT_SYMBOL_GPL(hrtimer_init);
@@ -1200,7 +1226,7 @@ static void __run_hrtimer(struct hrtimer *timer)
 
 	WARN_ON(!irqs_disabled());
 
-	debug_hrtimer_deactivate(timer);
+	debug_and_trace_hrtimer_deactivate(timer);
 	__remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
 	timer_stats_account_hrtimer(timer);
 	fn = timer->function;
@@ -1316,6 +1342,7 @@ void hrtimer_interrupt(struct clock_event_device *dev)
 				break;
 			}
 
+			debug_and_trace_hrtimer_expire(timer, basenow.tv64);
 			__run_hrtimer(timer);
 		}
 		spin_unlock(&cpu_base->lock);
@@ -1434,6 +1461,7 @@ void hrtimer_run_queues(void)
 					hrtimer_get_expires_tv64(timer))
 				break;
 
+			debug_and_trace_hrtimer_expire(timer, base->softirq_time.tv64);
 			__run_hrtimer(timer);
 		}
 		spin_unlock(&cpu_base->lock);
@@ -1610,7 +1638,7 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
 	while ((node = rb_first(&old_base->active))) {
 		timer = rb_entry(node, struct hrtimer, node);
 		BUG_ON(hrtimer_callback_running(timer));
-		debug_hrtimer_deactivate(timer);
+		debug_and_trace_hrtimer_deactivate(timer);
 
 		/*
 		 * Mark it as STATE_MIGRATE not INACTIVE otherwise the
-- 
1.6.1.2

Re: [PATCH v2 1/2] ftrace: add tracepoint for timer

[Frederic Weisbecker]

On Wed, Jun 17, 2009 at 05:39:19PM +0800, Xiao Guangrong wrote:
> This patch is modify from Mathieu's patch base on Ingo's suggestion, the
> original patch can be found here:
> 	http://marc.info/?l=linux-kernel&m=123791201816247&w=2
> 
> Great thanks to Thomas for giving me so many valuable advices.
> 
> Those tracepoints are wanted and useful:
> 1: We can detect a timer's delay
> 2: We can monitor the lifecycle and behaviors of a timer
> 
> Thus they help in analysing and debuging.
> 
> Example ftrace output:
>    insmod-3743  [001] 217105.738770: timer_init: timer=e0b3e4c8
>    insmod-3743  [001] 217105.738868: timer_start: timer=e0b3e4c8 func=timer_fun expires=442863 timeout=50
>    <idle>-0     [001] 217105.935436: timer_expire: timer=e0b3e4c8 func=timer_fun jiffies=442863
>    <idle>-0     [001] 217105.935440: timer_cancel: timer=e0b3e4c8 func=timer_fun
> 
> We expect the timer expires at 442863, after 50 jiffies, actually the timer
> expires at 442863, so it is delayed by 0 jiffies.
> 
> Changelog v1->v2:
> 1: Add jiffies info into timer
> 2: Combine debugobjects and trace as Thomas's suggestion
>  
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>


Thomas, are you fine with these patches?
If so, I can prepare a pull request to Ingo, unless he prefers to
apply them himself.

Thanks,
Frederic.



> ---
>  include/trace/events/timer.h |   82 ++++++++++++++++++++++++++++++++++++++++++
>  kernel/timer.c               |   33 +++++++++++++++--
>  2 files changed, 111 insertions(+), 4 deletions(-)
> 
> diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
> index 6e7beb5..e9c51ee 100644
> --- a/include/trace/events/timer.h
> +++ b/include/trace/events/timer.h
> @@ -110,6 +110,88 @@ TRACE_EVENT(hrtimer_exit,
>  			"HRTIMER_RESTART" : "HRTIMER_NORESTART")
>  );
>  
> +TRACE_EVENT(timer_init,
> +
> +	TP_PROTO(struct timer_list *timer),
> +
> +	TP_ARGS(timer),
> +
> +	TP_STRUCT__entry(
> +		__field( void *,	timer	)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->timer	= timer;
> +	),
> +
> +	TP_printk("timer=%p", __entry->timer)
> +);
> +
> +TRACE_EVENT(timer_start,
> +
> +	TP_PROTO(struct timer_list *timer, unsigned long expires),
> +
> +	TP_ARGS(timer, expires),
> +
> +	TP_STRUCT__entry(
> +		__field( void *,	timer		)
> +		__field( void *,	function	)
> +		__field( unsigned long,	expires		)
> +		__field( int,		timeout		)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->timer		= timer;
> +		__entry->function	= timer->function;
> +		__entry->expires	= expires;
> +		__entry->timeout	= timer->expires - jiffies;
> +	),
> +
> +	TP_printk("timer=%p func=%pf expires=%lu timeout=%d", __entry->timer,
> +		  __entry->function, __entry->expires, __entry->timeout)
> +);
> +
> +TRACE_EVENT(timer_expire,
> +
> +	TP_PROTO(struct timer_list *timer),
> +
> +	TP_ARGS(timer),
> +
> +	TP_STRUCT__entry(
> +		__field( void *,	timer		)
> +		__field( void *,	function	)
> +		__field( unsigned long,	jiffies		)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->timer		= timer;
> +		__entry->function	= timer->function;
> +		__entry->jiffies	= jiffies;
> +	),
> +
> +	TP_printk("timer=%p func=%pf jiffies=%lu", __entry->timer,
> +		  __entry->function, __entry->jiffies)
> +);
> +
> +TRACE_EVENT(timer_cancel,
> +
> +	TP_PROTO(struct timer_list *timer),
> +
> +	TP_ARGS(timer),
> +
> +	TP_STRUCT__entry(
> +		__field( void *,	timer		)
> +		__field( void *,	function	)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->timer		= timer;
> +		__entry->function	= timer->function;
> +	),
> +
> +	TP_printk("timer=%p func=%pf", __entry->timer, __entry->function)
> +);
> +
>  #endif /*  _TRACE_TIMER_H */
>  
>  /* This part must be outside protection */
> diff --git a/kernel/timer.c b/kernel/timer.c
> index d07c900..11660c7 100644
> --- a/kernel/timer.c
> +++ b/kernel/timer.c
> @@ -521,6 +521,30 @@ static inline void debug_timer_activate(struct timer_list *timer) { }
>  static inline void debug_timer_deactivate(struct timer_list *timer) { }
>  #endif
>  
> +static inline void debug_and_trace_timer_init(struct timer_list *timer)
> +{
> +	debug_timer_init(timer);
> +	trace_timer_init(timer);
> +}
> +
> +static inline void
> +debug_and_trace_timer_activate(struct timer_list *timer, unsigned long expires)
> +{
> +	debug_timer_activate(timer);
> +	trace_timer_start(timer, expires);
> +}
> +
> +static inline void debug_and_trace_timer_expire(struct timer_list *timer)
> +{
> +	trace_timer_expire(timer);
> +}
> +
> +static inline void debug_and_trace_timer_deactivate(struct timer_list *timer)
> +{
> +	debug_timer_deactivate(timer);
> +	trace_timer_cancel(timer);
> +}
> +
>  static void __init_timer(struct timer_list *timer,
>  			 const char *name,
>  			 struct lock_class_key *key)
> @@ -549,7 +573,7 @@ void init_timer_key(struct timer_list *timer,
>  		    const char *name,
>  		    struct lock_class_key *key)
>  {
> -	debug_timer_init(timer);
> +	debug_and_trace_timer_init(timer);
>  	__init_timer(timer, name, key);
>  }
>  EXPORT_SYMBOL(init_timer_key);
> @@ -568,7 +592,7 @@ static inline void detach_timer(struct timer_list *timer,
>  {
>  	struct list_head *entry = &timer->entry;
>  
> -	debug_timer_deactivate(timer);
> +	debug_and_trace_timer_deactivate(timer);
>  
>  	__list_del(entry->prev, entry->next);
>  	if (clear_pending)
> @@ -629,7 +653,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
>  			goto out_unlock;
>  	}
>  
> -	debug_timer_activate(timer);
> +	debug_and_trace_timer_activate(timer, expires);
>  
>  	new_base = __get_cpu_var(tvec_bases);
>  
> @@ -781,7 +805,7 @@ void add_timer_on(struct timer_list *timer, int cpu)
>  	BUG_ON(timer_pending(timer) || !timer->function);
>  	spin_lock_irqsave(&base->lock, flags);
>  	timer_set_base(timer, base);
> -	debug_timer_activate(timer);
> +	debug_and_trace_timer_activate(timer, timer->expires);
>  	internal_add_timer(base, timer);
>  	/*
>  	 * Check whether the other CPU is idle and needs to be
> @@ -952,6 +976,7 @@ static inline void __run_timers(struct tvec_base *base)
>  			unsigned long data;
>  
>  			timer = list_first_entry(head, struct timer_list,entry);
> +			debug_and_trace_timer_expire(timer);
>  			fn = timer->function;
>  			data = timer->data;
>  
> -- 
> 1.6.1.2
> 
> 

Re: [PATCH v2 1/2] ftrace: add tracepoint for timer

[Xiao Guangrong]

Frederic Weisbecker wrote:
> On Wed, Jun 17, 2009 at 05:39:19PM +0800, Xiao Guangrong wrote:
>> This patch is modify from Mathieu's patch base on Ingo's suggestion, the
>> original patch can be found here:
>> 	http://marc.info/?l=linux-kernel&m=123791201816247&w=2
>>
>> Great thanks to Thomas for giving me so many valuable advices.
>>
>> Those tracepoints are wanted and useful:
>> 1: We can detect a timer's delay
>> 2: We can monitor the lifecycle and behaviors of a timer
>>
>> Thus they help in analysing and debuging.
>>
>> Example ftrace output:
>>    insmod-3743  [001] 217105.738770: timer_init: timer=e0b3e4c8
>>    insmod-3743  [001] 217105.738868: timer_start: timer=e0b3e4c8 func=timer_fun expires=442863 timeout=50
>>    <idle>-0     [001] 217105.935436: timer_expire: timer=e0b3e4c8 func=timer_fun jiffies=442863
>>    <idle>-0     [001] 217105.935440: timer_cancel: timer=e0b3e4c8 func=timer_fun
>>
>> We expect the timer expires at 442863, after 50 jiffies, actually the timer
>> expires at 442863, so it is delayed by 0 jiffies.
>>
>> Changelog v1->v2:
>> 1: Add jiffies info into timer
>> 2: Combine debugobjects and trace as Thomas's suggestion
>>  
>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
>> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> 
> 
> Thomas, are you fine with these patches?
> If so, I can prepare a pull request to Ingo, unless he prefers to
> apply them himself.
> 

Hi Thomas,

What is your opinion on this patch?
Can I get your acked-by if you think this patch is useful for us?

Thanks,
Xiao

> Thanks,
> Frederic.
> 
>