[PATCH v2 1/3] ftrace: add tracepoint for timer

Xiao Guangrong
2009-07-06T09:39:29Z

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 9385ad5..13f943b 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -523,6 +523,30 @@ 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)
@@ -551,7 +575,7 @@ 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);
@@ -570,7 +594,7 @@ 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)
@@ -631,7 +655,7 @@ __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);

@@ -783,7 +807,7 @@ 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
@@ -954,6 +978,7 @@ 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