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

On Wed, 27 May 2009, Xiao Guangrong wrote:
+ TP_printk("timer=%p func=%pf expires=%lu cpu=%d", __entry->timer,
+ __entry->function, __entry->expires, __entry->cpu)
+);

How do we connect the trace to the jiffies value when the timer
was started ?


ftrace already have time information in trace event's output, we can use it instead

Hmm, I'm not sure whether we can see the jiffies value there, but ok.

@@ -547,6 +550,7 @@ void init_timer_key(struct timer_list *timer,
{
debug_timer_init(timer);
__init_timer(timer, name, key);
+ trace_timer_init(timer);

Can we please avoid to have two debug calls in one 2 line function ?


debug_timer_init() must call before object's init, but tracepoint have to call
after object's init beacuse if we move the tracepoint to before object init, the
object has no data yet.

Err.

+ 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)
+);

Is timer different before and after the __init_timer call ?

}
EXPORT_SYMBOL(init_timer_key);

@@ -565,6 +569,7 @@ static inline void detach_timer(struct timer_list *timer,
struct list_head *entry = &timer->entry;

debug_timer_deactivate(timer);
+ trace_timer_cancel(timer);

Ditto. Please create one debug entity which covers both.


IMHO, we can't create one entity for init event, so we do better detach other event.

See above.

Thanks,

tglx
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