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tracing: timer: Add deferrable flag to timer_start

PATCH Superseded Badhri Jagan Sridharan 2 participants 2 messages May 6, 2015

Subsystems (3)
Tracing High-resolution timers, timer wheel, clockevents Posix clocks and timers
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Badhri Jagan Sridharan

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#0 lore raw

PATCH v3 1/1 tracing: timer: Add deferrable flag to timer_start

The timer_start event now shows whether the timer is deferrable in case of a low-res timer. The debug_activate function now includes deferrable flag while calling trace_timer_start event.

Signed-off-by Badhri Jagan Sridharan <[email protected]>

---
Changelog since v2:
- fixed indentation

Changelog since v1:
- fixed indentation
- moved deferrable flag checking to tracing code

 include/trace/events/timer.h | 12 ++++++++----
 kernel/time/timer.c          |  3 ++-
 2 files changed, 10 insertions(+), 5 deletions(-)
include/trace/events/timer.h +8 -4
index 68c2c20..342d741 100644
@@ -43,15 +43,17 @@ DEFINE_EVENT(timer_class, timer_init,
  */
 TRACE_EVENT(timer_start,
 
-	TP_PROTO(struct timer_list *timer, unsigned long expires),
+	TP_PROTO(struct timer_list *timer,
+		unsigned long expires, char deferrable),
 
-	TP_ARGS(timer, expires),
+	TP_ARGS(timer, expires, deferrable),
 
 	TP_STRUCT__entry(
 		__field( void *,	timer		)
 		__field( void *,	function	)
 		__field( unsigned long,	expires		)
 		__field( unsigned long,	now		)
+		__field( char,		deferrable	)
 	),
 
 	TP_fast_assign(

@@ -59,11 +61,13 @@ TRACE_EVENT(timer_start,
 		__entry->function	= timer->function;
 		__entry->expires	= expires;
 		__entry->now		= jiffies;
+		__entry->deferrable     = deferrable;
 	),
 
-	TP_printk("timer=%p function=%pf expires=%lu [timeout=%ld]",
+	TP_printk("timer=%p function=%pf expires=%lu [timeout=%ld] defer=%c",
 		  __entry->timer, __entry->function, __entry->expires,
-		  (long)__entry->expires - __entry->now)
+		  (long)__entry->expires - __entry->now,
+		  __entry->deferrable > 0 ? 'y':'n')
 );
 
 /**
kernel/time/timer.c +2 -1
index 2ece3aa..e5588da 100644
@@ -648,7 +648,8 @@ static inline void
 debug_activate(struct timer_list *timer, unsigned long expires)
 {
 	debug_timer_activate(timer);
-	trace_timer_start(timer, expires);
+	trace_timer_start(timer, expires,
+		tbase_get_deferrable(timer->base));
 }
 
 static inline void debug_deactivate(struct timer_list *timer)
Signature · 1 line
2.2.0.rc0.207.ga3a616c
maintainer
#1 lore raw
Quoted 11 lines · On Tue, 5 May 2015 19:44:10 -0700 Badhri Jagan Sridharan <[email protected]>…
include/trace/events/timer.h +2 -1
index 68c2c20..342d741 100644
@@ -43,15 +43,17 @@ DEFINE_EVENT(timer_class, timer_init,
  */
 TRACE_EVENT(timer_start,
 
-	TP_PROTO(struct timer_list *timer, unsigned long expires),
+	TP_PROTO(struct timer_list *timer,
+		unsigned long expires, char deferrable),

include/trace/events/timer.h DEFINE_EVENT(timer_class, timer_init, · line 56

Quoted 10 lines
include/trace/events/timer.h +2 -1
 
-	TP_ARGS(timer, expires),
+	TP_ARGS(timer, expires, deferrable),
 
 	TP_STRUCT__entry(
 		__field( void *,	timer		)
 		__field( void *,	function	)
 		__field( unsigned long,	expires		)
 		__field( unsigned long,	now		)
+		__field( char,		deferrable	)

I wonder if we should use int instead of char. Although TIMER_DEFERRED is defined as 0x1LU, and that tbase_get_deferrable() returns:

((unsigned int)(unsigned long)base & TIMER_DEFERRABLE);

It is still an int that is returned. If TIMER_DEFERRABLE becomes something greater than 255, then that char wont be enough to hold it.

I'm being paranoid here, but you never know what changes may happen in the future, and I rather be robust and safe. And trace events save in 4byte chunks anyway, so you wont be saving anything in the buffer by making it a char.

-- Steve

Quoted 33 lines
include/trace/events/timer.h +4 -2
 	),
 
 	TP_fast_assign(

@@ -59,11 +61,13 @@ TRACE_EVENT(timer_start,
 		__entry->function	= timer->function;
 		__entry->expires	= expires;
 		__entry->now		= jiffies;
+		__entry->deferrable     = deferrable;
 	),
 
-	TP_printk("timer=%p function=%pf expires=%lu [timeout=%ld]",
+	TP_printk("timer=%p function=%pf expires=%lu [timeout=%ld] defer=%c",
 		  __entry->timer, __entry->function, __entry->expires,
-		  (long)__entry->expires - __entry->now)
+		  (long)__entry->expires - __entry->now,
+		  __entry->deferrable > 0 ? 'y':'n')
 );
 
 /**
kernel/time/timer.c +2 -1
index 2ece3aa..e5588da 100644
@@ -648,7 +648,8 @@ static inline void
 debug_activate(struct timer_list *timer, unsigned long expires)
 {
 	debug_timer_activate(timer);
-	trace_timer_start(timer, expires);
+	trace_timer_start(timer, expires,
+		tbase_get_deferrable(timer->base));
 }
 
 static inline void debug_deactivate(struct timer_list *timer)