tracing/timers: Enhance timer_start tracepoint

For starting a timer, the timer is enqueued into a bucket of the timer
wheel. The bucket expiry is the defacto expiry of the timer but it is not
equal the timer expiry because of increasing granularity when bucket is in
a higher level of the wheel. To be able to figure out in a trace whether a
timer expired in time or not, the bucket expiry time is required as well.

Add bucket expiry time to the timer_start tracepoint and thereby simplify
the arguments.

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20231201092654.34614-5-anna-maria@linutronix.de

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index b4bc2828fa09f05b0f36a7ccbbaf82fc44351307..99ada928d44500cde1d33852dcdb8083d0569f9e 100644 (file)
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -46,22 +46,21 @@ DEFINE_EVENT(timer_class, timer_init,
 
 /**
  * timer_start - called when the timer is started
- * @timer:     pointer to struct timer_list
- * @expires:   the timers expiry time
- * @flags:     the timers flags
+ * @timer:             pointer to struct timer_list
+ * @bucket_expiry:     the bucket expiry time
  */
 TRACE_EVENT(timer_start,
 
        TP_PROTO(struct timer_list *timer,
-               unsigned long expires,
-               unsigned int flags),
+               unsigned long bucket_expiry),
 
-       TP_ARGS(timer, expires, flags),
+       TP_ARGS(timer, bucket_expiry),
 
        TP_STRUCT__entry(
                __field( void *,        timer           )
                __field( void *,        function        )
                __field( unsigned long, expires         )
+               __field( unsigned long, bucket_expiry   )
                __field( unsigned long, now             )
                __field( unsigned int,  flags           )
        ),
@@ -69,15 +68,16 @@ TRACE_EVENT(timer_start,
        TP_fast_assign(
                __entry->timer          = timer;
                __entry->function       = timer->function;
-               __entry->expires        = expires;
+               __entry->expires        = timer->expires;
+               __entry->bucket_expiry  = bucket_expiry;
                __entry->now            = jiffies;
-               __entry->flags          = flags;
+               __entry->flags          = timer->flags;
        ),
 
-       TP_printk("timer=%p function=%ps expires=%lu [timeout=%ld] cpu=%u idx=%u flags=%s",
+       TP_printk("timer=%p function=%ps expires=%lu [timeout=%ld] bucket_expiry=%lu cpu=%u idx=%u flags=%s",
                  __entry->timer, __entry->function, __entry->expires,
                  (long)__entry->expires - __entry->now,
-                 __entry->flags & TIMER_CPUMASK,
+                 __entry->bucket_expiry, __entry->flags & TIMER_CPUMASK,
                  __entry->flags >> TIMER_ARRAYSHIFT,
                  decode_timer_flags(__entry->flags & TIMER_TRACE_FLAGMASK))
 );

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 63a8ce7177dd49b76c7e0b82400d91bebe08f126..a81d793a43d0cd9728fdfcc9cb16e697646d0857 100644 (file)
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -606,7 +606,7 @@ static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
        __set_bit(idx, base->pending_map);
        timer_set_idx(timer, idx);
 
-       trace_timer_start(timer, timer->expires, timer->flags);
+       trace_timer_start(timer, bucket_expiry);
 
        /*
         * Check whether this is the new first expiring timer. The