See upstream commit:
commit f28d3d5346e97e60c81f933ac89ccf015430e5cf
Author: Anna-Maria Gleixner <anna-ma...@linutronix.de>
Date: Thu Mar 21 13:09:21 2019 +0100
timer/trace: Improve timer tracing
Timers are added to the timer wheel off by one. This is required in
case a timer is queued directly before incrementing jiffies to prevent
early timer expiry.
When reading a timer trace and relying only on the expiry time of the timer
in the timer_start trace point and on the now in the timer_expiry_entry
trace point, it seems that the timer fires late. With the current
timer_expiry_entry trace point information only now=jiffies is printed but
not the value of base->clk. This makes it impossible to draw a conclusion
to the index of base->clk and makes it impossible to examine timer problems
without additional trace points.
Therefore add the base->clk value to the timer_expire_entry trace
point, to be able to calculate the index the timer base is located at
during collecting expired timers.
Signed-off-by: Michael Jeanson <mjean...@efficios.com>
---
instrumentation/events/lttng-module/timer.h | 22 +++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/instrumentation/events/lttng-module/timer.h
b/instrumentation/events/lttng-module/timer.h
index 8703ea0..997084f 100644
--- a/instrumentation/events/lttng-module/timer.h
+++ b/instrumentation/events/lttng-module/timer.h
@@ -89,6 +89,27 @@ LTTNG_TRACEPOINT_EVENT(timer_start,
)
#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,2,0)) */
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(5,2,0))
+/**
+ * timer_expire_entry - called immediately before the timer callback
+ * @timer: pointer to struct timer_list
+ *
+ * Allows to determine the timer latency.
+ */
+LTTNG_TRACEPOINT_EVENT(timer_expire_entry,
+
+ TP_PROTO(struct timer_list *timer, unsigned long baseclk),
+
+ TP_ARGS(timer, baseclk),
+
+ TP_FIELDS(
+ ctf_integer_hex(void *, timer, timer)
+ ctf_integer(unsigned long, now, jiffies)
+ ctf_integer_hex(void *, function, timer->function)
+ ctf_integer(unsigned long, baseclk, baseclk)
+ )
+)
+#else
/**
* timer_expire_entry - called immediately before the timer callback
* @timer: pointer to struct timer_list
@@ -107,6 +128,7 @@ LTTNG_TRACEPOINT_EVENT(timer_expire_entry,
ctf_integer_hex(void *, function, timer->function)
)
)
+#endif
/**
* timer_expire_exit - called immediately after the timer callback returns
--
2.17.1
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