linux-kernel - [PATCH] tasklet: Introduce tasklet tracepoints

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Message-Id: <20200905060412.88560-1-songmuchun@bytedance.com>
Date:   Sat,  5 Sep 2020 14:04:12 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     rostedt@...dmis.org, mingo@...nel.org, tglx@...utronix.de,
        peterz@...radead.org, will@...nel.org, romain.perier@...il.com
Cc:     linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH] tasklet: Introduce tasklet tracepoints

Introduce tracepoints for tasklets just like softirq does. In this case,
we can calculate tasklet latency and know what tasklet run.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 include/trace/events/irq.h | 44 ++++++++++++++++++++++++++++++++++++++
 kernel/softirq.c           |  2 ++
 2 files changed, 46 insertions(+)

diff --git a/include/trace/events/irq.h b/include/trace/events/irq.h
index eeceafaaea4c..69a16f3a21c2 100644
--- a/include/trace/events/irq.h
+++ b/include/trace/events/irq.h
@@ -160,6 +160,50 @@ DEFINE_EVENT(softirq, softirq_raise,
 	TP_ARGS(vec_nr)
 );
 
+DECLARE_EVENT_CLASS(tasklet,
+
+	TP_PROTO(struct tasklet_struct *t),
+
+	TP_ARGS(t),
+
+	TP_STRUCT__entry(
+		__field(	void *,	callback	)
+	),
+
+	TP_fast_assign(
+		__entry->callback = t->callback;
+	),
+
+	TP_printk("callback=%ps", __entry->callback)
+);
+
+/**
+ * tasklet_entry - called immediately before the tasklet handler
+ * @t: pointer to struct tasklet_struct
+ *
+ * When used in combination with the tasklet_exit tracepoint
+ * we can determine the tasklet handler routine.
+ */
+DEFINE_EVENT(tasklet, tasklet_entry,
+
+	TP_PROTO(struct tasklet_struct *t),
+
+	TP_ARGS(t)
+);
+
+/**
+ * tasklet_exit - called immediately after the tasklet handler returns
+ * @t: pointer to struct tasklet_struct
+ *
+ * When used in combination with the tasklet_entry tracepoint
+ * we can determine the tasklet handler routine.
+ */
+DEFINE_EVENT(tasklet, tasklet_exit,
+
+	TP_PROTO(struct tasklet_struct *t),
+
+	TP_ARGS(t)
+);
 #endif /*  _TRACE_IRQ_H */
 
 /* This part must be outside protection */
diff --git a/kernel/softirq.c b/kernel/softirq.c
index bf88d7f62433..0f9f5b2cc3d3 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -553,10 +553,12 @@ static void tasklet_action_common(struct softirq_action *a,
 				if (!test_and_clear_bit(TASKLET_STATE_SCHED,
 							&t->state))
 					BUG();
+				trace_tasklet_entry(t);
 				if (t->use_callback)
 					t->callback(t);
 				else
 					t->func(t->data);
+				trace_tasklet_exit(t);
 				tasklet_unlock(t);
 				continue;
 			}
-- 
2.20.1