[PATCH v2] softirq: Add tracepoint for tasklet_entry/exit

[PATCH v2] softirq: Add tracepoint for tasklet_entry/exit

[Junwen Wu]

Usually softirq handler is pre-defined,only tasklet can be register by
driver.We expand tracepoint for tasklet_entry/exit to trace
tasklet handler.

Signed-off-by: Junwen Wu <wudaemon@163.com>
---
Changes since v1: https://lore.kernel.org/all/20220508160624.48643-1-wudaemon@163.com/
 - Used DECLARE_EVENT_CLASS (Steven Rostedt)

 include/trace/events/irq.h | 41 ++++++++++++++++++++++++++++++++++++++
 kernel/softirq.c           |  4 ++++
 2 files changed, 45 insertions(+)

diff --git a/include/trace/events/irq.h b/include/trace/events/irq.h
index eeceafaaea4c..62b7e53121da 100644
--- a/include/trace/events/irq.h
+++ b/include/trace/events/irq.h
@@ -160,6 +160,47 @@ DEFINE_EVENT(softirq, softirq_raise,
 	TP_ARGS(vec_nr)
 );
 
+DECLARE_EVENT_CLASS(tasklet,
+
+	TP_PROTO(void *func),
+
+	TP_ARGS(func),
+
+	TP_STRUCT__entry(
+		__field(        void*,     func )
+	),
+
+	TP_fast_assign(
+		__entry->func = func;
+	),
+
+	TP_printk("function=%ps", __entry->func)
+);
+
+/**
+ * tasklet_entry - called immediately when a tasklet exec
+ * @func: the callback function when a tasklet exec
+ *
+ * When used in combination with the tasklet_entry tracepoint
+ * we can determine the callback function when a tasklet exec.
+ */
+DEFINE_EVENT(tasklet, tasklet_entry,
+
+	TP_PROTO(void *func),
+
+	TP_ARGS(func)
+);
+
+/**
+ * tasklet_exit - called immediately after the tasklet handler returns
+ * @func: the callback function when a tasklet exec
+ */
+DEFINE_EVENT(tasklet, tasklet_exit,
+
+	TP_PROTO(void *func),
+
+	TP_ARGS(func)
+);
 #endif /*  _TRACE_IRQ_H */
 
 /* This part must be outside protection */
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 41f470929e99..79b3814ad166 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -780,10 +780,14 @@ static void tasklet_action_common(struct softirq_action *a,
 		if (tasklet_trylock(t)) {
 			if (!atomic_read(&t->count)) {
 				if (tasklet_clear_sched(t)) {
+					trace_tasklet_entry(t->use_callback ? (void *)t->callback
+							: (void *)t->func);
 					if (t->use_callback)
 						t->callback(t);
 					else
 						t->func(t->data);
+					trace_tasklet_exit(t->use_callback ? (void *)t->callback
+							: (void *)t->func);
 				}
 				tasklet_unlock(t);
 				continue;
-- 
2.25.1

Re: [PATCH v2] softirq: Add tracepoint for tasklet_entry/exit

[Davidlohr Bueso]

On Sat, 28 May 2022, Junwen Wu wrote:

>Usually softirq handler is pre-defined,only tasklet can be register by
>driver.We expand tracepoint for tasklet_entry/exit to trace
>tasklet handler.

Tasklets are artifacts of the past, and deprecated years ago. Lets not
add to moot interfaces. Everything should be converted to run in task
context.

Thanks,
Davidlohr