[PATCH v1] softirq: Add tracepoint for tasklet_entry/exit

[PATCH v1] 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>
---
 include/trace/events/irq.h | 32 ++++++++++++++++++++++++++++++++
 kernel/softirq.c           |  4 ++++
 2 files changed, 36 insertions(+)

diff --git a/include/trace/events/irq.h b/include/trace/events/irq.h
index eeceafaaea4c..d3e922dcd475 100644
--- a/include/trace/events/irq.h
+++ b/include/trace/events/irq.h
@@ -160,6 +160,38 @@ DEFINE_EVENT(softirq, softirq_raise,
 	TP_ARGS(vec_nr)
 );
 
+TRACE_EVENT(tasklet_entry,
+
+	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)
+);
+TRACE_EVENT(tasklet_exit,
+
+	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)
+);
 #endif /*  _TRACE_IRQ_H */
 
 /* This part must be outside protection */
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 41f470929e99..b3bce2b3b655 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 v1] softirq: Add tracepoint for tasklet_entry/exit

[Steven Rostedt]

On Sun,  8 May 2022 16:06:24 +0000
Junwen Wu <wudaemon@163.com> wrote:

> --- a/include/trace/events/irq.h
> +++ b/include/trace/events/irq.h
> @@ -160,6 +160,38 @@ DEFINE_EVENT(softirq, softirq_raise,
>  	TP_ARGS(vec_nr)
>  );
>  
> +TRACE_EVENT(tasklet_entry,
> +
> +	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)
> +);
> +TRACE_EVENT(tasklet_exit,
> +
> +	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)

This needs an acked-by from Thomas, but regardless, the above two trace
events are identical. You need to have a DECLARE_EVENT_CLASS() followed by
two DEFINE_EVENT()s, otherwise you are wasting memory.

-- Steve


> +);
>  #endif /*  _TRACE_IRQ_H */
>  
>  /* This part must be outside protection */
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index 41f470929e99..b3bce2b3b655 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;

Re: [PATCH v1] softirq: Add tracepoint for tasklet_entry/exit

[Junwen Wu]

From: Steven Rostedt <rostedt@goodmis.org>

>> +
>> +	TP_printk("function=%ps", __entry->func)

>This needs an acked-by from Thomas, but regardless, the above two trace
>events are identical. You need to have a DECLARE_EVENT_CLASS() followed by
>two DEFINE_EVENT()s, otherwise you are wasting memory.

I have use DECLARE_EVENT_CLASS() define use tracepoint,Steve.
Thomas, can you give me acked-by,here is patch v2.


From 68d2298372018ec90c8587d5421a0e1a3c9f879f Mon Sep 17 00:00:00 2001
From: Junwen Wu <wudaemon@163.com>
Date: Sun, 8 May 2022 15:29:56 +0000
Subject: [PATCH v2] softirq: Add tracepoint for tasklet_entry/exit

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>
---
 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 v1] softirq: Add tracepoint for tasklet_entry/exit

[Steven Rostedt]

On Sat, 28 May 2022 13:54:11 +0000
Junwen Wu <wudaemon@163.com> wrote:

> >From 68d2298372018ec90c8587d5421a0e1a3c9f879f Mon Sep 17 00:00:00 2001  
> From: Junwen Wu <wudaemon@163.com>
> Date: Sun, 8 May 2022 15:29:56 +0000
> Subject: [PATCH v2] softirq: Add tracepoint for tasklet_entry/exit

You should always send a v2 as a separate email starting a new thread.

> 
> 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>
> ---

And reference v1 here, by something like:

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(+)


-- Steve