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Date:   Sun, 14 Jun 2020 08:05:01 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jim Cromie <jim.cromie@...il.com>
Cc:     jbaron@...mai.com, linux-kernel@...r.kernel.org,
        akpm@...uxfoundation.org, linux@...musvillemoes.dk
Subject: Re: [PATCH v2 23/24] kset-example: add pr_debug()s for easy
 visibility of its operation

On Sat, Jun 13, 2020 at 09:57:37AM -0600, Jim Cromie wrote:
> put pr_debug()s into most functions, to easily see code operate when
> module is loaded and used.
> 
>   #> dmesg -w &
>   #> modprobe kset-example dyndbg=+pfml
>   #> cat /sys/kernel/kset-example/*/*
> ---
>  samples/kobject/kset-example.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/samples/kobject/kset-example.c b/samples/kobject/kset-example.c
> index c8010f126808..27c9b1beec28 100644
> --- a/samples/kobject/kset-example.c
> +++ b/samples/kobject/kset-example.c
> @@ -56,6 +56,7 @@ static ssize_t foo_attr_show(struct kobject *kobj,
>  	struct foo_attribute *attribute;
>  	struct foo_obj *foo;
>  
> +	pr_debug("called");
>  	attribute = to_foo_attr(attr);
>  	foo = to_foo_obj(kobj);
>  
> @@ -76,6 +77,7 @@ static ssize_t foo_attr_store(struct kobject *kobj,
>  	struct foo_attribute *attribute;
>  	struct foo_obj *foo;
>  
> +	pr_debug("called");
>  	attribute = to_foo_attr(attr);
>  	foo = to_foo_obj(kobj);
>  
> @@ -102,6 +104,7 @@ static void foo_release(struct kobject *kobj)
>  {
>  	struct foo_obj *foo;
>  
> +	pr_debug("called");
>  	foo = to_foo_obj(kobj);
>  	kfree(foo);
>  }
> @@ -112,6 +115,7 @@ static void foo_release(struct kobject *kobj)
>  static ssize_t foo_show(struct foo_obj *foo_obj, struct foo_attribute *attr,
>  			char *buf)
>  {
> +	pr_debug("called");
>  	return sprintf(buf, "%d\n", foo_obj->foo);
>  }
>  
> @@ -120,6 +124,7 @@ static ssize_t foo_store(struct foo_obj *foo_obj, struct foo_attribute *attr,
>  {
>  	int ret;
>  
> +	pr_debug("called");
>  	ret = kstrtoint(buf, 10, &foo_obj->foo);
>  	if (ret < 0)
>  		return ret;
> @@ -140,6 +145,7 @@ static ssize_t b_show(struct foo_obj *foo_obj, struct foo_attribute *attr,
>  {
>  	int var;
>  
> +	pr_debug("called");
>  	if (strcmp(attr->attr.name, "baz") == 0)
>  		var = foo_obj->baz;
>  	else
> @@ -152,6 +158,7 @@ static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr,
>  {
>  	int var, ret;
>  
> +	pr_debug("called");
>  	ret = kstrtoint(buf, 10, &var);
>  	if (ret < 0)
>  		return ret;
> @@ -201,6 +208,7 @@ static struct foo_obj *create_foo_obj(const char *name)
>  	struct foo_obj *foo;
>  	int retval;
>  
> +	pr_debug("called");
>  	/* allocate the memory for the whole object */
>  	foo = kzalloc(sizeof(*foo), GFP_KERNEL);
>  	if (!foo)
> @@ -235,11 +243,13 @@ static struct foo_obj *create_foo_obj(const char *name)
>  
>  static void destroy_foo_obj(struct foo_obj *foo)
>  {
> +	pr_debug("called");
>  	kobject_put(&foo->kobj);
>  }
>  
>  static int __init example_init(void)
>  {
> +	pr_debug("called");

Why???  If you want to do something like this, use ftrace, that is what
it is for.

thanks,

greg k-h

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