Linux-kernel debug printouts?

Question

Is there a better way to debug printouts in the Linux kernel?

Right now littering the code with:

printk(KERN_DBG "%s:%d - %s() <message>", __FILE__, __LINE__, __FUNCTION__ ); 

Which isn't very clean.

There ought to be a way for the whole row to be #ifdef:ed in some nice way.

Cressler

maybe you can take a look at this question – Dupuy

Kevin: Thanks, but it's not quite what I'm looking for. I'm looking a way to deal with actual debug printouts, not how to run a debugger. – Cressler

Answer 1

Use

/* At the top of the file, before any includes */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/printk.h>

/* in code... */
pr_devel("foobar happened\n");

as a basis (the standard practice). You can then add __FILE__ or __LINE__ to the pr_fmt definition if you need.

Trevar

Do I understand this bit correctly? pr_<arg>(<args>) <my modules name> ":" <printk args> Would that work? Don't I have to invoke prinkt() aswell? – Cressler

You do not need to repeat the module name at all. pr_devel calls printk. To spell it out, #define pr_fmt(fmt) KBUILD_MODNAME ":" __FILE__ ":" __LINE__ ": " fmt, plus pr_devel("stuff and %p\n", somepointer). – Trevar

I am using the same syntax but I am getting an error: error: expected ‘)’ before numeric constant I have this in my code: #define pr_fmt(fmt) KBUILD_MODNAME ":" __FILE__ ":" __LINE__ ": " fmt (before any #include) and in the code pr_devel("XXX\n"); – Trombone

@brokenfoot: I know this has been very old, but I stumbled into the same problem today and I have found a solution for having all the file name, function and line number: #define pr_fmt(fmt) KBUILD_MODNAME ": " __FILE__ ", function %s, line %d: " fmt, __func__, __LINE__ Hope this will help any googlers like me in the future. – Aylesbury

Have a look here on how to fix macro: #36241933 – Stets

Answer 2

If this is for quick debugging, just printk() works well.

If this is for debugging in more production situation, maybe use pr_debug(), so messages can be enabled at runtime.

Regardless, ("%s: xxx", func) is usually enough. These filenames and line numbers will become annoying very soon. This is also why you haven't found any "standard" solution -- because there is none.

Sung