LinuxQuestions.org - TRACEPOINTs in Linux Kernel

Hi,

I am trying to learn module development in Linux Kernel and I wanted to know how to use a tracepoint already defined in the linux kernel :
http://kernel.org/doc/htmldocs/trace...-complete.html

The tracepoint I am referring to is :
trace_block_bio_complete();

As per the documentation it says that trace_block_bio_complete() is called when the Block operation is completed :
This tracepoint indicates there is no further work to do on this block IO operation bio.

But when I write a KERNEL Module for the same, its not working. Here is the code :

Code:



#include <linux/init.h>

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/blkdev.h>

#include <linux/blktrace_api.h>

#include <linux/percpu.h>

#include <linux/bio.h>

#include <linux/tracepoint.h>



MODULE_LICENSE("Dual BSD/GPL");



int mymod_count = 0;



static void mymod_trace_bio_complete(struct request_queue *q, struct bio *bio)

{

        if(mymod_count < 10){

                printk(KERN_INFO "%d ... \n", mymod_count);

        }

        mymod_count++;

}



static int mymod_init(void) {

        

        int ret;



        printk("<1> Starting mymod kernel module ... \n");



        ret = register_trace_block_bio_complete(mymod_trace_bio_complete);

        WARN_ON(ret);



}



static void mymod_exit(void) {

  

        printk("<1> Stopping mymod kernel module ... \n");



        unregister_trace_block_bio_complete(mymod_trace_bio_complete);

  

}



module_init(mymod_init);

module_exit(mymod_exit);

Please let me know what I am doing wrong. Also I dont know if there is any dedicated forum or mailing list where I can ask questions about kernel development.

Looking forward to any input :)