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Old 04-28-2012, 11:11 PM   #1
vzxen
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Registered: Jul 2010
Posts: 126

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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
 
Old 04-30-2012, 06:49 AM   #2
vzxen
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Registered: Jul 2010
Posts: 126

Original Poster
Rep: Reputation: 4
Can anyone guide me to any forum which is dedicated to linux kernel programming.
I would really appreciate any help on the problem I face with the kernel module programming.
 
  


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