behaviour of dynamic (kernel) timer

bizoo · 01-26-2010, 05:36 AM

HI
My system: Ubuntu 2.6.31. Language C, compiler: gcc

I am running dynamic timer as a kernel module and my issue is that the once the timer overflows , the program finishes. On the other hand i have forced to arm the timer again because of a while loop but the timer never is started again.
i am targetting a periodic timer but it runs once and thats it.

any ideas?
thx

Code:

#include <asm/param.h>
#include <linux/sched.h>
#include "ktimer.h"
struct timer_list mtimer;
int actual_module(void);
void handler(unsigned long z);

int actual_module()
{
int k=0,x=0;
init_timer(&mtimer);	
mtimer.function=handler;
while(k<2){
x=mod_timer(&mtimer, jiffies +2*HZ ) ;
schedule();
k++;
}

//timeout=expire-jiffies;

return 0;
}


void handler(unsigned long z)
{
printk("the timer overflows  \n");
return;
}




static int __init ktimer_init(void)
{
 int err = 0;
 printk(KERN_INFO  "dynamic timer module init\n");
 err= actual_module();
 if(err != 0) 
 {
 return err;
 }
 return 0;	
}

static void __exit ktimer_exit(void)
{
del_singleshot_timer_sync(&mtimer);
return;
}


module_init(ktimer_init);
module_exit(ktimer_exit);

shishir · 01-28-2010, 12:10 AM

you might want to move this statement inside the timer callback. After all, when you say periodic, you don't want the same timer to be initialized twice, as your code does or tries to do(kernel actually initializes it only once), but to be called every 2 secs. For it to be called every 2 secs, you would need the timer callback to invoke mod_timer every time it runs.

Code:

#include <asm/param.h>
#include <linux/sched.h>
#include "ktimer.h"
struct timer_list mtimer;
int actual_module(void);
void handler(unsigned long z);

int actual_module()
{
int k=0,x=0;
init_timer(&mtimer);	
mtimer.function=handler;

x=mod_timer(&mtimer, jiffies +2*HZ ) ;
schedule();
k++;


//timeout=expire-jiffies;

return 0;
}


void handler(unsigned long z)
{
printk("the timer overflows  \n");
mod_timer(&mtimer, jiffies +2*HZ ) ;
return;
}




static int __init ktimer_init(void)
{
 int err = 0;
 printk(KERN_INFO  "dynamic timer module init\n");
 err= actual_module();
 if(err != 0) 
 {
 return err;
 }
 return 0;	
}

static void __exit ktimer_exit(void)
{
del_singleshot_timer_sync(&mtimer);
return;
}


module_init(ktimer_init);
module_exit(ktimer_exit);