Re: repeat a function after fixed time period

[linux-os <linux-os@analogic.com>]

On Wed, 23 Mar 2005, sounak chakraborty wrote:

> dear sir
> i want to call my own function inside the kernel
> after a fixed interval(i.e some kind of timer)
> how to do that which function i have to use to
> repeat the function
>
> anather way is that making my own system call
> which calls my function and
> this sytem call is being access by a user program
> which calls it after a fixed inter val of time
> will this be correct
> thanks
> sounak

This kernel code should do just fine.



struct INFO {
    struct timer_list timer;            // For test timer
    atomic_t running;                   // Timer is running
    };

//-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//
//   This stops the timer. This must NOT be called with a spin-lock
//   held.
//
static void stop_timer()
{
    if(atomic_read(&info->running))
    {
        atomic_dec(&info->running);
        if(info->timer.function)
            del_timer(&info->timer);
    }
}
//-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//
//    This starts the timer. This must NOT be called with a spin-lock
//    held.
//
static void start_timer(void)
{
    if(!atomic_read(&info->running))
    {
        atomic_inc(&info->running);
        init_timer(&info->timer);
        info->timer.expires = jiffies + HZ;
        info->timer.data = 0;
        info->timer.function = test_timer;
        add_timer(&info->timer);
    }
}
//-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//
//   This is the code that executes at a timer-interval.
//
static void test_timer(unsigned long data)
{
    info->timer.expires = jiffies + HZ;         // New expiration time
    if(atomic_read(&info->running))             // If it's still running
    {
        code_to_execute_every_timer_interval();
        add_timer(&info->timer);                // Into timer-queue again
    }
}
//-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=


Cheers,
Dick Johnson
Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips).
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