add_timer crashes the kernel,Why?

[Mulyadi Santosa]

Hi :)

On Mon, Dec 20, 2010 at 15:27, lijin liu <llj098 at gmail.com> wrote:
> Hello everyone!
>
> I want to use the timer in my kernel module. I read the book  _Linux
> kernel development 3rd version_  and LDD 3rd version.
>
> Both the two books tell me write the code like this:
>
> struct timer_list my_timer;
> init_timer(&my_timer);
>
> my_timer.expires = jiffies + wait;
> my_timer.data = 0;
> my_timer.function=my_function;
>
> //active the timer:
> add_timer(&timer);
>
>
> When I insmod the module, the kernel crashed, and when I change my
> code to *mod_timer* rather than add_timer.

Hmmm, from http://lxr.linux.no/linux+v2.6.36/kernel/timer.c#L864, it reads:
void add_timer(struct timer_list *timer)
{
        BUG_ON(timer_pending(timer));
        mod_timer(timer, timer->expires);
}

thus, IMHO the error happened because there is other timer pending...
somehow it is forbidden to add timer when other are still in queue in
latest kernel

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com