add_timer crashes the kernel,Why?

[lijin liu]

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.

It just works!

But why the add_timer crash the kernel?