On 12/20/2010 2:08 AM, Mulyadi Santosa wrote:
Hi :)
On Mon, Dec 20, 2010 at 15:27, lijin liu<llj098@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
I believe add_timer just prevents creating duplicate timers from the same struct. I was actually thinking I had the same problem with timer code (following essential linux device drivers). But the issue was removing a module with an active timer will cause a crash. Here is what I ended up with, a silly sample timer that chains itself 3 times. It might be useful to OP: http://pastebin.com/v4rr3t50 -- -Dexter Haslem