On Mon, Apr 20, 2009 at 11:36 PM, Mulyadi Santosa
<mulyadi.santosa@xxxxxxxxx> wrote:
> On Mon, Apr 20, 2009 at 1:03 PM, Lal <learner.kernel@xxxxxxxxx> wrote:
>> I have a Linux system, running a couple of third party kernel modules.
>> The functionality seems all right except a rare case where kernel
>> timers stop expiring. When the system reaches this state, everything
>> works fine except the functionalities depending upon kernel timers.
>> For example:
>>
>> - "sleep 3" on shell never returns
>> - telnet <to some unreachable host> never returns
>> - sample kernel module registers timer using add_timer. But timer never expires
>>
>> It appears to me that one of third party kernel module is causing
>> this. Before I look into the source code, can someone give some hints
>> about possible reasons where kernel timers may stop working
>> (expiring).
>
> let's see...I hope it's not the scheduler tick that is not
> working..because if it does, surely it will affect process' time slice
> expiration. But since now expiration relies on hrtimer (HPET to be
> exact), things might go differently...
>
>
> or maybe something is wrong with the way bottom halves are
> handled...in this case it could be ksoftirqd or do_softirq().
>
> Uhm....could it be because jiffies are not incremented correctly?
> well, not the expert here...i am just trying to dump the possibilities
> in mind.
>
> regards,
>
> Mulyadi.
>
jiffies is increasing properly (I verified using a test module).
The system is running kernel 2.4.21
I suspect some buggy timeout handler function is not returning, that
has stopped other timers to expire . But is there a way to confirm
this?
Following is code snippet from run_timer_list in timer.c file. When
timer is expired, corresponding timeout handler is invoked (call to fn
in below code). If fn does not return, then I guess no further timer
can expire.
if (curr != head) {
struct timer_list *timer;
void (*fn)(unsigned long);
unsigned long data;
timer = list_entry(curr, struct timer_list, list);
fn = timer->function;
data= timer->data;
detach_timer(timer);
timer->list.next = timer->list.prev = NULL;
timer_enter(timer);
spin_unlock_irq(&timerlist_lock);
fn(data);
spin_lock_irq(&timerlist_lock);
timer_exit();
goto repeat;
Any comments would be appreciated.
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