hrtimer, is triggered based on softirq mechanism. and it can be
triggered whether interrupt is enabled or disabled - two different
modes.
checkout kernel/hrtimer.c. within u can find the function
enqueue_hrtimer(), which shows how the hrtimer can be enqueued into a
red black tree. so similarly if u want to enumerate all the
hrtimer....use these rb_xxxx API.
and to identify the timer, inside the hrtimer structure
(include/linux/hrtimer.h) there is a field "start_pid" or
"start_comm", which gave info about the pid or process name which
started the timer.
struct hrtimer {
struct rb_node node;
ktime_t _expires;
ktime_t _softexpires;
enum hrtimer_restart (*function)(struct hrtimer *);
struct hrtimer_clock_base *base;
unsigned long state;
struct list_head cb_entry;
#ifdef CONFIG_TIMER_STATS
int start_pid;
void *start_site;
char start_comm[16];
#endif
};
The callback function "function" in the structure above is called when
timer expired. The caller is hrtimer_interrupt(), called by
hrtimer_peek_ahead_timers(), called by run_hrtimer_softirq() etc.
On Thu, Jun 25, 2009 at 5:09 PM, Nicola Manica<[email protected]> wrote:
> Hi, I'm a student that want to study the kernel code.
> I have a simple question:
> If I set an hrtimer, I think that when it expires it raise a timer
> interrupt. What is the sequence of functions called at this point (in a
> recent kernel for example 2.6.29)?
> How I can know which is the timer expired?
> Thanks for the reply, and maybe sorry for the stupid question.
> Nicola
>
--
Regards,
Peter Teoh
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