Helge,
On Sat, 26 Dec 2015, Helge Deller wrote:
> I see a strange behavior on the parisc platform, for which I'm not sure if
> it's intended or if there is a bug somewhere.
> The program calls timerfd_settime() and sets a timer (e.g. sec=0, nsec=100000000).
> Directly after setting the timer it calls timerfd_gettime() and receives
> (sec=0, nsec=103914413).
> The second nsec is higher than the initial nsec value which was set.
>
> Does timerfd_settime() maybe tries to add the initial time it takes to start
> the timer?
>
> Any idea or hint?
Yes. This is a fallout from the power aware batching magic. Interesting that
nobody noticed this within 7 years.
Does the patch below fix your issue?
Thanks,
tglx
8<----------------
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 76dd4f0da5ca..0f4a3e8734f1 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -268,7 +268,7 @@ static inline s64 hrtimer_get_expires_ns(const struct hrtimer *timer)
static inline ktime_t hrtimer_expires_remaining(const struct hrtimer *timer)
{
- return ktime_sub(timer->node.expires, timer->base->get_time());
+ return ktime_sub(timer->_softexpires, timer->base->get_time());
}
static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
--
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