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SubjectRe: [RFC] [PATCH 1/1] hrtimers: Cache next hrtimer
On Fri, 28 Aug 2009, Ashwin Chaugule wrote:
> Thomas Gleixner wrote:
> Just didn't know the following could have the same effect. (base->offset is
> confusing)

It's simple. We have CLOCK_MONOTONIC and CLOCK_REALTIME. The internal
time base is CLOCK_MONOTONIC. So we use base->offset to convert
CLOCK_REALTIME to CLOCK_MONOTONIC. In case the timer is
CLOCK_MONOTONIC we so the substraction as well, but it simply
subtracts 0 :)

> + /*
> + * Remove the timer from the rbtree and replace the first
> + * entry pointer if necessary.
> + */
> + rb_erase(&timer->node, &base->active);
> +
> + if (base->first != &timer->node)
> + goto out;
> +
> + base->first = rb_next(&timer->node);

Gah. Looking at the patch with an awake brain makes me feel
stupid. Working version below.

Thanks,

tglx
---
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 49da79a..380682b 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -906,19 +906,28 @@ static void __remove_hrtimer(struct hrtimer *timer,
struct hrtimer_clock_base *base,
unsigned long newstate, int reprogram)
{
- if (timer->state & HRTIMER_STATE_ENQUEUED) {
- /*
- * Remove the timer from the rbtree and replace the
- * first entry pointer if necessary.
- */
- if (base->first == &timer->node) {
- base->first = rb_next(&timer->node);
- /* Reprogram the clock event device. if enabled */
- if (reprogram && hrtimer_hres_active())
+ ktime_t expires;
+
+ if (!(timer->state & HRTIMER_STATE_ENQUEUED))
+ goto out;
+
+ /*
+ * Remove the timer from the rbtree and replace the first
+ * entry pointer if necessary.
+ */
+ if (base->first == &timer->node) {
+ base->first = rb_next(&timer->node);
+ /* Reprogram the clock event device. if enabled */
+ if (reprogram && hrtimer_hres_active()) {
+ expires = ktime_sub(hrtimer_get_expires(timer),
+ base->offset);
+ if (base->cpu_base->expires_next.tv64 == expires.tv64)
hrtimer_force_reprogram(base->cpu_base);
}
- rb_erase(&timer->node, &base->active);
}
+
+ rb_erase(&timer->node, &base->active);
+out:
timer->state = newstate;
}


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