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SubjectLatency histogram broken after "hrtimer: Set expiry time before switch_hrtimer_base()"
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Date
In an rt-kernel with CONFIG_MISSED_TIMER_OFFSETS_HIST enabled,
__hrtimer_start_range_ns() now crashes, as new_base is not assigned
before it is used.

I'm not sure how this should be fixed; is it:

--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1108,7 +1108,7 @@ int __hrtimer_start_range_ns(struct hrti

#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
{
- ktime_t now = new_base->get_time();
+ ktime_t now = base->get_time();

if (ktime_to_ns(tim) < ktime_to_ns(now))
timer->praecox = now;
--- END ---
or:

--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1106,6 +1106,11 @@ int __hrtimer_start_range_ns(struct hrti
#endif
}

+ hrtimer_set_expires_range_ns(timer, tim, delta_ns);
+
+ /* Switch the timer base, if necessary: */
+ new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
+
#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
{
ktime_t now = new_base->get_time();
@@ -1117,11 +1122,6 @@ int __hrtimer_start_range_ns(struct hrti
}
#endif

- hrtimer_set_expires_range_ns(timer, tim, delta_ns);
-
- /* Switch the timer base, if necessary: */
- new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
-
timer_stats_hrtimer_set_start_info(timer);

leftmost = enqueue_hrtimer(timer, new_base);
--- END ---
or something else?

Ben.

--
Ben Hutchings
73.46% of all statistics are made up.
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