hrtimer integration: properly trace late-added timers

When tasks add timers that have already expired (e.g., when preempted
during schedule_hrtimeout), we should not use the expriration time as
the reference time point, but rather the time when the timer was added
(the delay then includes activation of ksoftirqd, etc.).

1 files changed, 6 insertions, 1 deletions

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 70aebc72dfb8..a6d5b061ee67 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1518,12 +1518,17 @@ static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)
         t->task = NULL;
         if (task)
         {
+#ifdef CONFIG_SCHED_OVERHEAD_TRACE
                 if (is_realtime(task))
                 {
                         ktime_t expires = hrtimer_get_expires(timer);
-                        lt_t intended_release = ktime_to_ns(expires);
+                        /* Fix up timers that were added past their due date;
+                         * that's not really release latency. */
+                        lt_t intended_release = max(expires.tv64,
+                                                    timer->when_added.tv64);
                         TS_RELEASE_LATENCY(intended_release);
                 }
+#endif
                 TS_RELEASE_START;
                 wake_up_process(task);
                 TS_RELEASE_END;