cyclictest: Ensure that next wakeup time is never in the past

The calculated next wakeup time is already in the past, if the latency
is longer than the interval. Thereby latency is detected that does not
correspond to latency caused by the system but by cyclictest itself.

Force forward the next wakeup time past now.

Signed-off-by: Anna-Maria Gleixner <anna-maria@glx-um.de>
Signed-off-by: John Kacur <jkacur@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
index 38525d4..95bdfc3 100644
--- a/src/cyclictest/cyclictest.c
+++ b/src/cyclictest/cyclictest.c
@@ -369,6 +369,12 @@ static inline void tsnorm(struct timespec *ts)
 	}
 }
 
+static inline int tsgreater(struct timespec *a, struct timespec *b)
+{
+	return ((a->tv_sec > b->tv_sec) ||
+		(a->tv_sec == b->tv_sec && a->tv_nsec > b->tv_nsec));
+}
+
 static inline int64_t calcdiff(struct timespec t1, struct timespec t2)
 {
 	int64_t diff;
@@ -949,6 +955,12 @@ void *timerthread(void *param)
 		}
 		tsnorm(&next);
 
+		while (tsgreater(&now, &next)) {
+			next.tv_sec += interval.tv_sec;
+			next.tv_nsec += interval.tv_nsec;
+			tsnorm(&next);
+		}
+
 		if (par->max_cycles && par->max_cycles == stat->cycles)
 			break;
 	}