[LTP] [PATCH] timer_getoverrun/2-3: increase tolerance for overshoot

[Jan Stancek]

Joerg reports that test fails on systems with low timer precision (qemu-arm64,
4ms timer precision) due to way we calculate maximum number of overruns.
If the expected overruns is less than 200, there is no tollerance.

Allow up to ~50ms of extra overruns.

Reported-by: Joerg Vehlow <joerg.vehlow@aox-tech.de>
Acked-by: Joerg Vehlow <joerg.vehlow@aox-tech.de>
Signed-off-by: Jan Stancek <jstancek@redhat.com>
---
 .../conformance/interfaces/timer_getoverrun/2-3.c             | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/testcases/open_posix_testsuite/conformance/interfaces/timer_getoverrun/2-3.c b/testcases/open_posix_testsuite/conformance/interfaces/timer_getoverrun/2-3.c
index 96b7d01e6ffe..66f8b583a5a6 100644
--- a/testcases/open_posix_testsuite/conformance/interfaces/timer_getoverrun/2-3.c
+++ b/testcases/open_posix_testsuite/conformance/interfaces/timer_getoverrun/2-3.c
@@ -94,11 +94,17 @@ int main(void)
 
 	valuensec = tsres.tv_nsec;
 	intervalnsec = 2 * valuensec;
-	//expectedoverruns = (1000000000 - valuensec) / intervalnsec;
 	expectedoverruns = 1000000000 / intervalnsec - 1;
 
+	/*
+	 * waking up from sleep isn't instant, we can overshoot.
+	 * Allow up to ~50ms worth of extra overruns.
+	 */
+	fudge = 50000000 / intervalnsec + 1;
+
 	printf("value = %d sec, interval = %d nsec, "
-	       "expected overruns = %d\n", 1, intervalnsec, expectedoverruns);
+	       "expected overruns = %d, fudge = %d\n", 1,
+	       intervalnsec, expectedoverruns, fudge);
 
 	its.it_interval.tv_sec = 0;
 	its.it_interval.tv_nsec = intervalnsec;
@@ -146,7 +152,6 @@ int main(void)
 	 * extra expiries after the nanosleep completes so do
 	 * a range check.
 	 */
-	fudge = expectedoverruns / 100;
 	if (overruns >= expectedoverruns && overruns < expectedoverruns + fudge) {
 		printf("Test PASSED\n");
 		return PTS_PASS;
-- 
1.8.3.1