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From 9851deb86ef257a98d7433280161d8ca685aa669 Mon Sep 17 00:00:00 2001
From: Li Wang <liwang@redhat.com>
Date: Tue, 29 Mar 2022 13:03:51 +0800
Subject: [PATCH] clock_gettime04: set threshold based on the clock resolution
This is to get rid of the intermittent failures in clock_gettime04,
which are likely caused by different clock tick rates on platforms.
Here give two thresholds (in milliseconds) for comparison, one for
COARSE clock and one for the rest.
Error log:
clock_gettime04.c:163: TFAIL: CLOCK_REALTIME_COARSE(syscall with old kernel spec):
Difference between successive readings greater than 5 ms (1): 10
clock_gettime04.c:163: TFAIL: CLOCK_MONOTONIC_COARSE(vDSO with old kernel spec):
Difference between successive readings greater than 5 ms (2): 10
From Waiman Long:
That failure happens for CLOCK_REALTIME_COARSE which is a faster but less
precise version of CLOCK_REALTIME. The time resolution is actually a clock
tick. Since arm64 has a HZ rate of 100. That means each tick is 10ms. So a
CLOCK_REALTIME_COARSE threshold of 5ms is probably not enough. I would say
in the case of CLOCK_REALTIME_COARSE, we have to increase the threshold based
on the clock tick rate of the system. This is more a test failure than is
an inherent problem in the kernel.
Fixes #898
Upstream-Status: Backport
[https://github.com/linux-test-project/ltp/commit/9851deb86ef257a98d7433280161d8ca685aa669]
Reported-by: Eirik Fuller <efuller@redhat.com>
Signed-off-by: Li Wang <liwang@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Xiangyu Chen <xiangyu.chen@windriver.com>
---
.../syscalls/clock_gettime/clock_gettime04.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/testcases/kernel/syscalls/clock_gettime/clock_gettime04.c b/testcases/kernel/syscalls/clock_gettime/clock_gettime04.c
index a8d2c5b38..c279da79e 100644
--- a/testcases/kernel/syscalls/clock_gettime/clock_gettime04.c
+++ b/testcases/kernel/syscalls/clock_gettime/clock_gettime04.c
@@ -35,7 +35,7 @@ clockid_t clks[] = {
};
static gettime_t ptr_vdso_gettime, ptr_vdso_gettime64;
-static long long delta = 5;
+static long long delta, precise_delta, coarse_delta;
static inline int do_vdso_gettime(gettime_t vdso, clockid_t clk_id, void *ts)
{
@@ -92,9 +92,18 @@ static struct time64_variants variants[] = {
static void setup(void)
{
+ struct timespec res;
+
+ clock_getres(CLOCK_REALTIME, &res);
+ precise_delta = 5 + res.tv_nsec / 1000000;
+
+ clock_getres(CLOCK_REALTIME_COARSE, &res);
+ coarse_delta = 5 + res.tv_nsec / 1000000;
+
if (tst_is_virt(VIRT_ANY)) {
tst_res(TINFO, "Running in a virtual machine, multiply the delta by 10.");
- delta *= 10;
+ precise_delta *= 10;
+ coarse_delta *= 10;
}
find_clock_gettime_vdso(&ptr_vdso_gettime, &ptr_vdso_gettime64);
@@ -108,6 +117,11 @@ static void run(unsigned int i)
int count = 10000, ret;
unsigned int j;
+ if (clks[i] == CLOCK_REALTIME_COARSE || clks[i] == CLOCK_MONOTONIC_COARSE)
+ delta = coarse_delta;
+ else
+ delta = precise_delta;
+
do {
for (j = 0; j < ARRAY_SIZE(variants); j++) {
/* Refresh time in start */
--
2.34.1
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