The test case rtc.date_read_loop in rtctest.c fails intermittently because it checks that the RTC time does not advance by more than 1 second per loop iteration. However, the loop sleeps for 11ms via nanosleep(), and if the test thread is descheduled by the OS scheduler (e.g., under heavy system load in a VM), more than 1 second can elapse between consecutive RTC reads. This causes the next RTC time read to be 2 or more seconds ahead of the previous read, triggering a test assertion failure.
To make the test more resilient against OS scheduling delays, measure the real elapsed time between iterations using a monotonic clock (clock_gettime(CLOCK_MONOTONIC)), and compute the actual number of seconds elapsed (delta_s) between consecutive RTC reads. Then dynamically adjust the assertion to: ASSERT_GE(prev_rtc_read + delta_s + 1, rtc_read); Signed-off-by: Wake Liu <[email protected]> --- tools/testing/selftests/rtc/rtctest.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/rtc/rtctest.c b/tools/testing/selftests/rtc/rtctest.c index 8047d9879039..54eb5c255a45 100644 --- a/tools/testing/selftests/rtc/rtctest.c +++ b/tools/testing/selftests/rtc/rtctest.c @@ -116,6 +116,7 @@ TEST_F_TIMEOUT(rtc, date_read_loop, READ_LOOP_DURATION_SEC + 2) { long iter_count = 0; struct rtc_time rtc_tm; time_t start_rtc_read, prev_rtc_read; + struct timespec prev_mono, cur_mono; if (self->fd == -1 && errno == ENOENT) SKIP(return, "Skipping test since %s does not exist", rtc_file); @@ -126,25 +127,31 @@ TEST_F_TIMEOUT(rtc, date_read_loop, READ_LOOP_DURATION_SEC + 2) { rc = ioctl(self->fd, RTC_RD_TIME, &rtc_tm); ASSERT_NE(-1, rc); + clock_gettime(CLOCK_MONOTONIC, &prev_mono); start_rtc_read = rtc_time_to_timestamp(&rtc_tm); prev_rtc_read = start_rtc_read; do { time_t rtc_read; + time_t delta_s = 0; rc = ioctl(self->fd, RTC_RD_TIME, &rtc_tm); ASSERT_NE(-1, rc); + clock_gettime(CLOCK_MONOTONIC, &cur_mono); rtc_read = rtc_time_to_timestamp(&rtc_tm); + delta_s = cur_mono.tv_sec - prev_mono.tv_sec; + /* Time should not go backwards */ ASSERT_LE(prev_rtc_read, rtc_read); - /* Time should not increase more then 1s at a time */ - ASSERT_GE(prev_rtc_read + 1, rtc_read); + /* Time should not increase more then elapsed time + 1s */ + ASSERT_GE(prev_rtc_read + delta_s + 1, rtc_read); /* Sleep 11ms to avoid killing / overheating the RTC */ nanosleep_with_retries(READ_LOOP_SLEEP_MS * 1000000); prev_rtc_read = rtc_read; + prev_mono = cur_mono; iter_count++; } while (prev_rtc_read <= start_rtc_read + READ_LOOP_DURATION_SEC); -- 2.54.0.545.g6539524ca2-goog
