From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D1A3F3B38A6 for ; Thu, 30 Apr 2026 12:03:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777550605; cv=none; b=csI5LT9fL0o3m9bUusC42AfTQNADHnNhceND899w9/03UPjWfs+YPyCcNIIBH5QD/B0L3AFu99xUXpO5r+NjYODtegBhsJGQ9+aL+IwVmEMudEshMx9mowj8tkaqxjXo/Y11MycPV1enK6AUnb5Y6SZT5Gt1E9MY+kOGyh1dxqQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777550605; c=relaxed/simple; bh=duJWKLbfqTL4D1zNPPk5QveBYRxoms7eL2nTGNWcLqY=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=Z0XR+2CZH1qeb4R+gZIasYRYZ9eLg5fK5V7D+s1JCUiOaRefnwMUYxiF9dcpLcqpFhVrQ98OlCscQAzk6IHT9xflf1iHbNP+1XoKIZdggFZHy0M5cRexrMb2WyzZKs15FFcJPuh/iq//ui6zNmG1+eOgZlyN6ugXZ1a95oaqWm8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--wakel.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=eoIk2JN9; arc=none smtp.client-ip=209.85.210.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--wakel.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="eoIk2JN9" Received: by mail-pf1-f202.google.com with SMTP id d2e1a72fcca58-82fbceb0181so639105b3a.3 for ; Thu, 30 Apr 2026 05:03:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1777550603; x=1778155403; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=PvMj/MkllnjgvE6Y7N3WHrJDvNHvsjKi1M8BHUaGO3o=; b=eoIk2JN9G0lyeyRKP9OQ4Tmjgi/XHJFUFEOiGH/rT+vjWi0kjVgOWKb+qY6I1IB7Fb wxNDv9uZL2Uyy78H22fmrEGDpoyoSt5q0d9mwdFCgHy0hvzfnRZ8PeWDzwdEyGoYRq7Y TxMjd4699QKuOgsNckmLFHI5UEdtlx9J7b486gPtkR+REwrcoIY975S4/EPvFyskH+ZF 88SbgwcJy1UVi/ySM5O9MP6pkU1M4ik5qllBKDgq52rjSS3L0KAfPaMuajVEk2Aj42no in24wqfNSh1TOb/MuD2XFSyBxD64T1MlXjPpdASIx+8GVXK/ds13e40kzzg1QMku7hig +Fgw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777550603; x=1778155403; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=PvMj/MkllnjgvE6Y7N3WHrJDvNHvsjKi1M8BHUaGO3o=; b=TOP4PQyvlHtLBsXgS8bGyLeEuPiTEsb72DDXP4q5PDd98WGstLbUvBVsNrP6I0PJ8N T8aYkqR9uTiZ1q8e/lSSc9YrwUEKIM3TUDlJBwLVlSPEOWEHiqI8SBelQYjPUIh8XIgW 9n72VZIaUTyVUTnNp6TqoAsXrVrSsXnIblWScy3yHgfsbvWjYRipbAx6K8P7JZZOsv3O ZlCjC9XJ+LxNMsQoPBWJqzXTgza95LV60yuhcZepfkJ1DySZmL1cWd5cxHzrQmH4oC16 MHDgA+xPz5UOVUz536f5QkdOYWOOXALjlk87c76cN/mA0fdi0JpjYJj/ajOpIpg8W+YP WvlA== X-Forwarded-Encrypted: i=1; AFNElJ9yUjB1T12uxDwJLeFMU2NcjvdupzOPURMaKxZVzOEtU4YFMst7SDRB/P5F//X11/35Zfe0ZpEfaJ6Xx2g=@vger.kernel.org X-Gm-Message-State: AOJu0YxrhqUpuZgahxb19B5MdmV9KKLxgBagWo5/uNgo4eavGv2mrwIM rHohWxq8hErVluax7taQQ/FYBZUaL7Pe86UXgRBtlfN6NKKtw0q1510JLHr7PRgZI7bbH6z7JYj pJw== X-Received: from pfbgx2.prod.google.com ([2002:a05:6a00:1e02:b0:82f:b322:30fb]) (user=wakel job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:340a:b0:82f:1973:4b96 with SMTP id d2e1a72fcca58-834fdcdef18mr2884609b3a.26.1777550602832; Thu, 30 Apr 2026 05:03:22 -0700 (PDT) Date: Thu, 30 Apr 2026 20:03:13 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.54.0.545.g6539524ca2-goog Message-ID: <20260430120313.4078185-1-wakel@google.com> Subject: [PATCH] selftests: rtc: fix flaky date_read_loop test From: Wake Liu To: Alexandre Belloni , Shuah Khan Cc: linux-rtc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Wake Liu Content-Type: text/plain; charset="UTF-8" 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 --- 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