Bug 1793880 - Unreliable RTC synchronization (11-minute mode) [NEEDINFO]
Summary: Unreliable RTC synchronization (11-minute mode)
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: kernel
Version: 8.1
Hardware: Unspecified
OS: Unspecified
Target Milestone: rc
: 8.0
Assignee: Phil Auld
QA Contact: Qiao Zhao
Depends On:
TreeView+ depends on / blocked
Reported: 2020-01-22 08:07 UTC by Miroslav Lichvar
Modified: 2022-10-17 15:24 UTC (History)
20 users (show)

Fixed In Version: kernel-4.18.0-302.1.el8
Doc Type: No Doc Update
Doc Text:
Clone Of:
: 2135417 (view as bug list)
Last Closed: 2021-11-09 18:56:34 UTC
Type: Bug
Target Upstream Version:
pauld: needinfo? (shtiwari)

Attachments (Terms of Use)

System ID Private Priority Status Summary Last Updated
Gitlab redhat/rhel/src/kernel rhel-8 merge_requests 158 0 None None None 2021-03-12 14:20:54 UTC
Red Hat Issue Tracker CEECBA-5927 0 None None None 2021-11-19 01:09:56 UTC
Red Hat Knowledge Base (Solution) 5017611 0 None None None 2020-11-05 08:51:40 UTC
Red Hat Product Errata RHSA-2021:4356 0 None None None 2021-11-09 18:57:13 UTC

Description Miroslav Lichvar 2020-01-22 08:07:05 UTC
Description of problem:
The kernel doesn't seem to synchronize the RTC to the system clock reliably. It should normally set the RTC about every 11 minutes, but it may take a very long time (hours, days, or possibly never) for the update to actually happen. The problem seems to be in inaccurate scheduling of the update. This was observed with upstream kernels and also RHEL kernels.

An upstream report:

Version-Release number of selected component (if applicable):

How reproducible:
Often, but not always.

Steps to Reproduce:
1. start chronyd with rtcsync in chrony.conf (that is the default)
2. chronyc waitsync
3. hwclock --set --date '10 sec'
4. wait >11 minutes
5. run timedatectl and compare "Local time" with "RTC time"

Actual results:
RTC time off by about 10 seconds

Expected results:
RTC time within <1 second of the Local time

Additional info:

Comment 12 Miroslav Lichvar 2020-12-14 09:32:26 UTC
After some discussion, a different fix was prepared (using a hrtimer) and is waiting to be merged:

Comment 22 kernel-workflow-bot 2021-03-12 22:42:27 UTC
The following Merge Request has pipeline job artifacts available:

Title: [RHEL8.5] Fix RTC synchronization
MR: https://gitlab.com/redhat/rhel/src/kernel/rhel-8/-/merge_requests/158
Pipeline: https://gitlab.com/redhat/rhel/src/kernel/rhel-8/-/pipelines/269596926

This Repo URL is *not* accessible from a web browser! It only functions as a dnf or yum baseurl.
Repo URL: https://s3.upshift.redhat.com/DH-PROD-CKI/internal/269596973/$basearch/4.18.0-296.el8.test.$basearch

Job: https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-internal-contributors/-/jobs/1093420022
Gitlab browser: https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-internal-contributors/-/jobs/1093420022/artifacts/browse/artifacts/repo/4.18.0-296.el8.test.s390x/
Current automated test status: success

Job: https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-internal-contributors/-/jobs/1093420019
Gitlab browser: https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-internal-contributors/-/jobs/1093420019/artifacts/browse/artifacts/repo/4.18.0-296.el8.test.ppc64le/
Current automated test status: success

Job: https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-internal-contributors/-/jobs/1093420018
Gitlab browser: https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-internal-contributors/-/jobs/1093420018/artifacts/browse/artifacts/repo/4.18.0-296.el8.test.aarch64/
Current automated test status: success

Job: https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-internal-contributors/-/jobs/1093420017
Gitlab browser: https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-internal-contributors/-/jobs/1093420017/artifacts/browse/artifacts/repo/4.18.0-296.el8.test.x86_64/
Current automated test status: success

Comment 36 errata-xmlrpc 2021-11-09 18:56:34 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: kernel security, bug fix, and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.


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