Bug 1910125

Description of problem:
Hardware clock is not being kept synchronized.

Version-Release number of selected component (if applicable):
chrony-3.4-1.el7.x86_64

How reproducible:
Consistently

Steps to Reproduce:
1. Ensure chrony is running with the "rtcsync" option enabled in /etc/chrony.conf (as it is by default).
2. Run timedatectl; compare the system time with the RTC time.  (If necessary, manually set the RTC time a few seconds fast or slow, and wait: "rtcsync" is supposed to cause the kernel to correct the error within 11 minutes.)

Actual results:
RTC may drift significantly from the system time, notwithstanding the note in Chapter 3 of the System Administrators Guide that "the kernel automatically synchronizes the hardware clock to the system clock every 11 minutes."

Expected results:
RTC should not drift significantly from the system time when chrony is running with rtcsync enabled.

Additional info:
Red Hat Enterprise Linux 7/8 kernels appear to be built without the CONFIG_RTC_SYSTOHC option, which appears to be the mechanism which is supposed to keep the hardware clock synchronized with the system time when NTP is active.

If CONFIG_RTC_SYSTOHC is not going to be set in shipped kernels, a different mechanism should be used to keep the hardware clock synchronized (e.g., running hwclock during shutdown as Red Hat Enterprise Linux 6 did), and/or the documentation should be corrected to indicate that chrony's rtcsync directive has no effect when using default Red Hat Enterprise Linux kernels; it may or may not be prudent to change the chrony configuration to use rtcfile or a similar mechanism by default to manage hardware clock drift instead.

Similar issues may apply to the ntp package, and also to Red Hat Enterprise Linux 8.