Miroslav Lichvar 2ed88c31c7 sys_generic: damp slew oscillation due to delayed stop ...

If the computer is overloaded so much that chronyd cannot stop a slew
within one second of the scheduled end and the actual duration is more
than doubled (2 seconds with the minimum duration of 1 second), the
overshoot will be larger than the intended correction. If these
conditions persist, the oscillation will grow up to the maximum offset
allowed by maxslewrate and the delay in stopping.

Monitor the excess duration as an exponentially decaying maximum value
and don't allow any slews shorter than 5 times the value to damp the
oscillation. Ignore delays longer than 100 seconds, assuming they have a
different cause (e.g. the system was suspended and resumed) and are
already handled in the scheduler by triggering cancellation of the
ongoing slew.

This should also make it safer to shorten the minimum duration if
needed.

Reported-by: Daniel Franke <dff@amazon.com>

2022-06-15 17:42:49 +02:00

14 KiB

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