On 2/12/26 11:09, Peter Wallace wrote:
On Thu, 12 Feb 2026, Bertho Stultiens wrote:
Hi all,
Is there anybody who has a LinuxCNC instance that runs for more than
(multiples of) about 49 days at a time (that is for a 1kHz
servo-thread)?
There is a race condition when a 32-bit heartbeat counter wraps. It
can only be hit every ~49 days within a time window of one
servo-thread period (usually 1ms). So, the chance of hitting the race
is very remote and can only be hit if you are actively tracking the
heartbeat variable, which usually nobody does.
So, does it need to be taken care of or should it be considered
academic?
This sounds almost exactly like a repeat of the W95 bug that crashed it
at 49 days of uptime, Unforch for us, the only w95 in the house ran the
Associated presses news server for tv stations that ran their own news
depts. So we had to post a huge notice in the news dept offices that the
server machine had to be rebooted if the uptime went over 45 days. It
was otherwise an absolutely bulletproof system. Rather embarrassing to
lose the teleprompter, which it fed, in the middle of a 1 hour
newscast. Ancient history now of coarse, that was back when I ran the
tech side of WDTV-5 as the CE.
And it may be academic, I just checked my rp4b, which has 98 days of
uptime, still running and my go704 which has 159 days of uptime running
on a 4.19-rt kernal, both are fine although LCNC isn't running as LCNC
controls all power to both machines. LCNC not running=no power. I do
have a faint memory of leaving it running but disabled, and had to
reboot it once or twice in the past, using the rear power switch. So
I'd say if its an easy fix, do it.
Thanks Bertho.
--
Greetings Bertho
(disclaimers are disclaimed)
I have run hardware tests for up to 3 months or so.
What would the wrap of the heratbeat counter do?
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Peter Wallace
Mesa Electronics
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Cheers, Gene Heskett, CET.
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