I've been running RTlinux for about a month now, and three times so far
I've got an "RTL: lost 122711 jiffies" message. Subsequently the xntpd
daemon confirms that indeed the system has lost 1227 seconds of time
compared to UTC. The one time I was logged in, the machine did indeed hang
for about 20 minutes, and then came back to life of its own accord. The
suspicious thing is that 122711 jiffies is very close to 2^39 Pentium
clock ticks on this machine, so it sounds like an overflow problem
somewhere. Any ideas on what could be happening?
Details: Dell Pentium PII 450MHz, linux version 2.2.14-rtl2.3. I am
running an RTL module which schedules a periodic task at 5kHz to read
a ComputerBoards PCI-CTR05 counter card. Every 500 periods the task writes
the accumulated values to an RT-FIFO. The periodic task does disable
interrupts, but is always careful to limit the time spent with the
interrupt disabled. I use long longs everywhere to calculate time delays,
so numbers of size 2^39 should not cause a problem in my code. Is the
internal Pentium timer 40 bits?
thanks,
David
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David Buscher | Phone +44 1223 337302
Cavendish Laboratory, Madingley Road | Fax +44 1223 354599
Cambridge CB3 0HE, UK | http://www.mrao.cam.ac.uk/~dfb
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