From: Karim Yaghmour <karim@opersys.com>
To: "Ph. Marek" <marek@bmlv.gv.at>
Cc: linux-kernel@vger.kernel.org, Richard Moore <richardj_moore@uk.ibm.com>
Subject: Re: AGAIN: Re: gettimeofday clock jump bug (on AMD 756)
Date: Fri, 30 Aug 2002 20:50:52 -0400 [thread overview]
Message-ID: <3D7012EC.C1FEF112@opersys.com> (raw)
In-Reply-To: 200208291200.54694.marek@bmlv.gv.at
"Ph. Marek" wrote:
> The difference is both times about 4295 seconds - so I think that the problem
> has something to do with 2^32 microseconds.
This 2^32 jump is consistent with the jumps I saw.
I was discussing this issue with Richard Moore (IBM) a couple of weeks
ago and he mentionned that they had seen a similar problem with OS/2.
In that case, the problems were due to the time it took to read some
timer register. In other words, there may be a short time-window where
the values available are valid and nothing is garanteed if we exceed this
time-window. (This is second hand and I may have misunderstood a couple
of details, so I attached Richard so he can confirm/deny what I'm saying
here.)
Linux reads the PIT (8253) every 10ms on a PC, so the question is:
anyone know about 8253 reading deadlines ?
Karim
===================================================
Karim Yaghmour
karim@opersys.com
Embedded and Real-Time Linux Expert
===================================================
prev parent reply other threads:[~2002-08-31 0:47 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-08-29 10:00 AGAIN: Re: gettimeofday clock jump bug (on AMD 756) Ph. Marek
2002-08-31 0:50 ` Karim Yaghmour [this message]
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