BOUNCE rtl@rtlinux.org: Approval required: Non-member submission from [yodaiken@hq2.fsmlabs.com] (fwd)

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>From owner-rtl Thu May  3 14:49:36 2001
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From: yodaiken@hq2.fsmlabs.com
Date: Thu, 3 May 2001 14:42:52 -0600
To: tfolkers@hamms.as.arizona.edu
Cc: rtl@fsmlabs.com, yodaiken@fsmlabs.com
Subject: Re: [rtl] do_gettimeofday().
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References: <200105022112.f42LC0417422@hamms.as.arizona.edu> <3AF19D99.2B3107F9@opersys.com>
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In-Reply-To: <3AF19D99.2B3107F9@opersys.com>; from karym@opersys.com on Thu, May 03, 2001 at 02:04:09PM -0400


What version of RTL and what processor has the time gain?
clock_gettime is better than do_gettime since it is 
the POSIX call and will work on RTbsd as well as RTLinux. 
We should just fix the gettime if that's not correct.


> Thomas Folkers wrote:
> > 
> > Victor,
> >   How come I can't get the time of day from the kernel? If I use
> > do_gettimeofday(), eventually the system will hang. It may not happen
> > right away, but it will hang. I'm trying to time external events and
> > record the exact time an interrupt comes in and the only way to compare
> > that time to other events and to other systems is to have the exact
> > system time. The clock_gettime() routine returns something close to
> > the real system clock time, but then proceeds to gain time at the rate of
> > 35,000 nsecs/sec. That's probably due to a miss calibration in the cpu HZ
> > value. I have looked over the rtl_time.c file and can see where you 'sync'
> > the CLOCK_REALTIME to the results of a do_gettimeofday() call, but then
> > there doesn't seem to be any other 'tweeks' to the time to keep it in
> > sync. So, while the clock_gettime() produces a nice monotonic clock, it
> > bear little resemblance to actual time.
> >   So, how do I get the time of day from the kernel?
> > 
> > Thanks for you help,
> > Tom
> > 
> > --
> > 
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> -- 
> ===================================================
>                  Karim Yaghmour
>                karym@opersys.com
>       Embedded and Real-Time Linux Expert
> ===================================================