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[Der Herr Hofrat <der.herr@hofr.at>]

>From owner-rtl Thu May 10 01:06:36 2001
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Date: Thu, 10 May 2001 09:04:15 +0200
From: =?iso-8859-1?Q?S=E9bastien?= GAUME <sgaume@b2i-toulouse.com>
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To: rtl@fsmlabs.com, rtl@rtlinux.org, yodaiken@fsmlabs.com
Subject: Re: [rtl] Nanosleep and priority
References: <3AF9123A.F7EA2DE1@b2i-toulouse.com> <20010509062023.A10023@hq2>
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Well, each time a task wakes up or goes to sleep, it asks for the date. In
fact, I do :

start_time = gethrtime();
nanosleep(&rqtp,&rmtp); // with rqtp.tv_nsec = 2000000
end_time = gethrtime();

That's how I can check when the tasks really wake up and how long they last.
The results show me that they last about the expected 2 ms, that they wake up
every 5 ms and that ... the task with the lower priority level wakes up 20 us
after the other. It makes me think that the first task is still running.

I still don't know what's wrong with that.

Sebastien

Victor Yodaiken a ecrit :

> Are you sure that the first task is still running?
>
> On Wed, May 09, 2001 at 11:47:38AM +0200, S?bastien GAUME wrote:
> > Hello !
> >
> > I've come across surprising results while using the nanosleep function
> > in my realtime tasks. I wrote a program in which two tasks are created.
> > Both are periodic (running under the oneshot mode, period = 5 ms), are
> > supposed to start at the same time and should last 2 ms. One has a
> > greater priority level then the other. And I'm aiming to check if the
> > realtime scheduling works well.
> >
> > What  really surprises me is that the task with the lower priority level
> >
> > always starts about 20 us after the first task ! At that moment, this
> > task is not supposed being able to wake up and to start...
> >
> > I  feel the impression that the realtime tasks behave as if there is no
> > realtime scheduling, although the fifo realtime scheduling should be on
> > and work.
> >
> > So, I you have any idea of what the problem could be,...
> >
> > Thank you
> >
> > Sebastien
> >
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