Re: Problems with wait queues

From: Richard B. Johnson (
Date: Wed Jun 26 2002 - 09:17:45 EST

On Wed, 26 Jun 2002, Nicolas Bougues wrote:

> On Wed, Jun 26, 2002 at 12:52:41PM +0200, Andries Brouwer wrote:
> > On Wed, Jun 26, 2002 at 12:32:43PM +0200, Nicolas Bougues wrote:
> >
> > > Does anybody have any idea on what I may have done wrong, and why
> > > would loadavg increase when vmstat show no activity ?
> >
> > loadavg does not report what you think it reports
> >
> As far as I understand, loadavg reports the average number of
> processes in the TASK_RUNNING state.
> What happens in my driver, I believe, is that :
> - on timer interrupt, I do some stuff, and wake_up the waiting process
> - then the loadavg is computed (seeing my waiting task as TASK_RUNNING)
> - then the scheduler runs the task
> - then the task goes immediatly back to sleep
> >From this point of view, then my problem is just "cosmetic". Isn't
> there a way to do things in a different order, so that I could still
> get a meaningful(*) loadavg ?
> (*): by meaningful, I mean representing the number of busy processes
> at a random point in time.
> --
> Nicolas Bougues

I am sure that you can have things look correct as well as run
properly. However, you didn't show us the code. You need to
do something like:


while your wake-up occurs with:


Or, you can do (the hard way) :

                 current->policy |= SCHED_YIELD;

Both ways (and others) will look fine with `top` and will sleep

Dick Johnson

Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).

                 Windows-2000/Professional isn't.

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