Re: Priority Inversion/Inheritance in Linux Kernel

["Peter Teoh" <htmldeveloper@xxxxxxxxx>]

Thank you Rene, one last scenario:

On 7/5/08, Rene Herman <rene.herman@xxxxxxxxxxxx> wrote:
> On 04-07-08 18:28, Peter Teoh wrote:
>
>
> > And for the phenomena of "unbounded priority inversion", I found this
> > very useful:
> >
> > http://lkml.org/lkml/2006/5/10/52
> >
> > Thank you to Rene and Roberto for the discussion.....
> >
>
>  Just a final note; note that the above linked document does use a slightly
> different definition of priority inversion then I did.
>
>  It already calls the high-prio process blocking because the low-prio
> process is holding a lock "priority inversion" while I in fact sort of
> insist on not doing that -- only call the _medium_ prio process having an
> effectively higher priority than the high-prio process "priority inversion".
>

So what I can deduce is that (another variation):

If there is a low prio + medium prio process running.......and only
these two....no problem.   So what  if another process with "high
prio" now comes in - that will also creates a problem right?

Or  similarly two process - medium + high prio running, and now comes
another low prio process - that will also be a  problem, right?

Essentially, the original algorithm (without priority inversion) can
only be used for two level priority processing, but once another level
(in between, higher or  lower) comes in, problem comes, correct?

>  I do so because if you do it like the linked document you'll have to
> describe priority inversion as "generally not a problem and the expected and
> designed way of things" and this causes confusion. Priority inversion is
> really only ever discussed in the context of it being a problem, so let's
> make sure our definition agrees with that.
>
>  But definitions are up for grabs ofcourse and whichever one will do as long
> as you remember the problem scenario...
>
>  Rene.
>

-- 
Regards,
Peter Teoh

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