QNX 4 - semaphores and priority inversion / inheritance

QNX Newsgroups (Archives) qdn.public.qnx4
1

Hi,
I am trying to demonstrate the MARS pathfinder problem (see my homepage
under “know how”) withing QNX 4 training course. I would like to do that the
most realistic way. The idea is to use semaphores. Do these behave with
priority inversion problem or without
(I would like to swap from priority inversion to priority inheritance during
the training).

Any prompt answer appreciated
tia
Jörg

–

http://www.ibk-consult.de

2

any answer to the above problem?
Jörg

–

IBK-Consult for Real-Time
http://www.ibk-consult.de
===== QNX is for Real-Time: http://www.qnx.com ====


“IBK” <joerg.kampmann@ibk-consult.de> schrieb im Newsbeitrag
news:abea95$oor$1@inn.qnx.com…

Hi,
I am trying to demonstrate the MARS pathfinder problem (see my homepage
under “know how”) withing QNX 4 training course. I would like to do that
the
most realistic way. The idea is to use semaphores. Do these behave with
priority inversion problem or without
(I would like to swap from priority inversion to priority inheritance
during
the training).

Any prompt answer appreciated
tia
Jörg

–

http://www.ibk-consult.de
\

3

IBK <joerg.kampmann@ibk-consult.de> wrote:

any answer to the above problem?

Semaphores don’t transmit priority information, so you could
create a priority inversion with them.

Message passing, by default, doesn’t transmit priority information,
but the receiving process can set the _PPF_PRIORITY_FLOAT flag using
the qnx_pflags() call, and have message transmit priority information,
thereby preventing the priority inversion problem.

So, if you want to demonstrate a before & after, message passing
might be better than semaphores.

-David

Joerg

–

IBK-Consult for Real-Time
http://www.ibk-consult.de
===== QNX is for Real-Time: > http://www.qnx.com > ====



“IBK” <> joerg.kampmann@ibk-consult.de> > schrieb im Newsbeitrag
news:abea95$oor$> 1@inn.qnx.com> …
Hi,
I am trying to demonstrate the MARS pathfinder problem (see my homepage
under “know how”) withing QNX 4 training course. I would like to do that
the
most realistic way. The idea is to use semaphores. Do these behave with
priority inversion problem or without
(I would like to swap from priority inversion to priority inheritance
during
the training).

Any prompt answer appreciated
tia

–

http://www.ibk-consult.de

\

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