13 Jul
2004
13 Jul
'04
8 p.m.
From: "Christian Henz" <chrhenz(a)gmx.de>
On Tue, Jul 13, 2004 at 10:55:48AM -0400, Paul Davis
wrote:
Hmm, I've just recently learned about the Priority Ceiling Protocol,
an extension to Priority Inversion Protocol, which explicitly prevents
deadlocks. And I've learned about both in a RTOS course, so I'm a little
surprised by your statement about them not being useful for RT purposes :-)
They are meant for realtime use and are part of the POSIX realtime
extensions, so I disagree with Paul. That's not uncommon, though we
have agreed on some things in the past. :)
--ms
Thus, the
fact that Linux does not support protocols to prevent priority
inversion (please correct me if I am wrong) kind of suggests that supporting
realtime applications is not considered very important.
we went through this (you and i in particular) right here on LAD a
year or so ago. while i might agree with you about the priority given
to RT-ish apps, my recollection of the end of that discussion is that
priority inheritance is neither necessary nor sufficient to allow
adequate RT performance. priority inversion generally can be factored
out through application redesign, and the protocols i've seen to
address it are not useful for RT purposes - they just help deadlock.