3 ms·
I agree, there are operating systems where few guarantees are made about protection from priority inversion, at least not without specific programmer interventi
by RossBencina 7y ago
I agree, there are operating systems where few guarantees are made about protection from priority inversion, at least not without specific programmer intervention. As a programmer you need to be aware that priority inversion can be a thing.
However, this has no bearing on whether or not priority inversion is a "solved problem". "Solved problem" generally means that there are well known, widely studied technical solutions to a problem. My understanding right now is that priority inversion is a solved problem -- it is a standard topic in any introductory textbook on real-time systems with solutions that I stated. But maybe I'm wrong -- certainly the author seems to think so -- hence my question stands: I would like to understand why priority inversion is not a solved problem.
- MaxBarraclough 7y ago> hence my question stands: I would like to understand why priority inversion is not a solved problem. I believe it's because although complete solutions do exist, they have prohibitive overheads. Annoyingly I can't find the relevant paper I'm thinking of.
- Dobiasd 7y ago> I would like to understand why priority inversion is not a solved problem. Maybe I just was not careful enough in choosing this phrasing when writing the article. Do you think it would make sense if I change "but it's far from being solved once and for all." to "each of them with different upsides and downsides."?
- RossBencina 7y agoTrade offs yes. I think I understand now that you meant that it is common that application-level priority inversion is not automatically avoided by the OS -- programmers still need to worry about it. Even if theoretical solutions exist, they may not be available on your chosen platform, or they may need to be manually configured (e.g. PTHREAD_PRIO_INHERIT).
- Dobiasd 7y agoThanks. I committed a change (https://github.com/Dobiasd/articles/commit/8ac8db11eb95de688abbe1e8975e0d40a428df83 https://github.com/Dobiasd/articles/commit/8ac8db11eb95de688...). Feel free to open a PR if you have a better phrasing in mind. :)
- MaxBarraclough 7y agoSorry to double-reply, but the paper I was thinking of was probably [0] It seems very informative. Doesn't appear to be peer-reviewed, mind. [0] http://www.cse.uaa.alaska.edu/~ssiewert/a320_doc/Yodaiken-2004-Against%20priority%20inheritance.pdf http://www.cse.uaa.alaska.edu/~ssiewert/a320_doc/Yodaiken-20...