Approaches to realtime Linux
Posted Oct 15, 2004 1:35 UTC (Fri) by karim
In reply to: Approaches to realtime Linux
Parent article: Approaches to realtime Linux
The main reason I don't like RTAI/Fusion is that you have to make special drivers for it. If the real-time is included in the kernel you would "only" have to review the drivers and subsystems you want to call directly from you real-time threads and check their behaviour wrt. real-time. The obligation of the rest of the system is that it only holds spinlocks for a very short time and otherwise use mutexes as locks.
The point is as I made it before: for many developers, including driver developers, the kernel's behavior is not entirely clear. Add a new API and people will use it, and it will find its way into "normal" Linux drivers. And once it's everywhere we'll still be at square one in regards to finding who's influencing the latency ... The solution to this problem is to provide a very basic API that provides hard-rt while not being as simple to use as just yet another locking scheme. I believe the Adeos interrupt pipeline does this quite well for the reasons I have enumerated elsewhere, and it changes nothing to kernel's current behavior.
It is up to companies like MontaVista to test how you can change the various parameters and they can earn their living by selling that knowledge. It is also their job to check that the various subsystems behave nicely wrt. locking. Forinstance, if somebod...
Sorry, the Linux community is not about depending on any distro. The fact of the matter is that whatever new feature finds itself in the kernel out to be accessible to anyone out there who cares about that type of functionality, regardless of whether he uses Debian, MV, or if he/she builds his own from scratch.
Notice that, as Jonathan points out, the existing minimal preemption functionality that's already there has not yet been adopted by all kernel developers. Certainly trying to sell this new preemption on steriods by making the case that distros will audit the kernel for their clients is likely to be received coldly.
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