Messages in this thread | | | Date | Sat, 25 May 2002 11:44:39 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: patent on O_ATOMICLOOKUP [Re: [PATCH] loopable tmpfs (2.4.17)] |
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On Sat, 25 May 2002, Karim Yaghmour wrote: > > Blinders ehh... Well, if you would care to ask I would answer. > > In reality, what you point out is actually a non-issue since the hard-rt > user-land tasks are not allowed to call on normal Linux services. They > can only call on RTAI services which are exported by an extra soft-int. > These services are hard-rt, so there's no problem there.
.. which was exactly what I said:
"..every single spinlock in the kernel assumes that the kernel isn't preempted, which means that user apps that can preempt the kernel cannot use them."
Karim, I don't _need_ to download RTAI or ask you questions about how it works, because this is fundamental "RT-101" stuff. This is what priority inversion is all about: if you make user land more important than the kernel, it _cannot_ stay RT and use kernel services.
I went on to say:
"Karim claims to give "user land" hard-real-time abilities, but the fact is, it's not "user land" any more. it's a limited shadow, and a _perversion_ of what user land is supposed to be all about."
Which certainly should have told you that I understood the limitations of RTAI very well indeed. And I reject them.
Linus
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