Re: patent on O_ATOMICLOOKUP [Re: [PATCH] loopable tmpfs (2.4.17)]

Oliver Xymoron
2002-05-26T03:12:13Z

On Sat, 25 May 2002, Linus Torvalds wrote:

>
>
> On Sat, 25 May 2002, Linus Torvalds wrote:
> >
> > Can we make the whole kernel truly hard-RT? Sure, possible in theory. In
> > practice? No way, José. It's just not mainline enough.
>
> Side note: we could, of course, mark some spinlocks (and thus some
> code-paths) as being RT-safe, and then make sure that those spinlocks -
> when they disable interrupts - actually disable the _hw_ interrupts even
> with the RT patches.
>
> That would make those sequences usable even from within a RT subset, but
> would obviously mean that those spinlocks have to be checked for latency
> issues - because any user (also non-RT ones) would obviously be truly
> uninterruptible within these spinlocks.

I'm sure you know this route is not very useful - there's practically
nothing that we can push across the hard RT divide anyway. We can't do
meaningful filesystem I/O, memory allocation, networking, or VM fiddling -
what's left?

Cleaning up soft RT latencies will make the vast majority of people who
think they want hard RT happy anyway.

--
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