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

    --
    "Love the dolphins," she advised him. "Write by W.A.S.T.E.."

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