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    SubjectRe: Preempting kernel tasks
    Date
    On Thu, 5 Sep 1996, Linus Torvalds wrote:

    > Like David, I do not like the idea of pre-empting kernel tasks. It implies a
    > more complex locking setup than I'd really like.

    I think any realtime task should be able to preempt the kernel,
    while the realtime task executes code in the USER-SEGMENT.
    If the task does a System call, the control has to be given
    back to the task, which holds the kernel lock.
    This would give a very fast response which is required by
    realtime tasks, if the realtime-task uses locked memory.

    I think this change should cause no problems. As far as
    I know its already possible to execute code in a tasks User
    Segment while a second processor executes Kernel-Code
    in SMP-Linux, so why not doing something similar with
    a single processor ?

    > HOWEVER, I'm all for having "user processes" in kernel mode. That's not too
    > hard - if only implies that we have to change the way we test for "user vs
    > kernel" a bit.

    This in combination with my above suggestion would make possible
    very nice realtime tasks.

    What do You think about this ?

    Jochen

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    Jochen Karrer
    http://cip.physik.uni-wuerzburg.de/~cip307

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