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    SubjectRe: [take24 0/6] kevent: Generic event handling mechanism.
    Evgeniy Polyakov wrote:
    > Why do we want to inject _ready_ event, when it is possible to mark
    > event as ready and wakeup thread parked in syscall?

    Going back to this old one:

    How do you want to mark an event ready if you don't want to introduce
    yet another layer of data structures? The event notification happens
    through entries in the ring buffer. Userlevel code should never add
    anything to the ring buffer directly, this would mean huge
    synchronization problems. Yes, one could add additional data structures
    accompanying the ring buffer which can specify userlevel-generated
    events. But this is a) clumsy and b) a pain to use when the same ring
    buffer is used in multiple threads (you'd have to have another shared
    memory segment).

    It's much cleaner if the userlevel code can get the kernel to inject a
    userlevel-generated event. This is the equivalent of userlevel code
    generating a signal with kill().

    --
    ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖

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