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    SubjectRe: [patch 00/11] ANNOUNCE: "Syslets", generic asynchronous system call support
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    Hi Ingo,

    On Tuesday 13 February 2007 15:39, Ingo Molnar wrote:
    >
    > * Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote:
    >
    > > > What are the semantics of async sys_async_wait and async sys_async ?
    > >
    > > Ooooohh. OpenVMS lives forever ;) Me likeee ;)
    >
    > hm, i dont know OpenVMS - but googled around a bit for 'VMS
    > asynchronous' and it gave me this:
    >
    > http://en.wikipedia.org/wiki/Asynchronous_system_trap
    >
    > is AST what you mean? From a quick read AST seems to be a signal
    > mechanism a bit like Unix signals, extended to kernel-space as well -
    > while syslets are a different 'safe execution engine' kind of thing
    > centered around the execution of system calls.
    >

    That is only one of ways of notifying userspace of system call completion
    on OpenVMS. Pretty much every syscall there exists in 2 flavors - async
    and sync, for example $QIO and $QIOW or $ENQ/$ENQW (actually -W flavor
    is async call + $SYNCH to wait for completion). Once system service call
    is completed the OS would raise a so-called event flag and may also
    deliver an AST to the process. Application may either wait for an
    event flag/set of event flags (EFN) or rely on AST to get notification.

    --
    Dmitry
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