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    SubjectRe: [RFC] Add support for semaphore-like structure with support for asynchronous I/O
    må den 04.04.2005 Klokka 12:22 (-0400) skreiv Benjamin LaHaise:

    > > Your approach looks reasonable and simple enough. It'd be useful if I
    > > could visualize the caller side of things as in the NFS client stream
    > > as you mention - do you plan to post that soon ?
    > > I'm tempted to think about the possibility of using your iosems
    > > with retry-based AIO.
    > I'm not sure I see the point in adding yet another type of lock to the
    > kernel that has different infrastructure. This will end up with much
    > more code changing to adapt to the new iosems, rather than just using a
    > new primative on the existing semaphores.

    The point is to avoid having to develop and test 23 different and highly
    arch-dependent (and hence non-maintainable) versions of the same code.
    In particular note that many of those architectures appear to be heavily
    over-optimized to directly inline assembly code as well as to use
    non-standard calling conventions. They all also manage somehow to differ
    w.r.t. spinlocking conventions and even w.r.t. the internal structures
    and algorithms used.

    IOW: the current semaphore implementations really all need to die, and
    be replaced by a single generic version to which it is actually
    practical to add new functionality.

    Failing that, it is _much_ easier to convert the generic code that needs
    to support aio to use a new locking implementation and then test that.
    It is not as if conversion to aio won't involve changes to the code in
    the area surrounding those locks anyway.

    Trond Myklebust <>

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