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    SubjectRe: O_NONBLOCK is NOOP on block devices
    Hi Jeff,

    > I guess I should note that I've suggested nonblocking I/O for files
    > before:
    >
    > http://linux.derkeiler.com/Mailing-Lists/Kernel/2004-10/0290.html
    >
    > I'll also note that enabling such a patch broke apps that accessed cd
    > burners, for example, since O_NONBLOCK had some preexisting semantics
    > there that I fail to recall.

    Sounds like nonblocking read/write calls are strongly tied to threads
    instead of state related to a file descriptor. I haven't poked around
    in there, but perhaps the current linux io architecture is just too
    set in stone to design an efficient non blocking mechanism. It would
    be a shame not to fix it simply because some broken apps depend upon
    blocking behavior when they have been explicitly specifying O_NONBLOCK
    via open or fcntl.

    At least for now we can describe it's actual behavior in the man
    pages; I will be submitting a man page patch for consideration later
    today.

    - Mike


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