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    SubjectRe: [patch 7/8] fdmap v2 - implement sys_socket2

    On Thu, 7 Jun 2007, Matt Mackall wrote:
    > First, how does this work in-kernel? Does it set a flag in the thread
    > struct that magically gets used in the actual syscall? Or do we pass
    > flags down to the sys_foo() function in some manner?

    Set a flag in the thread-struct.

    In fact, that's how "access()" already works.

    And yes, syslets would need to have their own thread-structs and/or
    save/restore the thing.

    > Second, I think we're likely to run out of flag bits really quickly as
    > this is a good dumping spot for patching up our many slightly
    > brain-damaged APIs (be they POSIX or Linux-specific).

    Well, I do suspect that we'd need to basically make the flags be
    per-system call. With "common features" (ie a system call that doesn't
    return a file descriptor would re-use the bit for "nonlinear-fd" for
    something else, while a system call that doesn't do path lookup would use
    all the LOOKUP_xyzzy bits for something else).

    I agree that if we kept flags _totally_ separate, we'd run out of them
    really quickly. But I don't think we want to ever be in the situation
    where _one_ set of system calls would need that many flags. If we get
    there, we'd really be much better off with a new system call!

    > Third, can I do sys_indirect(sys_indirect(foo, args), flags1), flags2)?

    I'd say no.

    > Fourth, can we do sys_indirect(foo, args, flags | ASYNC) and get most
    > of the way to merging this with the syslet proposal?

    I think that may well be a really good idea.

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      Last update: 2007-06-08 04:29    [W:0.020 / U:13.680 seconds]
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