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    From
    SubjectRe: [PATCH] Linux-2.5 fix/improve get_pid()
    Date
    Followup to:  <Pine.LNX.4.44.0208081312330.8705-100000@home.transmeta.com>
    By author: Linus Torvalds <torvalds@transmeta.com>
    In newsgroup: linux.dev.kernel
    >
    > Guys, this discussion is getting ridiculous.
    >
    > Doing a bit allocator should be trivial, but it's hard to know when a bit
    > is to be free'd. You can't just do it at "exit()" time, because even if
    > pid X exits, that doesn't mean that X can be re-used: it may still be used
    > as a pgid or a tid by some other process Y.
    >
    > So if you really want to take this approach, you need to count the uses of
    > "pid X", and free the bitmap entry only when that count goes to zero. I
    > see no such logic in Bill Irwin's code, only a comment about last use
    > (which doesn't explain how to notice that last use).
    >

    Even so, we need to maintain Not Recently Used semantic. A discussion
    on #kernel seems to have ended up with recommending a design target of
    "no pid reuse within 30 seconds", with 1 second being an absolute
    requirement.

    -hpa
    --
    <hpa@transmeta.com> at work, <hpa@zytor.com> in private!
    "Unix gives you enough rope to shoot yourself in the foot."
    http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com>
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