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    From
    SubjectRe: Killing clones
    Date
    Followup to:  <Pine.LNX.3.95.970814090203.21030C-100000@vuser.vu.union.edu>
    By author: Rob Hagopian <hagopiar@vuser.vu.union.edu>
    In newsgroup: linux.dev.kernel
    >
    > > About a year ago a least was a a discussion about fixing up the
    > > CLONE_PID flag so that thread id's would be encoded in the upper bits of
    > > the pid. One could have ps list only the proc info for the initial
    > > thread (or other thread if the initial has exited), and be able to see
    > > what initial process all the threads are associated with.
    >
    > So if 32-bit [real] PIDs come around (there was talk of them appearing in
    > 2.1.x, and it's something I think a few people would like to see) then
    > we'd have 48 or 64 bit PIDs with thread info?
    > -Rob H.
    >

    Note: there is actually no need for tid's to be allocated from a
    larger pool than pid's, although that may possibly allow some
    optimizations (I am not 100% convinced, since I think the kernel would
    have to validate all assumptions explicitly.)

    You could very well allocate them out of the same number pool; if you
    do *not* specify CLONE_PID then you allocate both a pid and a tid, if
    you do, then you allocate a tid only. That would mean that tid's
    wouldn't "look" any different than pid's, but the kernel would still
    know.

    For example: process - 47 threads - 48, 57, 122
    process - 90 threads - 91, 94, 102, 107, 121
    process - 92 threads - 93

    (The last process being single-threaded.)

    -hpa
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