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    From
    SubjectRe: init's children list is long and slows reaping children.
    Date
    Ingo Molnar <mingo@elte.hu> writes:

    > * Eric W. Biederman <ebiederm@xmission.com> wrote:
    >
    >> > so ... is anyone pursuing this? This would allow us to make
    >> > sys_wait4() faster and more scalable: no tasklist_lock bouncing for
    >> > example.
    >>
    >> which part?
    >
    > all of it :) Everything you mentioned makes sense quite a bit. The
    > thread signal handling of do_wait was added in a pretty arbitrary
    > fashion so i doubt there are strong requirements in that area. Apps
    > might have grown to get used to it meanwhile though, so we've got to do
    > it carefully.

    I'm looking at. If only because there is a reasonable chance doing this
    will fix the races with a threaded init.

    However I just found something nasty. The wait __WNOTHREAD flag.

    And my quick search seems to find at least one user space applications
    that uses it, and it is widely documented so I suspect there are
    others :(

    I played with moving the lists into signal_struct, and short of
    architecture specific users of task->children all I had to touch
    were:

    include/linux/init_task.h | 2 +-
    include/linux/sched.h | 5 +-
    kernel/exit.c | 159 +++++++++++++++++++++------------------------
    kernel/fork.c | 2 +-
    mm/oom_kill.c | 4 +-

    So it should be relatively easy to change this child lists around...

    Eric
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