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    SubjectRe: [PATCH] mm: skip zombie in OOM-killer
    From
    2011/3/7 David Rientjes <rientjes@google.com>:
    > On Sun, 6 Mar 2011, KOSAKI Motohiro wrote:
    >
    >> > When we check that task has flag TIF_MEMDIE, we forgot check that
    >> > it has mm. A task may be zombie and a parent may wait a memor.
    >> >
    >> > v2: Check that task doesn't have mm one time and skip it immediately
    >> >
    >> > Signed-off-by: Andrey Vagin <avagin@openvz.org>
    >>
    >> This seems incorrect. Do you have a reprodusable testcasae?
    >> Your patch only care thread group leader state, but current code
    >> care all thread in the process. Please look at oom_badness() and
    >> find_lock_task_mm().
    >>
    >
    > That's all irrelevant, the test for TIF_MEMDIE specifically makes the oom
    > killer a complete no-op when an eligible task is found to have been oom
    > killed to prevent needlessly killing additional tasks.  oom_badness() and
    > find_lock_task_mm() have nothing to do with that check to return
    > ERR_PTR(-1UL) from select_bad_process().
    >
    > Andrey is patching the case where an eligible TIF_MEMDIE process is found
    > but it has already detached its ->mm.  In combination with the patch
    > posted to linux-mm, oom: prevent unnecessary oom kills or kernel panics,
    > which makes select_bad_process() iterate over all threads, it is an
    > effective solution.

    Probably you said about the first version of my patch.
    This version is incorrect because of
    http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=dd8e8f405ca386c7ce7cbb996ccd985d283b0e03

    but my first patch is correct and it has a simple reproducer(I
    attached it). You can execute it and your kernel hangs up, because the
    parent doesn't wait children, but the one child (zombie) will have
    flag TIF_MEMDIE, oom_killer will kill nobody


    The link on the first patch:
    http://groups.google.com/group/linux.kernel/browse_thread/thread/b9c6ddf34d1671ab/2941e1877ca4f626?lnk=raot&pli=1
    >
    > Thanks.
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