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    SubjectRe: [PATCH] mm: skip zombie in OOM-killer
    Date
    > 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

    OK. I can ack this.
    TIF_MEMDIE mean the process have been receive SIGKILL therefore we can assume it
    as per process flag.



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