Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [PATCH] mm: skip zombie in OOM-killer | Date | Tue, 8 Mar 2011 10:24:52 +0900 (JST) |
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> 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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