2011/3/7 David Rientjes <rientjes@xxxxxxxxxx>: > 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@xxxxxxxxxx> >> >> 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. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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