Michal Hocko wrote: > On Fri 10-06-16 00:15:18, Tetsuo Handa wrote: > [...] > > Nobody will set MMF_OOM_REAPED flag if can_oom_reap == true on > > CONFIG_MMU=n kernel. If a TIF_MEMDIE thread in CONFIG_MMU=n kernel > > is blocked before exit_oom_victim() in exit_mm() from do_exit() is > > called, the system will lock up. This is not handled in the patch > > nor explained in the changelog. > > I have made it clear several times that !CONFIG_MMU is not a target > of this patch series nor other OOM changes because I am not convinced > issues which we are trying to solve are real on those platforms. I > am not really sure what you are trying to achieve now with these > !CONFIG_MMU remarks but if you see _real_ regressions for those > configurations please describe them. This generic statements when > CONFIG_MMU implications are put into !CONFIG_MMU context are not really > useful. If there are possible OOM killer deadlocks without this series > then adding these patches shouldn't make them worse. > > E.g. this particular patch is basically a noop for !CONFIG_MMU because > use_mm() is MMU specific. It is also highly improbable that a task would > share mm with init... But this is not safe for CONFIG_MMU=y kernels as well. can_oom_reap == false means that oom_reap_task() will not be called. It is possible that the TIF_MEMDIE thread falls into atomic_read(&task->signal->oom_victims) > 0 && find_lock_task_mm(task) == NULL situation. We are still risking OOM livelock. We must somehow clear (or ignore) TIF_MEMDIE even if oom_reap_task() is not called. Can't we apply http://lkml.kernel.org/r/201606102323.BCC73478.FtOJHFQMSVFLOO@xxxxxxxxxxxxxxxxxxx now? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>