On Wed, 13 Jan 2016, Tetsuo Handa wrote: > David Rientjes wrote: > > > @@ -171,7 +195,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, > > > if (oom_unkillable_task(p, memcg, nodemask)) > > > return 0; > > > > > > - p = find_lock_task_mm(p); > > > + p = find_lock_non_victim_task_mm(p); > > > if (!p) > > > return 0; > > > > > > > I understand how this may make your test case pass, but I simply don't > > understand how this could possibly be the correct thing to do. This would > > cause oom_badness() to return 0 for any process where a thread has > > TIF_MEMDIE set. If the oom killer is called from the page allocator, > > kills a thread, and it is recalled before that thread may exit, then this > > will panic the system if there are no other eligible processes to kill. > > > Why? oom_badness() is called after oom_scan_process_thread() returned OOM_SCAN_OK. > oom_scan_process_thread() returns OOM_SCAN_ABORT if a thread has TIF_MEMDIE set. > oom_scan_process_thread() checks for TIF_MEMDIE on p, not on p's threads. If one of p's threads has TIF_MEMDIE set and p does not, we actually want to set TIF_MEMDIE for p. That's the current behavior since it will lead to p->mm memory freeing. Your patch is excluding such processes entirely and selecting another process to kill unnecessarily. -- 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>